<s>
BitTorrent	B-Protocol
is	O
a	O
communication	O
protocol	O
for	O
peer-to-peer	O
file	O
sharing	O
(	O
P2P	O
)	O
,	O
which	O
enables	O
users	O
to	O
distribute	O
data	B-General_Concept
and	O
electronic	B-Operating_System
files	I-Operating_System
over	O
the	O
Internet	O
in	O
a	O
decentralized	O
manner	O
.	O
</s>
<s>
To	O
send	O
or	O
receive	O
files	O
,	O
users	O
use	O
a	O
BitTorrent	B-Protocol
client	O
on	O
their	O
Internet-connected	O
computer	O
.	O
</s>
<s>
A	O
BitTorrent	B-Protocol
client	O
is	O
a	O
computer	O
program	O
that	O
implements	O
the	O
BitTorrent	B-Protocol
protocol	I-Protocol
.	O
</s>
<s>
BitTorrent	B-Protocol
clients	O
are	O
available	O
for	O
a	O
variety	O
of	O
computing	B-Device
platforms	I-Device
and	O
operating	B-General_Concept
systems	I-General_Concept
,	O
including	O
an	B-Protocol
official	I-Protocol
client	I-Protocol
released	O
by	O
Rainberry	O
,	O
Inc	O
.	O
Popular	O
clients	O
include	O
μTorrent	B-Application
,	O
Xunlei	B-Protocol
Thunder	O
,	O
Transmission	B-Language
,	O
qBittorrent	B-Application
,	O
Vuze	B-Application
,	O
Deluge	B-Language
,	O
BitComet	B-Protocol
and	O
Tixati	B-Protocol
.	O
</s>
<s>
BitTorrent	B-Protocol
trackers	I-Protocol
provide	O
a	O
list	O
of	O
files	O
available	O
for	O
transfer	O
and	O
allow	O
the	O
client	O
to	O
find	O
peer	O
users	O
,	O
known	O
as	O
"	O
seeds	O
"	O
,	O
who	O
may	O
transfer	O
the	O
files	O
.	O
</s>
<s>
On	O
15	O
May	O
2017	O
,	O
BitTorrent	B-Protocol
,	O
Inc	O
.	O
(	O
later	O
renamed	O
Rainberry	O
,	O
Inc	O
.	O
)	O
released	O
BitTorrent	B-Protocol
v2	O
protocol	O
specification	O
.	O
</s>
<s>
libtorrent	B-Language
was	O
updated	O
to	O
support	O
the	O
new	O
version	O
on	O
6	O
September	O
2020	O
.	O
</s>
<s>
BitTorrent	B-Protocol
is	O
one	O
of	O
the	O
most	O
common	O
protocols	O
for	O
transferring	O
large	O
files	O
,	O
such	O
as	O
digital	O
video	O
files	O
containing	O
TV	O
shows	O
and	O
video	O
clips	O
,	O
or	O
digital	O
audio	O
files	O
containing	O
songs	O
.	O
</s>
<s>
BitTorrent	B-Protocol
was	O
responsible	O
for	O
3.35	O
%	O
of	O
all	O
worldwide	O
bandwidth	O
—	O
more	O
than	O
half	O
of	O
the	O
6%	O
of	O
total	O
bandwidth	O
dedicated	O
to	O
file	O
sharing	O
.	O
</s>
<s>
In	O
2019	O
,	O
BitTorrent	B-Protocol
was	O
a	O
dominant	O
file	O
sharing	O
protocol	O
and	O
generated	O
a	O
substantial	O
amount	O
of	O
Internet	O
traffic	O
,	O
with	O
2.46	O
%	O
of	O
downstream	O
,	O
and	O
27.58	O
%	O
of	O
upstream	O
traffic	O
.	O
</s>
<s>
,	O
BitTorrent	B-Protocol
had	O
15	O
–	O
27million	O
concurrent	O
users	O
at	O
any	O
time	O
.	O
</s>
<s>
,	O
BitTorrent	B-Protocol
is	O
utilized	O
by	O
150	O
million	O
active	O
users	O
.	O
</s>
<s>
The	O
use	O
of	O
BitTorrent	B-Protocol
may	O
sometimes	O
be	O
limited	O
by	O
Internet	O
Service	O
Providers	O
(	O
ISPs	O
)	O
,	O
on	O
legal	O
or	O
copyright	O
grounds	O
.	O
</s>
<s>
Users	O
may	O
choose	O
to	O
run	O
seedboxes	O
or	O
virtual	B-Application
private	I-Application
networks	I-Application
(	O
VPNs	B-Application
)	O
to	O
circumvent	O
these	O
restrictions	O
.	O
</s>
<s>
The	O
first	O
release	O
of	O
the	O
BitTorrent	B-Protocol
client	O
had	O
no	O
search	B-Application
engine	I-Application
and	O
no	O
peer	O
exchange	O
.	O
</s>
<s>
Up	O
until	O
2005	O
,	O
the	O
only	O
way	O
to	O
share	O
files	O
was	O
by	O
creating	O
a	O
small	O
text	O
file	O
called	O
a	O
"	O
torrent	B-Protocol
"	O
,	O
that	O
they	O
would	O
upload	O
to	O
a	O
torrent	B-Protocol
index	O
site	O
.	O
</s>
<s>
Those	O
who	O
wish	O
to	O
download	O
the	O
file	O
would	O
download	O
the	O
torrent	B-Protocol
,	O
which	O
their	O
client	O
would	O
use	O
to	O
connect	O
to	O
a	O
tracker	B-Protocol
which	O
had	O
a	O
list	O
of	O
the	O
IP	B-Protocol
addresses	I-Protocol
of	O
other	O
seeds	O
and	O
peers	O
in	O
the	O
swarm	O
.	O
</s>
<s>
These	O
files	O
contain	O
metadata	O
about	O
the	O
files	O
to	O
be	O
shared	O
and	O
the	O
trackers	B-Protocol
which	O
keep	O
track	O
of	O
the	O
other	O
seeds	O
and	O
peers	O
.	O
</s>
<s>
In	O
2005	O
,	O
first	O
Vuze	B-Application
and	O
then	O
the	O
BitTorrent	B-Protocol
client	O
introduced	O
distributed	O
tracking	O
using	O
distributed	B-Operating_System
hash	I-Operating_System
tables	I-Operating_System
which	O
allowed	O
clients	O
to	O
exchange	O
data	B-General_Concept
on	O
swarms	O
directly	O
without	O
the	O
need	O
for	O
a	O
torrent	B-Protocol
file	O
.	O
</s>
<s>
In	O
2006	O
,	O
peer	O
exchange	O
functionality	O
was	O
added	O
allowing	O
clients	O
to	O
add	O
peers	O
based	O
on	O
the	O
data	B-General_Concept
found	O
on	O
connected	O
nodes	O
.	O
</s>
<s>
BitTorrent	B-Protocol
v2	O
is	O
intended	O
to	O
work	O
seamlessly	O
with	O
previous	O
versions	O
of	O
the	O
BitTorrent	B-Protocol
protocol	I-Protocol
.	O
</s>
<s>
The	O
main	O
reason	O
for	O
the	O
update	O
was	O
that	O
the	O
old	O
cryptographic	B-Algorithm
hash	I-Algorithm
function	I-Algorithm
,	O
SHA-1	B-Algorithm
is	O
no	O
longer	O
considered	O
safe	O
from	O
malicious	O
attacks	O
by	O
the	O
developers	O
,	O
and	O
as	O
such	O
,	O
v2	O
uses	O
SHA-256	B-Algorithm
.	O
</s>
<s>
To	O
ensure	O
backwards	O
compatibility	O
,	O
the	O
v2	O
.torrent	O
file	O
format	O
supports	O
a	O
hybrid	O
mode	O
where	O
the	O
torrents	B-Protocol
are	O
hashed	O
through	O
both	O
the	O
new	O
method	O
and	O
the	O
old	O
method	O
,	O
with	O
the	O
intent	O
that	O
the	O
files	O
will	O
be	O
shared	O
with	O
peers	O
on	O
both	O
v1	O
and	O
v2	O
swarms	O
.	O
</s>
<s>
Another	O
update	O
to	O
the	O
specification	O
is	O
adding	O
a	O
hash	B-Algorithm
tree	I-Algorithm
to	O
speed	O
up	O
time	O
from	O
adding	O
a	O
torrent	B-Protocol
to	O
downloading	O
files	O
,	O
and	O
to	O
allow	O
more	O
granular	O
checks	O
for	O
file	O
corruption	O
.	O
</s>
<s>
In	O
addition	O
,	O
each	O
file	O
is	O
now	O
hashed	O
individually	O
,	O
enabling	O
files	O
in	O
the	O
swarm	O
to	O
be	O
deduplicated	O
,	O
so	O
that	O
if	O
multiple	O
torrents	B-Protocol
include	O
the	O
same	O
files	O
,	O
but	O
seeders	O
are	O
only	O
seeding	O
the	O
file	O
from	O
some	O
,	O
downloaders	O
of	O
the	O
other	O
torrents	B-Protocol
can	O
still	O
download	O
the	O
file	O
.	O
</s>
<s>
In	O
addition	O
,	O
file	O
hashes	B-Error_Name
can	O
be	O
displayed	O
on	O
tracker	B-Protocol
,	O
torrent	B-Protocol
indexing	O
services	O
,	O
to	O
search	O
for	O
swarms	O
by	O
searching	O
for	O
hashes	B-Error_Name
of	O
files	O
contained	O
in	O
them	O
.	O
</s>
<s>
These	O
hashes	B-Error_Name
are	O
different	O
from	O
the	O
usual	O
SHA-256	B-Algorithm
hash	B-Error_Name
of	O
files	O
and	O
can	O
be	O
obtained	O
using	O
tools	O
.	O
</s>
<s>
Magnet	B-Protocol
links	I-Protocol
for	O
v2	O
also	O
support	O
a	O
hybrid	O
mode	O
to	O
ensure	O
support	O
for	O
legacy	O
clients	O
.	O
</s>
<s>
The	O
BitTorrent	B-Protocol
protocol	I-Protocol
can	O
be	O
used	O
to	O
reduce	O
the	O
server	O
and	O
network	O
impact	O
of	O
distributing	O
large	O
files	O
.	O
</s>
<s>
Rather	O
than	O
downloading	O
a	O
file	O
from	O
a	O
single	O
source	O
server	O
,	O
the	O
BitTorrent	B-Protocol
protocol	I-Protocol
allows	O
users	O
to	O
join	O
a	O
"	O
swarm	O
"	O
of	O
hosts	O
to	O
upload	O
and	O
download	O
from	O
each	O
other	O
simultaneously	O
.	O
</s>
<s>
The	O
protocol	O
is	O
an	O
alternative	O
to	O
the	O
older	O
single	O
source	O
,	O
multiple	O
mirror	O
sources	O
technique	O
for	O
distributing	O
data	B-General_Concept
,	O
and	O
can	O
work	O
effectively	O
over	O
networks	O
with	O
lower	O
bandwidth	O
.	O
</s>
<s>
Using	O
the	O
BitTorrent	B-Protocol
protocol	I-Protocol
,	O
several	O
basic	O
computers	O
,	O
such	O
as	O
home	O
computers	O
,	O
can	O
replace	O
large	O
servers	O
while	O
efficiently	O
distributing	O
files	O
to	O
many	O
recipients	O
.	O
</s>
<s>
This	O
lower	O
bandwidth	O
usage	O
also	O
helps	O
prevent	O
large	O
spikes	O
in	O
internet	O
traffic	O
in	O
a	O
given	O
area	O
,	O
keeping	O
internet	O
speeds	O
higher	O
for	O
all	O
users	O
in	O
general	O
,	O
regardless	O
of	O
whether	O
or	O
not	O
they	O
use	O
the	O
BitTorrent	B-Protocol
protocol	I-Protocol
.	O
</s>
<s>
With	O
BitTorrent	B-Protocol
,	O
the	O
task	O
of	O
distributing	O
the	O
file	O
is	O
shared	O
by	O
those	O
who	O
want	O
it	O
;	O
it	O
is	O
entirely	O
possible	O
for	O
the	O
seed	O
to	O
send	O
only	O
a	O
single	O
copy	O
of	O
the	O
file	O
itself	O
and	O
eventually	O
distribute	O
to	O
an	O
unlimited	O
number	O
of	O
peers	O
.	O
</s>
<s>
Each	O
piece	O
is	O
protected	O
by	O
a	O
cryptographic	B-Algorithm
hash	I-Algorithm
contained	O
in	O
the	O
torrent	B-Protocol
descriptor	O
.	O
</s>
<s>
If	O
a	O
node	O
starts	O
with	O
an	O
authentic	O
copy	O
of	O
the	O
torrent	B-Protocol
descriptor	O
,	O
it	O
can	O
verify	O
the	O
authenticity	O
of	O
the	O
entire	O
file	O
it	O
receives	O
.	O
</s>
<s>
Pieces	O
are	O
typically	O
downloaded	O
non-sequentially	O
,	O
and	O
are	O
rearranged	O
into	O
the	O
correct	O
order	O
by	O
the	O
BitTorrent	B-Protocol
client	O
,	O
which	O
monitors	O
which	O
pieces	O
it	O
needs	O
,	O
and	O
which	O
pieces	O
it	O
has	O
and	O
can	O
upload	O
to	O
other	O
peers	O
.	O
</s>
<s>
Due	O
to	O
the	O
nature	O
of	O
this	O
approach	O
,	O
the	O
download	O
of	O
any	O
file	O
can	O
be	O
halted	O
at	O
any	O
time	O
and	O
be	O
resumed	O
at	O
a	O
later	O
date	O
,	O
without	O
the	O
loss	O
of	O
previously	O
downloaded	O
information	O
,	O
which	O
in	O
turn	O
makes	O
BitTorrent	B-Protocol
particularly	O
useful	O
in	O
the	O
transfer	O
of	O
larger	O
files	O
.	O
</s>
<s>
The	O
distributed	O
nature	O
of	O
BitTorrent	B-Protocol
can	O
lead	O
to	O
a	O
flood-like	B-Protocol
spreading	O
of	O
a	O
file	O
throughout	O
many	O
peer	O
computer	O
nodes	O
.	O
</s>
<s>
Distributed	O
downloading	O
protocols	O
in	O
general	O
provide	O
redundancy	O
against	O
system	O
problems	O
,	O
reduce	O
dependence	O
on	O
the	O
original	O
distributor	O
,	O
and	O
provide	O
sources	O
for	O
the	O
file	O
which	O
are	O
generally	O
transient	B-Device
and	O
therefore	O
there	O
is	O
no	O
single	O
point	O
of	O
failure	O
as	O
in	O
one	O
way	O
server-client	O
transfers	O
.	O
</s>
<s>
Though	O
both	O
ultimately	O
transfer	O
files	O
over	O
a	O
network	O
,	O
a	O
BitTorrent	B-Protocol
download	O
differs	O
from	O
a	O
one	O
way	O
server-client	O
download	O
(	O
as	O
is	O
typical	O
with	O
an	O
HTTP	B-Protocol
or	O
FTP	B-Protocol
request	O
,	O
for	O
example	O
)	O
in	O
several	O
fundamental	O
ways	O
:	O
</s>
<s>
BitTorrent	B-Protocol
makes	O
many	O
small	O
data	B-General_Concept
requests	O
over	O
different	O
IP	B-Protocol
connections	O
to	O
different	O
machines	O
,	O
while	O
server-client	O
downloading	O
is	O
typically	O
made	O
via	O
a	O
single	O
TCP	B-Protocol
connection	O
to	O
a	O
single	O
machine	O
.	O
</s>
<s>
BitTorrent	B-Protocol
downloads	O
in	O
a	O
random	O
or	O
in	O
a	O
"	O
rarest-first	O
"	O
approach	O
that	O
ensures	O
high	O
availability	O
,	O
while	O
classic	O
downloads	O
are	O
sequential	O
.	O
</s>
<s>
Taken	O
together	O
,	O
these	O
differences	O
allow	O
BitTorrent	B-Protocol
to	O
achieve	O
much	O
lower	O
cost	O
to	O
the	O
content	O
provider	O
,	O
much	O
higher	O
redundancy	O
,	O
and	O
much	O
greater	O
resistance	O
to	O
abuse	O
or	O
to	O
"	O
flash	B-General_Concept
crowds	I-General_Concept
"	O
than	O
regular	O
server	B-Application
software	I-Application
.	O
</s>
<s>
However	O
,	O
this	O
protection	O
,	O
theoretically	O
,	O
comes	O
at	O
a	O
cost	O
:	O
downloads	O
can	O
take	O
time	O
to	O
rise	O
to	O
full	O
speed	O
because	O
it	O
may	O
take	O
time	O
for	O
enough	O
peer	O
connections	O
to	O
be	O
established	O
,	O
and	O
it	O
may	O
take	O
time	O
for	O
a	O
node	O
to	O
receive	O
sufficient	O
data	B-General_Concept
to	O
become	O
an	O
effective	O
uploader	O
.	O
</s>
<s>
This	O
contrasts	O
with	O
regular	O
downloads	O
(	O
such	O
as	O
from	O
an	O
HTTP	B-Protocol
server	O
,	O
for	O
example	O
)	O
that	O
,	O
while	O
more	O
vulnerable	O
to	O
overload	O
and	O
abuse	O
,	O
rise	O
to	O
full	O
speed	O
very	O
quickly	O
,	O
and	O
maintain	O
this	O
speed	O
throughout	O
.	O
</s>
<s>
In	O
the	O
beginning	O
,	O
BitTorrent	B-Protocol
's	O
non-contiguous	O
download	O
methods	O
made	O
it	O
harder	O
to	O
support	O
"	O
streaming	O
playback	O
"	O
.	O
</s>
<s>
In	O
2014	O
,	O
the	O
client	O
Popcorn	B-Protocol
Time	I-Protocol
allowed	O
for	O
streaming	O
of	O
BitTorrent	B-Protocol
video	O
files	O
.	O
</s>
<s>
The	O
BitTorrent	B-Protocol
protocol	I-Protocol
provides	O
no	O
way	O
to	O
index	O
torrent	B-Protocol
files	O
.	O
</s>
<s>
As	O
a	O
result	O
,	O
a	O
comparatively	O
small	O
number	O
of	O
websites	O
have	O
hosted	O
a	O
large	O
majority	O
of	O
torrents	B-Protocol
,	O
many	O
linking	O
to	O
copyrighted	O
works	O
without	O
the	O
authorization	O
of	O
copyright	O
holders	O
,	O
rendering	O
those	O
sites	O
especially	O
vulnerable	O
to	O
lawsuits	O
.	O
</s>
<s>
A	O
BitTorrent	B-Protocol
index	O
is	O
a	O
"	O
list	O
of	O
.torrent	O
files	O
,	O
which	O
typically	O
includes	O
descriptions	O
"	O
and	O
information	O
about	O
the	O
torrent	B-Protocol
's	O
content	O
.	O
</s>
<s>
Several	O
types	O
of	O
websites	O
support	O
the	O
discovery	O
and	O
distribution	O
of	O
data	B-General_Concept
on	O
the	O
BitTorrent	B-Protocol
network	O
.	O
</s>
<s>
Public	O
torrent-hosting	O
sites	O
such	O
as	O
The	B-Application
Pirate	I-Application
Bay	I-Application
allow	O
users	O
to	O
search	O
and	O
download	O
from	O
their	O
collection	O
of	O
torrent	B-Protocol
files	O
.	O
</s>
<s>
Users	O
can	O
typically	O
also	O
upload	O
torrent	B-Protocol
files	O
for	O
content	O
they	O
wish	O
to	O
distribute	O
.	O
</s>
<s>
Often	O
,	O
these	O
sites	O
also	O
run	O
BitTorrent	B-Protocol
trackers	I-Protocol
for	O
their	O
hosted	O
torrent	B-Protocol
files	O
,	O
but	O
these	O
two	O
functions	O
are	O
not	O
mutually	O
dependent	O
:	O
a	O
torrent	B-Protocol
file	O
could	O
be	O
hosted	O
on	O
one	O
site	O
and	O
tracked	O
by	O
another	O
unrelated	O
site	O
.	O
</s>
<s>
Private	O
host/tracker	O
sites	O
operate	O
like	O
public	O
ones	O
except	O
that	O
they	O
may	O
restrict	O
access	O
to	O
registered	O
users	O
and	O
may	O
also	O
keep	O
track	O
of	O
the	O
amount	O
of	O
data	B-General_Concept
each	O
user	O
uploads	O
and	O
downloads	O
,	O
in	O
an	O
attempt	O
to	O
reduce	O
"	O
leeching	O
"	O
.	O
</s>
<s>
Web	B-Application
search	I-Application
engines	I-Application
allow	O
the	O
discovery	O
of	O
torrent	B-Protocol
files	O
that	O
are	O
hosted	O
and	O
tracked	O
on	O
other	O
sites	O
;	O
examples	O
include	O
The	B-Application
Pirate	I-Application
Bay	I-Application
and	O
BTDigg	O
.	O
</s>
<s>
These	O
sites	O
allow	O
the	O
user	O
to	O
ask	O
for	O
content	O
meeting	O
specific	O
criteria	O
(	O
such	O
as	O
containing	O
a	O
given	O
word	O
or	O
phrase	O
)	O
and	O
retrieve	O
a	O
list	O
of	O
links	O
to	O
torrent	B-Protocol
files	O
matching	O
those	O
criteria	O
.	O
</s>
<s>
Metasearch	B-Application
engines	I-Application
allow	O
one	O
to	O
search	O
several	O
BitTorrent	B-Protocol
indices	O
and	O
search	B-Application
engines	I-Application
at	O
once	O
.	O
</s>
<s>
The	O
Tribler	B-Language
BitTorrent	B-Protocol
client	O
was	O
among	O
the	O
first	O
to	O
incorporate	O
built-in	O
search	O
capabilities	O
.	O
</s>
<s>
With	O
Tribler	B-Language
,	O
users	O
can	O
find	O
.torrent	O
files	O
held	O
by	O
random	O
peers	O
and	O
taste	O
buddies	O
.	O
</s>
<s>
It	O
adds	O
such	O
an	O
ability	O
to	O
the	O
BitTorrent	B-Protocol
protocol	I-Protocol
using	O
a	O
gossip	B-Operating_System
protocol	I-Operating_System
,	O
somewhat	O
similar	O
to	O
the	O
eXeem	B-Protocol
network	O
which	O
was	O
shut	O
down	O
in	O
2005	O
.	O
</s>
<s>
After	O
a	O
dozen	O
downloads	O
,	O
the	O
Tribler	B-Language
software	O
can	O
roughly	O
estimate	O
the	O
download	O
taste	O
of	O
the	O
user	O
,	O
and	O
recommend	O
additional	O
content	O
.	O
</s>
<s>
A	O
year	O
later	O
,	O
the	O
same	O
team	O
implemented	O
the	O
system	O
as	O
a	O
plugin	O
for	O
Vuze	B-Application
called	O
Cubit	O
and	O
published	O
a	O
follow-up	O
paper	O
reporting	O
its	O
success	O
.	O
</s>
<s>
A	O
somewhat	O
similar	O
facility	O
but	O
with	O
a	O
slightly	O
different	O
approach	O
is	O
provided	O
by	O
the	O
BitComet	B-Protocol
client	O
through	O
its	O
"	O
Torrent	B-Protocol
Exchange	O
"	O
feature	O
.	O
</s>
<s>
Whenever	O
two	O
peers	O
using	O
BitComet	B-Protocol
(	O
with	O
Torrent	B-Protocol
Exchange	O
enabled	O
)	O
connect	O
to	O
each	O
other	O
they	O
exchange	O
lists	O
of	O
all	O
the	O
torrents	B-Protocol
(	O
name	O
and	O
info-hash	O
)	O
they	O
have	O
in	O
the	O
Torrent	B-Protocol
Share	O
storage	O
(	O
torrent	B-Protocol
files	O
which	O
were	O
previously	O
downloaded	O
and	O
for	O
which	O
the	O
user	O
chose	O
to	O
enable	O
sharing	O
by	O
Torrent	B-Protocol
Exchange	O
)	O
.	O
</s>
<s>
Thus	O
each	O
client	O
builds	O
up	O
a	O
list	O
of	O
all	O
the	O
torrents	B-Protocol
shared	O
by	O
the	O
peers	O
it	O
connected	O
to	O
in	O
the	O
current	O
session	O
(	O
or	O
it	O
can	O
even	O
maintain	O
the	O
list	O
between	O
sessions	O
if	O
instructed	O
)	O
.	O
</s>
<s>
At	O
any	O
time	O
the	O
user	O
can	O
search	O
into	O
that	O
Torrent	B-Protocol
Collection	O
list	O
for	O
a	O
certain	O
torrent	B-Protocol
and	O
sort	O
the	O
list	O
by	O
categories	O
.	O
</s>
<s>
When	O
the	O
user	O
chooses	O
to	O
download	O
a	O
torrent	B-Protocol
from	O
that	O
list	O
,	O
the	O
.torrent	O
file	O
is	O
automatically	O
searched	O
for	O
(	O
by	O
info-hash	O
value	O
)	O
in	O
the	O
DHT	B-Operating_System
Network	I-Operating_System
and	O
when	O
found	O
it	O
is	O
downloaded	O
by	O
the	O
querying	O
client	O
which	O
can	O
after	O
that	O
create	O
and	O
initiate	O
a	O
downloading	O
task	O
.	O
</s>
<s>
Users	O
find	O
a	O
torrent	B-Protocol
of	O
interest	O
on	O
a	O
torrent	B-Protocol
index	O
site	O
or	O
by	O
using	O
a	O
search	B-Application
engine	I-Application
built	O
into	O
the	O
client	O
,	O
download	O
it	O
,	O
and	O
open	O
it	O
with	O
a	O
BitTorrent	B-Protocol
client	O
.	O
</s>
<s>
The	O
client	O
connects	O
to	O
the	O
tracker(s )	O
or	O
seeds	O
specified	O
in	O
the	O
torrent	B-Protocol
file	O
,	O
from	O
which	O
it	O
receives	O
a	O
list	O
of	O
seeds	O
and	O
peers	O
currently	O
transferring	O
pieces	O
of	O
the	O
file(s )	O
.	O
</s>
<s>
The	O
effectiveness	O
of	O
this	O
data	B-General_Concept
exchange	O
depends	O
largely	O
on	O
the	O
policies	O
that	O
clients	O
use	O
to	O
determine	O
to	O
whom	O
to	O
send	O
data	B-General_Concept
.	O
</s>
<s>
Clients	O
may	O
prefer	O
to	O
send	O
data	B-General_Concept
to	O
peers	O
that	O
send	O
data	B-General_Concept
back	O
to	O
them	O
(	O
a	O
"	O
tit	O
for	O
tat	O
"	O
exchange	O
scheme	O
)	O
,	O
which	O
encourages	O
fair	O
trading	O
.	O
</s>
<s>
But	O
strict	O
policies	O
often	O
result	O
in	O
suboptimal	O
situations	O
,	O
such	O
as	O
when	O
newly	O
joined	O
peers	O
are	O
unable	O
to	O
receive	O
any	O
data	B-General_Concept
because	O
they	O
do	O
not	O
have	O
any	O
pieces	O
yet	O
to	O
trade	O
themselves	O
or	O
when	O
two	O
peers	O
with	O
a	O
good	O
connection	O
between	O
them	O
do	O
not	O
exchange	O
data	B-General_Concept
simply	O
because	O
neither	O
of	O
them	O
takes	O
the	O
initiative	O
.	O
</s>
<s>
To	O
counter	O
these	O
effects	O
,	O
the	O
official	O
BitTorrent	B-Protocol
client	O
program	O
uses	O
a	O
mechanism	O
called	O
"	O
optimistic	O
unchoking	O
"	O
,	O
whereby	O
the	O
client	O
reserves	O
a	O
portion	O
of	O
its	O
available	O
bandwidth	O
for	O
sending	O
pieces	O
to	O
random	O
peers	O
(	O
not	O
necessarily	O
known	O
good	O
partners	O
,	O
so	O
called	O
preferred	O
peers	O
)	O
in	O
hopes	O
of	O
discovering	O
even	O
better	O
partners	O
and	O
to	O
ensure	O
that	O
newcomers	O
get	O
a	O
chance	O
to	O
join	O
the	O
swarm	O
.	O
</s>
<s>
Although	O
"	O
swarming	O
"	O
scales	O
well	O
to	O
tolerate	O
"	O
flash	B-General_Concept
crowds	I-General_Concept
"	O
for	O
popular	O
content	O
,	O
it	O
is	O
less	O
useful	O
for	O
unpopular	O
or	O
niche	O
market	O
content	O
.	O
</s>
<s>
Since	O
maintaining	O
seeds	O
for	O
unpopular	O
content	O
entails	O
high	O
bandwidth	O
and	O
administrative	O
costs	O
,	O
this	O
runs	O
counter	O
to	O
the	O
goals	O
of	O
publishers	O
that	O
value	O
BitTorrent	B-Protocol
as	O
a	O
cheap	O
alternative	O
to	O
a	O
client-server	O
approach	O
.	O
</s>
<s>
This	O
occurs	O
on	O
a	O
huge	O
scale	O
;	O
measurements	O
have	O
shown	O
that	O
38%	O
of	O
all	O
new	O
torrents	B-Protocol
become	O
unavailable	O
within	O
the	O
first	O
month	O
.	O
</s>
<s>
More	O
sophisticated	O
solutions	O
have	O
also	O
been	O
proposed	O
;	O
generally	O
,	O
these	O
use	O
cross-torrent	O
mechanisms	O
through	O
which	O
multiple	O
torrents	B-Protocol
can	O
cooperate	O
to	O
better	O
share	O
content	O
.	O
</s>
<s>
The	O
peer	O
distributing	O
a	O
data	B-General_Concept
file	O
treats	O
the	O
file	O
as	O
a	O
number	O
of	O
identically	O
sized	O
pieces	O
,	O
usually	O
with	O
byte	O
sizes	O
of	O
a	O
power	O
of	O
2	O
,	O
and	O
typically	O
between	O
32kB	O
and	O
16MB	O
each	O
.	O
</s>
<s>
The	O
peer	O
creates	O
a	O
hash	B-Error_Name
for	O
each	O
piece	O
,	O
using	O
the	O
SHA-1	B-Algorithm
hash	I-Algorithm
function	O
,	O
and	O
records	O
it	O
in	O
the	O
torrent	B-Protocol
file	O
.	O
</s>
<s>
Pieces	O
with	O
sizes	O
greater	O
than	O
512kB	O
will	O
reduce	O
the	O
size	O
of	O
a	O
torrent	B-Protocol
file	O
for	O
a	O
very	O
large	O
payload	O
,	O
but	O
is	O
claimed	O
to	O
reduce	O
the	O
efficiency	O
of	O
the	O
protocol	O
.	O
</s>
<s>
When	O
another	O
peer	O
later	O
receives	O
a	O
particular	O
piece	O
,	O
the	O
hash	B-Error_Name
of	O
the	O
piece	O
is	O
compared	O
to	O
the	O
recorded	O
hash	B-Error_Name
to	O
test	O
that	O
the	O
piece	O
is	O
error-free	O
.	O
</s>
<s>
The	O
exact	O
information	O
contained	O
in	O
the	O
torrent	B-Protocol
file	O
depends	O
on	O
the	O
version	O
of	O
the	O
BitTorrent	B-Protocol
protocol	I-Protocol
.	O
</s>
<s>
By	O
convention	O
,	O
the	O
name	O
of	O
a	O
torrent	B-Protocol
file	O
has	O
the	O
suffix	O
.torrent	O
.	O
</s>
<s>
Torrent	B-Protocol
files	O
use	O
the	O
Bencode	B-Protocol
file	O
format	O
,	O
and	O
contain	O
an	O
"	O
announce	O
"	O
section	O
,	O
which	O
specifies	O
the	O
URL	O
of	O
the	O
tracker	B-Protocol
,	O
and	O
an	O
"	O
info	O
"	O
section	O
,	O
containing	O
(	O
suggested	O
)	O
names	O
for	O
the	O
files	O
,	O
their	O
lengths	O
,	O
the	O
piece	O
length	O
used	O
,	O
and	O
a	O
SHA-1	B-Algorithm
hash	I-Algorithm
code	O
for	O
each	O
piece	O
,	O
all	O
of	O
which	O
are	O
used	O
by	O
clients	O
to	O
verify	O
the	O
integrity	O
of	O
the	O
data	B-General_Concept
they	O
receive	O
.	O
</s>
<s>
Though	O
SHA-1	B-Algorithm
has	O
shown	O
signs	O
of	O
cryptographic	O
weakness	O
,	O
Bram	O
Cohen	O
did	O
not	O
initially	O
consider	O
the	O
risk	O
big	O
enough	O
for	O
a	O
backward	O
incompatible	O
change	O
to	O
,	O
for	O
example	O
,	O
SHA-3	B-Algorithm
.	O
</s>
<s>
As	O
of	O
BitTorrent	B-Protocol
v2	O
the	O
hash	B-Error_Name
function	I-Error_Name
has	O
been	O
updated	O
to	O
SHA-256	B-Algorithm
.	O
</s>
<s>
In	O
the	O
early	O
days	O
,	O
torrent	B-Protocol
files	O
were	O
typically	O
published	O
to	O
torrent	B-Protocol
index	O
websites	O
,	O
and	O
registered	O
with	O
at	O
least	O
one	O
tracker	B-Protocol
.	O
</s>
<s>
The	O
tracker	B-Protocol
maintained	O
lists	O
of	O
the	O
clients	O
currently	O
connected	O
to	O
the	O
swarm	O
.	O
</s>
<s>
Alternatively	O
,	O
in	O
a	O
trackerless	O
system	O
(	O
decentralized	O
tracking	O
)	O
every	O
peer	O
acts	O
as	O
a	O
tracker	B-Protocol
.	O
</s>
<s>
Azureus	B-Application
was	O
the	O
first	O
BitTorrent	B-Protocol
client	O
to	O
implement	O
such	O
a	O
system	O
through	O
the	O
distributed	B-Operating_System
hash	I-Operating_System
table	I-Operating_System
(	O
DHT	B-Operating_System
)	O
method	O
.	O
</s>
<s>
An	O
alternative	O
and	O
incompatible	O
DHT	B-Operating_System
system	O
,	O
known	O
as	O
Mainline	B-Protocol
DHT	I-Protocol
,	O
was	O
released	O
in	O
the	O
Mainline	B-Protocol
BitTorrent	I-Protocol
client	O
three	O
weeks	O
later	O
(	O
though	O
it	O
had	O
been	O
in	O
development	O
since	O
2002	O
)	O
and	O
subsequently	O
adopted	O
by	O
the	O
μTorrent	B-Application
,	O
Transmission	B-Language
,	O
rTorrent	B-Language
,	O
KTorrent	B-Language
,	O
BitComet	B-Protocol
,	O
and	O
Deluge	B-Language
clients	O
.	O
</s>
<s>
After	O
the	O
DHT	B-Operating_System
was	O
adopted	O
,	O
a	O
"	O
private	O
"	O
flag	O
–	O
analogous	O
to	O
the	O
broadcast	B-Device
flag	I-Device
–	O
was	O
unofficially	O
introduced	O
,	O
telling	O
clients	O
to	O
restrict	O
the	O
use	O
of	O
decentralized	O
tracking	O
regardless	O
of	O
the	O
user	O
's	O
desires	O
.	O
</s>
<s>
The	O
flag	O
is	O
intentionally	O
placed	O
in	O
the	O
info	O
section	O
of	O
the	O
torrent	B-Protocol
so	O
that	O
it	O
cannot	O
be	O
disabled	O
or	O
removed	O
without	O
changing	O
the	O
identity	O
of	O
the	O
torrent	B-Protocol
.	O
</s>
<s>
The	O
purpose	O
of	O
the	O
flag	O
is	O
to	O
prevent	O
torrents	B-Protocol
from	O
being	O
shared	O
with	O
clients	O
that	O
do	O
not	O
have	O
access	O
to	O
the	O
tracker	B-Protocol
.	O
</s>
<s>
Clients	O
that	O
have	O
ignored	O
the	O
private	O
flag	O
were	O
banned	O
by	O
many	O
trackers	B-Protocol
,	O
discouraging	O
the	O
practice	O
.	O
</s>
<s>
BitTorrent	B-Protocol
does	O
not	O
,	O
on	O
its	O
own	O
,	O
offer	O
its	O
users	O
anonymity	O
.	O
</s>
<s>
One	O
can	O
usually	O
see	O
the	O
IP	B-Protocol
addresses	I-Protocol
of	O
all	O
peers	O
in	O
a	O
swarm	O
in	O
one	O
's	O
own	O
client	O
or	O
firewall	O
program	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
BitTorrent	B-Protocol
client	O
Tribler	B-Language
makes	O
available	O
a	O
Tor-like	O
onion	B-Protocol
network	I-Protocol
,	O
optionally	O
routing	O
transfers	O
through	O
other	O
peers	O
to	O
obscure	O
which	O
client	O
has	O
requested	O
the	O
data	B-General_Concept
.	O
</s>
<s>
The	O
exit	B-Application
node	I-Application
would	O
be	O
visible	O
to	O
peers	O
in	O
a	O
swarm	O
,	O
but	O
the	O
Tribler	B-Language
organization	O
provides	O
exit	B-Application
nodes	I-Application
.	O
</s>
<s>
One	O
advantage	O
of	O
Tribler	B-Language
is	O
that	O
clearnet	O
torrents	B-Protocol
can	O
be	O
downloaded	O
with	O
only	O
a	O
small	O
decrease	O
in	O
download	O
speed	O
from	O
one	O
"	O
hop	O
"	O
of	O
routing	O
.	O
</s>
<s>
i2p	B-Protocol
provides	O
a	O
similar	O
anonymity	O
layer	O
although	O
in	O
that	O
case	O
,	O
one	O
can	O
only	O
download	O
torrents	B-Protocol
that	O
have	O
been	O
uploaded	O
to	O
the	O
i2p	B-Protocol
network	O
.	O
</s>
<s>
The	O
bittorrent	B-Protocol
client	O
Vuze	B-Application
allows	O
users	O
who	O
are	O
not	O
concerned	O
about	O
anonymity	O
to	O
take	O
clearnet	O
torrents	B-Protocol
,	O
and	O
make	O
them	O
available	O
on	O
the	O
i2p	B-Protocol
network	O
.	O
</s>
<s>
Most	O
BitTorrent	B-Protocol
clients	O
are	O
not	O
designed	O
to	O
provide	O
anonymity	O
when	O
used	O
over	O
Tor	B-Application
,	O
and	O
there	O
is	O
some	O
debate	O
as	O
to	O
whether	O
torrenting	B-Protocol
over	O
Tor	B-Application
acts	O
as	O
a	O
drag	O
on	O
the	O
network	O
.	O
</s>
<s>
Private	O
torrent	B-Protocol
trackers	I-Protocol
are	O
usually	O
invitation	O
only	O
,	O
and	O
require	O
members	O
to	O
participate	O
in	O
uploading	O
,	O
but	O
have	O
the	O
downside	O
of	O
a	O
single	O
centralized	O
point	O
of	O
failure	O
.	O
</s>
<s>
Oink	O
's	O
Pink	O
Palace	O
and	O
What.cd	O
are	O
examples	O
of	O
private	O
trackers	B-Protocol
which	O
have	O
been	O
shut	O
down	O
.	O
</s>
<s>
Seedbox	O
services	O
download	O
the	O
torrent	B-Protocol
files	O
first	O
to	O
the	O
company	O
's	O
servers	O
,	O
allowing	O
the	O
user	O
to	O
direct	O
download	O
the	O
file	O
from	O
there	O
.	O
</s>
<s>
One	O
's	O
IP	B-Protocol
address	I-Protocol
would	O
be	O
visible	O
to	O
the	O
Seedbox	O
provider	O
,	O
but	O
not	O
to	O
third	O
parties	O
.	O
</s>
<s>
Virtual	B-Application
private	I-Application
networks	I-Application
encrypt	O
transfers	O
,	O
and	O
substitute	O
a	O
different	O
IP	B-Protocol
address	I-Protocol
for	O
the	O
user	O
's	O
,	O
so	O
that	O
anyone	O
monitoring	O
a	O
torrent	B-Protocol
swarm	O
will	O
only	O
see	O
that	O
address	O
.	O
</s>
<s>
On	O
2	O
May	O
2005	O
,	O
Azureus	B-Application
2.3.0.0	O
(	O
now	O
known	O
as	O
Vuze	B-Application
)	O
was	O
released	O
,	O
introducing	O
support	O
for	O
"	O
trackerless	O
"	O
torrents	B-Protocol
through	O
a	O
system	O
called	O
the	O
"	O
distributed	O
database	O
"	O
.	O
</s>
<s>
This	O
system	O
is	O
a	O
distributed	B-Operating_System
hash	I-Operating_System
table	I-Operating_System
implementation	O
which	O
allows	O
the	O
client	O
to	O
use	O
torrents	B-Protocol
that	O
do	O
not	O
have	O
a	O
working	O
BitTorrent	B-Protocol
tracker	I-Protocol
.	O
</s>
<s>
Instead	O
just	O
bootstrapping	O
server	O
is	O
used	O
(	O
router.bittorrent.com,	O
dht.transmissionbt.com	O
or	O
router.utorrent.com	O
)	O
.	O
</s>
<s>
The	O
following	O
month	O
,	O
BitTorrent	B-Protocol
,	O
Inc	O
.	O
released	O
version	O
4.2.0	O
of	O
the	O
Mainline	B-Protocol
BitTorrent	I-Protocol
client	O
,	O
which	O
supported	O
an	O
alternative	O
DHT	B-Operating_System
implementation	O
(	O
popularly	O
known	O
as	O
"	O
Mainline	B-Protocol
DHT	I-Protocol
"	O
,	O
outlined	O
in	O
a	O
draft	O
on	O
their	O
website	O
)	O
that	O
is	O
incompatible	O
with	O
that	O
of	O
Azureus	B-Application
.	O
</s>
<s>
In	O
2014	O
,	O
measurement	O
showed	O
concurrent	O
users	O
of	O
Mainline	B-Protocol
DHT	I-Protocol
to	O
be	O
from	O
10	O
million	O
to	O
25million	O
,	O
with	O
a	O
daily	O
churn	O
of	O
at	O
least	O
10million	O
.	O
</s>
<s>
Current	O
versions	O
of	O
the	O
official	O
BitTorrent	B-Protocol
client	O
,	O
μTorrent	B-Application
,	O
BitComet	B-Protocol
,	O
Transmission	B-Language
and	O
BitSpirit	O
all	O
share	O
compatibility	O
with	O
Mainline	B-Protocol
DHT	I-Protocol
.	O
</s>
<s>
Both	O
DHT	B-Operating_System
implementations	O
are	O
based	O
on	O
Kademlia	B-Operating_System
.	O
</s>
<s>
As	O
of	O
version	O
3.0.5.0	O
,	O
Azureus	B-Application
also	O
supports	O
Mainline	B-Protocol
DHT	I-Protocol
in	O
addition	O
to	O
its	O
own	O
distributed	O
database	O
through	O
use	O
of	O
an	O
optional	O
application	O
plugin	O
.	O
</s>
<s>
This	O
potentially	O
allows	O
the	O
Azureus/Vuze	O
client	O
to	O
reach	O
a	O
bigger	O
swarm	O
.	O
</s>
<s>
Another	O
idea	O
that	O
has	O
surfaced	O
in	O
Vuze	B-Application
is	O
that	O
of	O
virtual	O
torrents	B-Protocol
.	O
</s>
<s>
This	O
idea	O
is	O
based	O
on	O
the	O
distributed	O
tracker	B-Protocol
approach	O
and	O
is	O
used	O
to	O
describe	O
some	O
web	O
resource	O
.	O
</s>
<s>
Currently	O
,	O
it	O
is	O
used	O
for	O
instant	B-Application
messaging	I-Application
.	O
</s>
<s>
Anatomic	O
P2P	O
is	O
another	O
approach	O
,	O
which	O
uses	O
a	O
decentralized	O
network	O
of	O
nodes	O
that	O
route	O
traffic	O
to	O
dynamic	O
trackers	B-Protocol
.	O
</s>
<s>
Most	O
BitTorrent	B-Protocol
clients	O
also	O
use	O
peer	O
exchange	O
(	O
PEX	O
)	O
to	O
gather	O
peers	O
in	O
addition	O
to	O
trackers	B-Protocol
and	O
DHT	B-Operating_System
.	O
</s>
<s>
With	O
the	O
3.0.5.0	O
release	O
of	O
Vuze	B-Application
,	O
all	O
major	O
BitTorrent	B-Protocol
clients	O
now	O
have	O
compatible	O
peer	O
exchange	O
.	O
</s>
<s>
Web	O
"	O
seeding	O
"	O
was	O
implemented	O
in	O
2006	O
as	O
the	O
ability	O
of	O
BitTorrent	B-Protocol
clients	O
to	O
download	O
torrent	B-Protocol
pieces	O
from	O
an	O
HTTP	B-Protocol
source	O
in	O
addition	O
to	O
the	O
"	O
swarm	O
"	O
.	O
</s>
<s>
The	O
advantage	O
of	O
this	O
feature	O
is	O
that	O
a	O
website	O
may	O
distribute	O
a	O
torrent	B-Protocol
for	O
a	O
particular	O
file	O
or	O
batch	O
of	O
files	O
and	O
make	O
those	O
files	O
available	O
for	O
download	O
from	O
that	O
same	O
web	O
server	O
;	O
this	O
can	O
simplify	O
long-term	O
seeding	O
and	O
load	B-Application
balancing	I-Application
through	O
the	O
use	O
of	O
existing	O
,	O
cheap	O
,	O
web	O
hosting	O
setups	O
.	O
</s>
<s>
In	O
theory	O
,	O
this	O
would	O
make	O
using	O
BitTorrent	B-Protocol
almost	O
as	O
easy	O
for	O
a	O
web	O
publisher	O
as	O
creating	O
a	O
direct	O
HTTP	B-Protocol
download	O
.	O
</s>
<s>
This	O
feature	O
has	O
two	O
distinct	O
specifications	O
,	O
both	O
of	O
which	O
are	O
supported	O
by	O
Libtorrent	B-Language
and	O
the	O
26+	O
clients	O
that	O
use	O
it	O
.	O
</s>
<s>
This	O
first	O
specification	O
requires	O
running	O
a	O
web	O
service	O
that	O
serves	O
content	O
by	O
info-hash	O
and	O
piece	O
number	O
,	O
rather	O
than	O
filename	O
.	O
</s>
<s>
The	O
other	O
specification	O
is	O
created	O
by	O
GetRight	B-Protocol
authors	O
and	O
can	O
rely	O
on	O
a	O
basic	O
HTTP	B-Protocol
download	O
space	O
(	O
using	O
byte	B-Protocol
serving	I-Protocol
)	O
.	O
</s>
<s>
In	O
September	O
2010	O
,	O
a	O
new	O
service	O
named	O
Burnbit	O
was	O
launched	O
which	O
generates	O
a	O
torrent	B-Protocol
from	O
any	O
URL	O
using	O
webseeding	O
.	O
</s>
<s>
There	O
are	O
server-side	O
solutions	O
that	O
provide	O
initial	O
seeding	O
of	O
the	O
file	O
from	O
the	O
web	O
server	O
via	O
standard	O
BitTorrent	B-Protocol
protocol	I-Protocol
and	O
when	O
the	O
number	O
of	O
external	O
seeders	O
reach	O
a	O
limit	O
,	O
they	O
stop	O
serving	O
the	O
file	O
from	O
the	O
original	O
source	O
.	O
</s>
<s>
A	O
technique	O
called	O
broadcatching	O
combines	O
RSS	O
feeds	O
with	O
the	O
BitTorrent	B-Protocol
protocol	I-Protocol
to	O
create	O
a	O
content	O
delivery	O
system	O
,	O
further	O
simplifying	O
and	O
automating	O
content	O
distribution	O
.	O
</s>
<s>
In	O
an	O
article	O
entitled	O
Broadcatching	O
with	O
BitTorrent	B-Protocol
,	O
Scott	O
Raymond	O
explained	O
:	O
</s>
<s>
The	O
RSS	O
feed	O
will	O
track	O
the	O
content	O
,	O
while	O
BitTorrent	B-Protocol
ensures	O
content	O
integrity	O
with	O
cryptographic	B-Algorithm
hashing	I-Algorithm
of	O
all	O
data	B-General_Concept
,	O
so	O
feed	O
subscribers	O
will	O
receive	O
uncorrupted	O
content	O
.	O
</s>
<s>
One	O
of	O
the	O
first	O
and	O
popular	O
software	O
clients	O
(	O
free	B-Application
and	O
open	B-Application
source	I-Application
)	O
for	O
broadcatching	O
is	O
Miro	B-Language
.	O
</s>
<s>
Other	O
free	B-Application
software	I-Application
clients	O
such	O
as	O
PenguinTV	O
and	O
KatchTV	O
are	O
also	O
now	O
supporting	O
broadcatching	O
.	O
</s>
<s>
The	O
BitTorrent	B-Protocol
web-service	O
MoveDigital	O
added	O
the	O
ability	O
to	O
make	O
torrents	B-Protocol
available	O
to	O
any	O
web	O
application	O
capable	O
of	O
parsing	O
XML	B-Protocol
through	O
its	O
standard	O
REST-based	O
interface	O
in	O
2006	O
,	O
though	O
this	O
has	O
since	O
been	O
discontinued	O
.	O
</s>
<s>
Additionally	O
,	O
Torrenthut	O
is	O
developing	O
a	O
similar	O
torrent	B-Protocol
API	B-General_Concept
that	O
will	O
provide	O
the	O
same	O
features	O
,	O
and	O
help	O
bring	O
the	O
torrent	B-Protocol
community	O
to	O
Web	O
2.0	O
standards	O
.	O
</s>
<s>
Alongside	O
this	O
release	O
is	O
a	O
first	O
PHP	B-Application
application	O
built	O
using	O
the	O
API	B-General_Concept
called	O
PEP	O
,	O
which	O
will	O
parse	O
any	O
Really	O
Simple	O
Syndication	O
(	O
RSS	O
2.0	O
)	O
feed	O
and	O
automatically	O
create	O
and	O
seed	O
a	O
torrent	B-Protocol
for	O
each	O
enclosure	O
found	O
in	O
that	O
feed	O
.	O
</s>
<s>
Since	O
BitTorrent	B-Protocol
makes	O
up	O
a	O
large	O
proportion	O
of	O
total	O
traffic	O
,	O
some	O
ISPs	O
have	O
chosen	O
to	O
"	O
throttle	O
"	O
(	O
slow	O
down	O
)	O
BitTorrent	B-Protocol
transfers	O
.	O
</s>
<s>
For	O
this	O
reason	O
,	O
methods	O
have	O
been	O
developed	O
to	O
disguise	O
BitTorrent	B-Protocol
traffic	O
in	O
an	O
attempt	O
to	O
thwart	O
these	O
efforts	O
.	O
</s>
<s>
Protocol	B-Protocol
header	I-Protocol
encrypt	I-Protocol
(	O
PHE	O
)	O
and	O
Message	O
stream	O
encryption/Protocol	O
encryption	O
(	O
MSE/PE	B-Protocol
)	O
are	O
features	O
of	O
some	O
BitTorrent	B-Protocol
clients	O
that	O
attempt	O
to	O
make	O
BitTorrent	B-Protocol
hard	O
to	O
detect	O
and	O
throttle	O
.	O
</s>
<s>
As	O
of	O
November	O
2015	O
,	O
Vuze	B-Application
,	O
BitComet	B-Protocol
,	O
KTorrent	B-Language
,	O
Transmission	B-Language
,	O
Deluge	B-Language
,	O
μTorrent	B-Application
,	O
MooPolice	O
,	O
Halite	O
,	O
qBittorrent	B-Application
,	O
rTorrent	B-Language
,	O
and	O
the	O
latest	O
official	O
BitTorrent	B-Protocol
client	O
(	O
v6	O
)	O
support	O
MSE/PE	B-Protocol
encryption	O
.	O
</s>
<s>
In	O
August	O
2007	O
,	O
Comcast	O
was	O
preventing	O
BitTorrent	B-Protocol
seeding	O
by	O
monitoring	O
and	O
interfering	O
with	O
the	O
communication	O
between	O
peers	O
.	O
</s>
<s>
Protection	O
against	O
these	O
efforts	O
is	O
provided	O
by	O
proxying	B-Application
the	O
client-tracker	O
traffic	O
via	O
an	O
encrypted	B-Protocol
tunnel	I-Protocol
to	O
a	O
point	O
outside	O
of	O
the	O
Comcast	O
network	O
.	O
</s>
<s>
In	O
2008	O
,	O
Comcast	O
called	O
a	O
"	O
truce	O
"	O
with	O
BitTorrent	B-Protocol
,	O
Inc	O
.	O
with	O
the	O
intention	O
of	O
shaping	O
traffic	O
in	O
a	O
protocol-agnostic	O
manner	O
.	O
</s>
<s>
In	O
general	O
,	O
although	O
encryption	O
can	O
make	O
it	O
difficult	O
to	O
determine	O
what	O
is	O
being	O
shared	O
,	O
BitTorrent	B-Protocol
is	O
vulnerable	O
to	O
traffic	O
analysis	O
.	O
</s>
<s>
Thus	O
,	O
even	O
with	O
MSE/PE	B-Protocol
,	O
it	O
may	O
be	O
possible	O
for	O
an	O
ISP	O
to	O
recognize	O
BitTorrent	B-Protocol
and	O
also	O
to	O
determine	O
that	O
a	O
system	O
is	O
no	O
longer	O
downloading	O
but	O
only	O
uploading	O
data	B-General_Concept
,	O
and	O
terminate	O
its	O
connection	O
by	O
injecting	O
TCP	B-Protocol
RST	O
(	O
reset	O
flag	O
)	O
packets	O
.	O
</s>
<s>
Another	O
unofficial	O
feature	O
is	O
an	O
extension	B-Protocol
to	O
the	O
BitTorrent	B-Protocol
metadata	O
format	O
proposed	O
by	O
John	O
Hoffman	O
and	O
implemented	O
by	O
several	O
indexing	O
websites	O
.	O
</s>
<s>
It	O
allows	O
the	O
use	O
of	O
multiple	O
trackers	B-Protocol
per	O
file	O
,	O
so	O
if	O
one	O
tracker	B-Protocol
fails	O
,	O
others	O
can	O
continue	O
to	O
support	O
file	O
transfer	O
.	O
</s>
<s>
It	O
is	O
implemented	O
in	O
several	O
clients	O
,	O
such	O
as	O
BitComet	B-Protocol
,	O
BitTornado	O
,	O
BitTorrent	B-Protocol
,	O
KTorrent	B-Language
,	O
Transmission	B-Language
,	O
Deluge	B-Language
,	O
μTorrent	B-Application
,	O
rtorrent	B-Language
,	O
Vuze	B-Application
,	O
and	O
Frostwire	B-Protocol
.	O
</s>
<s>
Trackers	B-Protocol
are	O
placed	O
in	O
groups	O
,	O
or	O
tiers	O
,	O
with	O
a	O
tracker	B-Protocol
randomly	O
chosen	O
from	O
the	O
top	O
tier	O
and	O
tried	O
,	O
moving	O
to	O
the	O
next	O
tier	O
if	O
all	O
the	O
trackers	B-Protocol
in	O
the	O
top	O
tier	O
fail	O
.	O
</s>
<s>
Torrents	B-Protocol
with	O
multiple	O
trackers	B-Protocol
can	O
decrease	O
the	O
time	O
it	O
takes	O
to	O
download	O
a	O
file	O
,	O
but	O
also	O
have	O
a	O
few	O
consequences	O
:	O
</s>
<s>
Poorly	O
implemented	O
clients	O
may	O
contact	O
multiple	O
trackers	B-Protocol
,	O
leading	O
to	O
more	O
overhead-traffic	O
.	O
</s>
<s>
Torrents	B-Protocol
from	O
closed	O
trackers	B-Protocol
suddenly	O
become	O
downloadable	O
by	O
non-members	O
,	O
as	O
they	O
can	O
connect	O
to	O
a	O
seed	O
via	O
an	O
open	O
tracker	B-Protocol
.	O
</s>
<s>
BitTorrent	B-Protocol
,	O
Inc	O
.	O
was	O
working	O
with	O
Oversi	O
on	O
new	O
Policy	O
Discover	O
Protocols	O
that	O
query	O
the	O
ISP	O
for	O
capabilities	O
and	O
network	O
architecture	O
information	O
.	O
</s>
<s>
The	O
BitTorrent	B-Protocol
specification	O
is	O
free	B-Application
to	O
use	O
and	O
many	O
clients	O
are	O
open	B-Application
source	I-Application
,	O
so	O
BitTorrent	B-Protocol
clients	O
have	O
been	O
created	O
for	O
all	O
common	O
operating	B-General_Concept
systems	I-General_Concept
using	O
a	O
variety	O
of	O
programming	O
languages	O
.	O
</s>
<s>
The	O
official	O
BitTorrent	B-Protocol
client	O
,	O
μTorrent	B-Application
,	O
qBittorrent	B-Application
,	O
Transmission	B-Language
,	O
Vuze	B-Application
,	O
and	O
BitComet	B-Protocol
are	O
some	O
of	O
the	O
most	O
popular	O
clients	O
.	O
</s>
<s>
Some	O
BitTorrent	B-Protocol
implementations	O
such	O
as	O
MLDonkey	B-Protocol
and	O
Torrentflux	O
are	O
designed	O
to	O
run	O
as	O
servers	O
.	O
</s>
<s>
Server-oriented	O
BitTorrent	B-Protocol
implementations	O
can	O
also	O
be	O
hosted	O
by	O
hosting	O
providers	O
at	O
co-located	B-Application
facilities	O
with	O
high	O
bandwidth	O
Internet	O
connectivity	O
(	O
e.g.	O
,	O
a	O
datacenter	O
)	O
which	O
can	O
provide	O
dramatic	O
speed	O
benefits	O
over	O
using	O
BitTorrent	B-Protocol
from	O
a	O
regular	O
home	O
broadband	O
connection	O
.	O
</s>
<s>
Services	O
such	O
as	O
ImageShack	O
can	O
download	O
files	O
on	O
BitTorrent	B-Protocol
for	O
the	O
user	O
,	O
allowing	O
them	O
to	O
download	O
the	O
entire	O
file	O
by	O
HTTP	B-Protocol
once	O
it	O
is	O
finished	O
.	O
</s>
<s>
The	O
Opera	B-Application
web	I-Application
browser	I-Application
supports	O
BitTorrent	B-Protocol
natively	O
.	O
</s>
<s>
Brave	B-Application
web	B-Application
browser	I-Application
ships	O
with	O
an	O
extension	B-Protocol
which	O
supports	O
WebTorrent	B-Protocol
,	O
a	O
BitTorrent-like	O
protocol	O
based	O
on	O
WebRTC	B-Protocol
instead	O
of	O
UDP	B-Protocol
and	O
TCP	B-Protocol
.	O
</s>
<s>
BitLet	O
allowed	O
users	O
to	O
download	O
Torrents	B-Protocol
directly	O
from	O
their	O
browser	B-Application
using	O
a	O
Java	B-Application
applet	I-Application
(	O
until	O
browsers	B-Application
removed	O
support	O
for	O
Java	B-Application
applets	I-Application
)	O
.	O
</s>
<s>
An	O
increasing	O
number	O
of	O
hardware	O
devices	O
are	O
being	O
made	O
to	O
support	O
BitTorrent	B-Protocol
.	O
</s>
<s>
These	O
include	O
routers	O
and	O
NAS	O
devices	O
containing	O
BitTorrent-capable	O
firmware	O
like	O
OpenWrt	B-Application
.	O
</s>
<s>
Proprietary	O
versions	O
of	O
the	O
protocol	O
which	O
implement	O
DRM	O
,	O
encryption	O
,	O
and	O
authentication	O
are	O
found	O
within	O
managed	O
clients	O
such	O
as	O
Pando	B-Protocol
.	O
</s>
<s>
A	O
growing	O
number	O
of	O
individuals	O
and	O
organizations	O
are	O
using	O
BitTorrent	B-Protocol
to	O
distribute	O
their	O
own	O
or	O
licensed	O
works	O
(	O
e.g.	O
</s>
<s>
indie	O
bands	O
distributing	O
digital	B-Operating_System
files	I-Operating_System
of	O
their	O
new	O
songs	O
)	O
.	O
</s>
<s>
Independent	O
adopters	O
report	O
that	O
BitTorrent	B-Protocol
technology	O
reduces	O
demands	O
on	O
private	O
networking	O
hardware	O
and	O
bandwidth	O
,	O
an	O
essential	O
for	O
non-profit	O
groups	O
with	O
large	O
amounts	O
of	O
internet	O
traffic	O
.	O
</s>
<s>
Some	O
uses	O
of	O
BitTorrent	B-Protocol
for	O
file	O
sharing	O
may	O
violate	O
laws	O
in	O
some	O
jurisdictions	O
(	O
see	O
legislation	O
section	O
)	O
.	O
</s>
<s>
BitTorrent	B-Protocol
Inc	O
.	O
has	O
obtained	O
a	O
number	O
of	O
licenses	O
from	O
Hollywood	O
studios	O
for	O
distributing	O
popular	O
content	O
from	O
their	O
websites	O
.	O
</s>
<s>
Sub	O
Pop	O
Records	O
releases	O
tracks	O
and	O
videos	O
via	O
BitTorrent	B-Protocol
Inc	O
.	O
to	O
distribute	O
its	O
1000+	O
albums	O
.	O
</s>
<s>
Babyshambles	O
and	O
The	O
Libertines	O
(	O
both	O
bands	O
associated	O
with	O
Pete	O
Doherty	O
)	O
have	O
extensively	O
used	O
torrents	B-Protocol
to	O
distribute	O
hundreds	O
of	O
demos	O
and	O
live	O
videos	O
.	O
</s>
<s>
US	O
industrial	O
rock	O
band	O
Nine	O
Inch	O
Nails	O
frequently	O
distributes	O
albums	O
via	O
BitTorrent	B-Protocol
.	O
</s>
<s>
Podcasting	O
software	O
is	O
starting	O
to	O
integrate	O
BitTorrent	B-Protocol
to	O
help	O
podcasters	O
deal	O
with	O
the	O
download	O
demands	O
of	O
their	O
MP3	O
"	O
radio	O
"	O
programs	O
.	O
</s>
<s>
Specifically	O
,	O
Juice	B-Application
and	O
Miro	B-Language
(	O
formerly	O
known	O
as	O
Democracy	B-Language
Player	I-Language
)	O
support	O
automatic	O
processing	O
of	O
.torrent	O
files	O
from	O
RSS	O
feeds	O
.	O
</s>
<s>
Similarly	O
,	O
some	O
BitTorrent	B-Protocol
clients	O
,	O
such	O
as	O
μTorrent	B-Application
,	O
are	O
able	O
to	O
process	O
web	B-General_Concept
feeds	I-General_Concept
and	O
automatically	O
download	O
content	O
found	O
within	O
them	O
.	O
</s>
<s>
DGM	O
Live	O
purchases	O
are	O
provided	O
via	O
BitTorrent	B-Protocol
.	O
</s>
<s>
VODO	O
,	O
a	O
service	O
which	O
distributes	O
"	O
free-to-share	O
"	O
movies	O
and	O
TV	O
shows	O
via	O
BitTorrent	B-Protocol
.	O
</s>
<s>
In	O
2008	O
,	O
the	O
CBC	O
became	O
the	O
first	O
public	O
broadcaster	O
in	O
North	O
America	O
to	O
make	O
a	O
full	O
show	O
(	O
Canada	O
's	O
Next	O
Great	O
Prime	O
Minister	O
)	O
available	O
for	O
download	O
using	O
BitTorrent	B-Protocol
.	O
</s>
<s>
The	O
Norwegian	O
Broadcasting	O
Corporation	O
(	O
NRK	O
)	O
has	O
since	O
March	O
2008	O
experimented	O
with	O
bittorrent	B-Protocol
distribution	O
,	O
available	O
online	O
.	O
</s>
<s>
The	O
Dutch	O
VPRO	B-Architecture
broadcasting	O
organization	O
released	O
four	O
documentaries	O
in	O
2009	O
and	O
2010	O
under	O
a	O
Creative	O
Commons	O
license	O
using	O
the	O
content	O
distribution	O
feature	O
of	O
the	O
Mininova	O
tracker	B-Protocol
.	O
</s>
<s>
The	O
Amazon	O
AWS	O
's	O
Simple	B-General_Concept
Storage	I-General_Concept
Service	I-General_Concept
(	O
S3	O
)	O
,	O
until	O
April	O
29	O
,	O
2021	O
,	O
had	O
supported	O
sharing	O
of	O
bucket	O
objects	O
with	O
BitTorrent	B-Protocol
protocols	I-Protocol
.	O
</s>
<s>
After	O
April	O
29	O
,	O
2022	O
,	O
BitTorrent	B-Protocol
clients	O
will	O
no	O
longer	O
connect	O
to	O
Amazon	B-General_Concept
S3	I-General_Concept
.	O
</s>
<s>
Blizzard	O
Entertainment	O
uses	O
BitTorrent	B-Protocol
(	O
via	O
a	O
proprietary	O
client	O
called	O
the	O
"	O
Blizzard	O
Downloader	O
"	O
,	O
associated	O
with	O
the	O
Blizzard	O
"	O
BattleNet	O
"	O
network	O
)	O
to	O
distribute	O
content	O
and	O
patches	O
for	O
Diablo	B-Application
III	I-Application
,	O
StarCraft	B-Application
II	I-Application
and	O
World	B-Protocol
of	I-Protocol
Warcraft	I-Protocol
,	O
including	O
the	O
games	O
themselves	O
.	O
</s>
<s>
Wargaming	O
uses	O
BitTorrent	B-Protocol
in	O
their	O
popular	O
titles	O
World	B-Application
of	I-Application
Tanks	I-Application
,	O
World	B-Application
of	I-Application
Warships	I-Application
and	O
World	B-Application
of	I-Application
Warplanes	I-Application
to	O
distribute	O
game	O
updates	O
.	O
</s>
<s>
CCP	O
Games	O
,	O
maker	O
of	O
the	O
space	O
simulation	O
MMORPG	O
Eve	B-Protocol
Online	I-Protocol
,	O
has	O
announced	O
that	O
a	O
new	O
launcher	O
will	O
be	O
released	O
that	O
is	O
based	O
on	O
BitTorrent	B-Protocol
.	O
</s>
<s>
Many	O
software	O
games	O
,	O
especially	O
those	O
whose	O
large	O
size	O
makes	O
them	O
difficult	O
to	O
host	O
due	O
to	O
bandwidth	O
limits	O
,	O
extremely	O
frequent	O
downloads	O
,	O
and	O
unpredictable	O
changes	O
in	O
network	O
traffic	O
,	O
will	O
distribute	O
instead	O
a	O
specialized	O
,	O
stripped	O
down	O
BitTorrent	B-Protocol
client	O
with	O
enough	O
functionality	O
to	O
download	O
the	O
game	O
from	O
the	O
other	O
running	O
clients	O
and	O
the	O
primary	O
server	O
(	O
which	O
is	O
maintained	O
in	O
case	O
not	O
enough	O
peers	O
are	O
available	O
)	O
.	O
</s>
<s>
Many	O
major	O
open	B-Application
source	I-Application
and	O
free	B-Application
software	I-Application
projects	O
encourage	O
BitTorrent	B-Protocol
as	O
well	O
as	O
conventional	O
downloads	O
of	O
their	O
products	O
(	O
via	O
HTTP	B-Protocol
,	O
FTP	B-Protocol
etc	O
.	O
)	O
</s>
<s>
Resilio	O
Sync	O
is	O
a	O
BitTorrent-based	O
folder-syncing	O
tool	O
which	O
can	O
act	O
as	O
an	O
alternative	O
to	O
server-based	O
synchronisation	O
services	O
such	O
as	O
Dropbox	B-Application
.	O
</s>
<s>
The	O
British	O
government	O
used	O
BitTorrent	B-Protocol
to	O
distribute	O
details	O
about	O
how	O
the	O
tax	O
money	O
of	O
British	O
citizens	O
was	O
spent	O
.	O
</s>
<s>
Florida	O
State	O
University	O
uses	O
BitTorrent	B-Protocol
to	O
distribute	O
large	O
scientific	O
data	B-General_Concept
sets	O
to	O
its	O
researchers	O
.	O
</s>
<s>
Many	O
universities	O
that	O
have	O
BOINC	B-Operating_System
distributed	B-Architecture
computing	I-Architecture
projects	O
have	O
used	O
the	O
BitTorrent	B-Protocol
functionality	O
of	O
the	O
client-server	O
system	O
to	O
reduce	O
the	O
bandwidth	O
costs	O
of	O
distributing	O
the	O
client-side	O
applications	O
used	O
to	O
process	O
the	O
scientific	O
data	B-General_Concept
.	O
</s>
<s>
If	O
a	O
BOINC	B-Operating_System
distributed	B-Architecture
computing	I-Architecture
application	O
needs	O
to	O
be	O
updated	O
(	O
or	O
merely	O
sent	O
to	O
a	O
user	O
)	O
,	O
it	O
can	O
do	O
so	O
with	O
little	O
impact	O
on	O
the	O
BOINC	B-Operating_System
server	O
.	O
</s>
<s>
The	O
developing	O
Human	O
Connectome	O
Project	O
uses	O
BitTorrent	B-Protocol
to	O
share	O
their	O
.	O
</s>
<s>
Facebook	O
uses	O
BitTorrent	B-Protocol
to	O
distribute	O
updates	O
to	O
Facebook	O
servers	O
.	O
</s>
<s>
Twitter	O
uses	O
BitTorrent	B-Protocol
to	O
distribute	O
updates	O
to	O
Twitter	O
servers	O
.	O
</s>
<s>
The	O
Internet	O
Archive	O
added	O
BitTorrent	B-Protocol
to	O
its	O
file	O
download	O
options	O
for	O
over	O
1.3million	O
existing	O
files	O
,	O
and	O
all	O
newly	O
uploaded	O
files	O
,	O
in	O
August	O
2012	O
.	O
</s>
<s>
By	O
early	O
2015	O
,	O
AT&T	O
estimated	O
that	O
BitTorrent	B-Protocol
accounted	O
for	O
20%	O
of	O
all	O
broadband	O
traffic	O
.	O
</s>
<s>
Routers	O
that	O
use	O
network	B-Protocol
address	I-Protocol
translation	I-Protocol
(	O
NAT	O
)	O
must	O
maintain	O
tables	O
of	O
source	O
and	O
destination	O
IP	B-Protocol
addresses	I-Protocol
and	O
ports	O
.	O
</s>
<s>
Because	O
BitTorrent	B-Protocol
frequently	O
contacts	O
20	O
–	O
30	O
servers	O
per	O
second	O
,	O
the	O
NAT	O
tables	O
of	O
some	O
consumer-grade	O
routers	O
are	O
rapidly	O
filled	O
.	O
</s>
<s>
Although	O
the	O
protocol	O
itself	O
is	O
legal	O
,	O
problems	O
stem	O
from	O
using	O
the	O
protocol	O
to	O
traffic	O
copyright	O
infringing	O
works	O
,	O
since	O
BitTorrent	B-Protocol
is	O
often	O
used	O
to	O
download	O
otherwise	O
paid	O
content	O
,	O
such	O
as	O
movies	O
and	O
video	O
games	O
.	O
</s>
<s>
There	O
has	O
been	O
much	O
controversy	O
over	O
the	O
use	O
of	O
BitTorrent	B-Protocol
trackers	I-Protocol
.	O
</s>
<s>
BitTorrent	B-Protocol
metafiles	O
themselves	O
do	O
not	O
store	O
file	O
contents	O
.	O
</s>
<s>
Whether	O
the	O
publishers	O
of	O
BitTorrent	B-Protocol
metafiles	O
violate	O
copyrights	O
by	O
linking	O
to	O
copyrighted	O
works	O
without	O
the	O
authorization	O
of	O
copyright	O
holders	O
is	O
controversial	O
.	O
</s>
<s>
Various	O
jurisdictions	O
have	O
pursued	O
legal	O
action	O
against	O
websites	O
that	O
host	O
BitTorrent	B-Protocol
trackers	I-Protocol
.	O
</s>
<s>
BitTorrent	B-Protocol
search	B-Application
engine	I-Application
The	B-Application
Pirate	I-Application
Bay	I-Application
torrent	B-Protocol
website	O
,	O
formed	O
by	O
a	O
Swedish	O
group	O
,	O
is	O
noted	O
for	O
the	O
"	O
legal	O
"	O
section	O
of	O
its	O
website	O
in	O
which	O
letters	O
and	O
replies	O
on	O
the	O
subject	O
of	O
alleged	O
copyright	O
infringements	O
are	O
publicly	O
displayed	O
.	O
</s>
<s>
On	O
31	O
May	O
2006	O
,	O
The	B-Application
Pirate	I-Application
Bay	I-Application
's	O
servers	O
in	O
Sweden	O
were	O
raided	O
by	O
Swedish	O
police	O
on	O
allegations	O
by	O
the	O
MPAA	O
of	O
copyright	O
infringement	O
;	O
however	O
,	O
the	O
tracker	B-Protocol
was	O
up	O
and	O
running	O
again	O
three	O
days	O
later	O
.	O
</s>
<s>
In	O
the	O
study	O
used	O
to	O
value	O
NBC	O
Universal	O
in	O
its	O
merger	O
with	O
Comcast	O
,	O
Envisional	O
examined	O
the	O
10,000	O
torrent	B-Protocol
swarms	O
managed	O
by	O
PublicBT	O
which	O
had	O
the	O
most	O
active	O
downloaders	O
.	O
</s>
<s>
In	O
the	O
United	O
States	O
,	O
more	O
than	O
200,000	O
lawsuits	O
have	O
been	O
filed	O
for	O
copyright	O
infringement	O
on	O
BitTorrent	B-Protocol
since	O
2010	O
.	O
</s>
<s>
In	O
the	O
United	O
Kingdom	O
,	O
on	O
30	O
April	O
2012	O
,	O
the	O
High	O
Court	O
of	O
Justice	O
ordered	O
five	O
ISPs	O
to	O
block	O
The	B-Application
Pirate	I-Application
Bay	I-Application
.	O
</s>
<s>
One	O
concern	O
is	O
the	O
UDP	B-Protocol
flood	O
attack	O
.	O
</s>
<s>
BitTorrent	B-Protocol
implementations	O
often	O
use	O
μTP	B-Protocol
for	O
their	O
communication	O
.	O
</s>
<s>
To	O
achieve	O
high	O
bandwidths	O
,	O
the	O
underlying	O
protocol	O
used	O
is	O
UDP	B-Protocol
,	O
which	O
allows	O
spoofing	O
of	O
source	O
addresses	O
of	O
internet	O
traffic	O
.	O
</s>
<s>
It	O
has	O
been	O
possible	O
to	O
carry	O
out	O
denial-of-service	O
attacks	O
in	O
a	O
P2P	O
lab	O
environment	O
,	O
where	O
users	O
running	O
BitTorrent	B-Protocol
clients	O
act	O
as	O
amplifiers	O
for	O
an	O
attack	O
at	O
another	O
service	O
.	O
</s>
<s>
Several	O
studies	O
on	O
BitTorrent	B-Protocol
found	O
files	O
available	O
for	O
download	O
containing	O
malware	O
.	O
</s>
<s>
Another	O
study	O
claims	O
that	O
as	O
much	O
as	O
14.5	O
%	O
of	O
BitTorrent	B-Protocol
downloads	O
contain	O
zero-day	O
malware	O
,	O
and	O
that	O
BitTorrent	B-Protocol
was	O
used	O
as	O
the	O
distribution	O
mechanism	O
for	O
47%	O
of	O
all	O
zero-day	O
malware	O
they	O
have	O
found	O
.	O
</s>
