<s>
Google	B-Application
Public	B-Operating_System
DNS	I-Operating_System
is	O
a	O
Domain	B-Protocol
Name	I-Protocol
System	I-Protocol
(	O
DNS	B-Protocol
)	O
service	O
offered	O
to	O
Internet	O
users	O
worldwide	O
by	O
Google	B-Application
.	I-Application
</s>
<s>
It	O
functions	O
as	O
a	O
recursive	O
name	B-Protocol
server	I-Protocol
.	O
</s>
<s>
Google	B-Application
Public	B-Operating_System
DNS	I-Operating_System
was	O
announced	O
on	O
December	O
3	O
,	O
2009	O
,	O
in	O
an	O
effort	O
described	O
as	O
"	O
making	O
the	O
web	O
faster	O
and	O
more	O
secure.	O
"	O
</s>
<s>
As	O
of	O
2018	O
,	O
it	O
is	O
the	O
largest	O
public	B-Operating_System
DNS	I-Operating_System
service	O
in	O
the	O
world	O
,	O
handling	O
over	O
a	O
trillion	O
queries	O
per	O
day	O
.	O
</s>
<s>
Google	B-Application
Public	B-Operating_System
DNS	I-Operating_System
is	O
not	O
related	O
to	O
Google	B-Application
Cloud	O
DNS	B-Protocol
,	O
which	O
is	O
a	O
DNS	B-Protocol
hosting	O
service	O
.	O
</s>
<s>
The	B-Application
Google	I-Application
Public	B-Operating_System
DNS	I-Operating_System
service	O
operates	O
recursive	O
name	B-Protocol
servers	I-Protocol
for	O
public	O
use	O
at	O
the	O
four	O
IP	B-Protocol
addresses	I-Protocol
listed	O
below	O
.	O
</s>
<s>
These	O
addresses	O
are	O
mapped	O
to	O
the	O
nearest	O
operational	O
server	O
by	O
anycast	B-Protocol
routing	B-Protocol
.	O
</s>
<s>
The	O
service	O
does	O
not	O
use	O
conventional	O
DNS	B-Protocol
name	I-Protocol
server	O
software	O
,	O
such	O
as	O
BIND	B-Protocol
,	O
instead	O
relying	O
on	O
a	O
custom-designed	O
implementation	O
,	O
conforming	O
to	O
the	O
DNS	B-Protocol
standards	O
set	O
forth	O
by	O
the	O
IETF	O
.	O
</s>
<s>
It	O
fully	O
supports	O
the	O
DNSSEC	B-Protocol
protocol	O
since	O
19	O
March	O
2013	O
.	O
</s>
<s>
Previously	O
,	O
Google	B-Application
Public	B-Operating_System
DNS	I-Operating_System
accepted	O
and	O
forwarded	O
DNSSEC-formatted	O
messages	O
but	O
did	O
not	O
perform	O
validation	O
.	O
</s>
<s>
Some	O
DNS	B-Protocol
providers	O
practice	O
DNS	B-Protocol
hijacking	I-Protocol
while	O
processing	O
queries	O
,	O
redirecting	O
web	O
browsers	O
to	O
an	O
advertisement	O
site	O
operated	O
by	O
the	O
provider	O
when	O
a	O
nonexistent	O
domain	O
name	O
is	O
queried	O
.	O
</s>
<s>
The	B-Application
Google	I-Application
service	O
correctly	O
replies	O
with	O
a	O
non-existent	O
domain	O
(	O
NXDOMAIN	O
)	O
response	O
.	O
</s>
<s>
The	B-Application
Google	I-Application
service	O
also	O
addresses	O
DNS	B-Protocol
security	O
.	O
</s>
<s>
A	O
common	O
attack	O
vector	O
is	O
to	O
interfere	O
with	O
a	O
DNS	B-Protocol
service	O
to	O
achieve	O
redirection	O
of	O
web	O
pages	O
from	O
legitimate	O
to	O
malicious	O
servers	O
.	O
</s>
<s>
Google	B-Application
documents	O
efforts	O
to	O
be	O
resistant	O
to	O
DNS	B-Protocol
cache	O
poisoning	O
,	O
including	O
“	O
Kaminsky	O
Flaw	O
”	O
attacks	O
as	O
well	O
as	O
denial-of-service	O
attacks	O
.	O
</s>
<s>
The	B-Application
Google	I-Application
Public	O
DNS64	O
service	O
operates	O
recursive	O
name	B-Protocol
servers	I-Protocol
for	O
public	O
use	O
at	O
the	O
two	O
IP	B-Protocol
addresses	I-Protocol
listed	O
below	O
for	O
use	O
with	O
NAT64	B-Protocol
.	O
</s>
<s>
Google	B-Application
stated	O
that	O
for	O
the	O
purposes	O
of	O
performance	O
and	O
security	O
,	O
the	O
querying	O
IP	B-Protocol
address	I-Protocol
will	O
be	O
deleted	O
after	O
24	O
–	O
48	O
hours	O
,	O
but	O
Internet	O
service	O
provider	O
(	O
ISP	O
)	O
and	O
location	B-Application
information	O
are	O
stored	O
permanently	O
on	O
their	O
servers	O
.	O
</s>
<s>
In	O
December	O
2009	O
,	O
Google	B-Application
Public	B-Operating_System
DNS	I-Operating_System
was	O
launched	O
with	O
its	O
announcement	O
on	O
the	O
Official	O
Google	B-Application
Blog	O
by	O
product	O
manager	O
Prem	O
Ramaswami	O
,	O
with	O
an	O
additional	O
post	O
on	O
the	B-Application
Google	I-Application
Code	O
blog	O
.	O
</s>
<s>
In	O
January	O
2019	O
,	O
Google	B-Application
Public	B-Operating_System
DNS	I-Operating_System
adopted	O
the	O
DNS	B-Protocol
over	I-Protocol
TLS	I-Protocol
protocol	O
.	O
</s>
<s>
At	O
the	O
launch	O
of	O
Google	B-Application
Public	B-Operating_System
DNS	I-Operating_System
,	O
it	O
did	O
not	O
directly	O
support	O
DNSSEC	B-Protocol
.	O
</s>
<s>
This	O
was	O
upgraded	O
on	O
28	O
January	O
2013	O
,	O
when	O
Google	B-Application
's	I-Application
DNS	B-Protocol
servers	I-Protocol
silently	O
started	O
providing	O
DNSSEC	B-Protocol
validation	O
information	O
,	O
but	O
only	O
if	O
the	O
client	O
explicitly	O
set	O
the	O
DNSSEC	B-Protocol
OK	O
(	O
DO	O
)	O
flag	O
on	O
its	O
query	O
.	O
</s>
<s>
This	O
service	O
requiring	O
a	O
client-side	O
flag	O
was	O
replaced	O
on	O
6	O
May	O
2013	O
with	O
full	O
DNSSEC	B-Protocol
validation	O
by	O
default	O
,	O
meaning	O
all	O
queries	O
will	O
be	O
validated	O
unless	O
clients	O
explicitly	O
opt-out	O
.	O
</s>
<s>
Since	O
June	O
2014	O
,	O
Google	B-Application
Public	B-Operating_System
DNS	I-Operating_System
automatically	O
detects	O
nameservers	B-Protocol
that	O
support	O
EDNS	B-Protocol
Client	I-Protocol
Subnet	I-Protocol
(	O
ECS	B-Protocol
)	O
options	O
as	O
defined	O
in	O
the	O
IETF	O
draft	O
(	O
by	O
probing	O
name	B-Protocol
servers	I-Protocol
at	O
a	O
low	O
rate	O
with	O
ECS	B-Protocol
queries	O
and	O
caching	O
the	O
ECS	B-Protocol
capability	O
)	O
,	O
and	O
will	O
send	O
queries	O
with	O
ECS	B-Protocol
options	O
to	O
such	O
name	B-Protocol
servers	I-Protocol
automatically	O
.	O
</s>
<s>
In	O
March	O
2014	O
,	O
use	O
of	O
Google	B-Application
Public	B-Operating_System
DNS	I-Operating_System
was	O
blocked	O
in	O
Turkey	O
after	O
it	O
was	O
used	O
to	O
circumvent	O
the	O
blocking	O
of	O
Twitter	B-Application
,	O
which	O
took	O
effect	O
on	O
20	O
March	O
2014	O
under	O
court	O
order	O
.	O
</s>
<s>
The	O
block	O
was	O
the	O
result	O
of	O
earlier	O
remarks	O
by	O
Prime	O
Minister	O
Tayyip	O
Erdogan	O
who	O
vowed	O
to	O
"	O
wipe	O
out	O
Twitter	B-Application
"	O
following	O
damaging	O
allegations	O
of	O
corruption	O
in	O
his	O
inner	O
circle	O
.	O
</s>
<s>
The	O
method	O
became	O
popular	O
after	O
it	O
was	O
determined	O
that	O
a	O
simple	O
domain	O
name	O
block	O
was	O
used	O
to	O
enforce	O
the	O
ban	O
,	O
which	O
would	O
easily	O
be	O
bypassed	O
by	O
using	O
an	O
alternate	O
DNS	B-Protocol
resolver	O
.	O
</s>
<s>
Activists	O
distributed	O
information	O
on	O
how	O
to	O
use	O
the	O
service	O
,	O
and	O
spray-painted	O
the	O
IP	B-Protocol
addresses	I-Protocol
used	O
by	O
the	O
service	O
as	O
graffiti	B-Application
on	O
buildings	O
.	O
</s>
<s>
Following	O
the	O
discovery	O
of	O
this	O
method	O
,	O
Google	B-Application
Public	B-Operating_System
DNS	I-Operating_System
was	O
blocked	O
entirely	O
.	O
</s>
