<s>
NTP	B-Architecture
server	I-Architecture
misuse	I-Architecture
and	I-Architecture
abuse	I-Architecture
covers	O
a	O
number	O
of	O
practices	O
which	O
cause	O
damage	O
or	O
degradation	O
to	O
a	O
Network	B-Protocol
Time	I-Protocol
Protocol	I-Protocol
(	O
NTP	B-Protocol
)	O
server	O
,	O
ranging	O
from	O
flooding	O
it	O
with	O
traffic	O
(	O
effectively	O
a	O
DDoS	O
attack	O
)	O
or	O
violating	O
the	O
server	O
's	O
access	O
policy	O
or	O
the	O
NTP	B-Protocol
.	O
</s>
<s>
One	O
incident	O
was	O
branded	O
NTP	B-Architecture
vandalism	I-Architecture
in	O
an	O
open	O
letter	O
from	O
Poul-Henning	O
Kamp	O
to	O
the	O
router	B-Protocol
manufacturer	O
D-Link	B-General_Concept
in	O
2006	O
.	O
</s>
<s>
A	O
came	O
to	O
note	O
at	O
the	O
end	O
of	O
2013	O
,	O
when	O
NTP	B-Protocol
servers	I-Protocol
were	O
used	O
as	O
part	O
of	O
amplification	O
denial-of-service	O
attacks	O
.	O
</s>
<s>
Some	O
NTP	B-Protocol
servers	I-Protocol
would	O
respond	O
to	O
a	O
single	O
"	O
monlist	O
"	O
UDP	O
request	O
packet	O
,	O
with	O
packets	O
describing	O
up	O
to	O
600	O
associations	O
.	O
</s>
<s>
The	O
most	O
troublesome	O
problems	O
have	O
involved	O
NTP	B-Protocol
server	I-Protocol
addresses	O
hardcoded	O
in	O
the	O
firmware	B-Application
of	O
consumer	O
networking	O
devices	O
.	O
</s>
<s>
As	O
major	O
manufacturers	O
and	O
OEMs	O
have	O
produced	O
hundreds	O
of	O
thousands	O
of	O
devices	O
using	O
NTP	B-Protocol
coupled	O
with	O
customers	O
almost	O
never	O
upgrading	O
the	O
firmware	B-Application
of	O
these	O
devices	O
,	O
NTP	B-Protocol
query	O
storms	O
problems	O
will	O
persist	O
for	O
as	O
long	O
as	O
the	O
devices	O
are	O
in	O
service	O
.	O
</s>
<s>
When	O
placed	O
behind	O
aggressive	O
firewalls	B-Application
that	O
block	O
the	O
server	O
responses	O
,	O
this	O
implementation	O
leads	O
to	O
a	O
never-ending	O
stream	O
of	O
client	O
requests	O
to	O
the	O
variously	O
blocked	O
NTP	B-Protocol
servers	I-Protocol
.	O
</s>
<s>
Such	O
over-eager	O
clients	O
(	O
particularly	O
those	O
polling	O
once	O
per	O
second	O
)	O
commonly	O
make	O
up	O
more	O
than	O
50%	O
of	O
the	O
traffic	O
of	O
public	O
NTP	B-Protocol
servers	I-Protocol
,	O
despite	O
being	O
a	O
minuscule	O
fraction	O
of	O
the	O
total	O
clients	O
.	O
</s>
<s>
Examples	O
of	O
this	O
backing	O
down	O
method	O
can	O
be	O
found	O
in	O
the	O
TCP	B-Protocol
specification	O
for	O
connection	O
establishment	O
,	O
zero-window	O
probing	O
,	O
and	O
keepalive	O
transmissions	O
.	O
</s>
<s>
The	O
first	O
widely	O
known	O
case	O
of	O
NTP	B-Protocol
server	I-Protocol
problems	O
began	O
in	O
May	O
2003	O
,	O
when	O
Netgear	O
's	O
hardware	O
products	O
flooded	O
the	O
University	O
of	O
Madison	O
's	O
NTP	B-Protocol
server	I-Protocol
with	O
requests	O
.	O
</s>
<s>
Subsequent	O
investigation	O
revealed	O
that	O
four	O
models	O
of	O
Netgear	O
routers	B-Protocol
were	O
the	O
source	O
of	O
the	O
problem	O
.	O
</s>
<s>
It	O
was	O
found	O
that	O
the	O
SNTP	O
(	O
Simple	O
NTP	B-Protocol
)	O
client	O
in	O
the	O
routers	B-Protocol
has	O
two	O
serious	O
flaws	O
.	O
</s>
<s>
First	O
,	O
it	O
relies	O
on	O
a	O
single	O
NTP	B-Protocol
server	I-Protocol
(	O
at	O
the	O
University	O
of	O
Wisconsin	O
–	O
Madison	O
)	O
whose	O
IP	O
address	O
was	O
hard-coded	O
in	O
the	O
firmware	B-Application
.	O
</s>
<s>
Netgear	O
has	O
released	O
firmware	B-Application
updates	O
for	O
the	O
affected	O
products	O
(	O
DG814	O
,	O
HR314	O
,	O
MR814	O
and	O
RP614	O
)	O
which	O
query	O
Netgear	O
's	O
own	O
servers	O
,	O
poll	O
only	O
once	O
every	O
ten	O
minutes	O
,	O
and	O
give	O
up	O
after	O
five	O
failures	O
.	O
</s>
<s>
Most	O
consumers	O
will	O
never	O
update	O
their	O
router	B-Protocol
's	O
firmware	B-Application
,	O
particularly	O
if	O
the	O
device	O
seems	O
to	O
be	O
operating	O
properly	O
.	O
</s>
<s>
The	O
University	O
of	O
Wisconsin	O
–	O
Madison	O
NTP	B-Protocol
server	I-Protocol
continues	O
to	O
receive	O
high	O
levels	O
of	O
traffic	O
from	O
Netgear	O
routers	B-Protocol
,	O
with	O
occasional	O
floods	O
of	O
up	O
to	O
100,000	O
packets-per-second	O
.	O
</s>
<s>
Also	O
in	O
2003	O
,	O
another	O
case	O
forced	O
the	O
NTP	B-Protocol
servers	I-Protocol
of	O
the	O
Australian	O
Commonwealth	O
Scientific	O
and	O
Industrial	O
Research	O
Organisation	O
's	O
(	O
CSIRO	O
)	O
National	O
Measurement	O
Laboratory	O
to	O
close	O
to	O
the	O
public	O
.	O
</s>
<s>
The	O
traffic	O
was	O
shown	O
to	O
come	O
from	O
a	O
bad	O
NTP	B-Protocol
implementation	O
in	O
some	O
SMC	O
router	B-Protocol
models	O
where	O
the	O
IP	O
address	O
of	O
the	O
CSIRO	O
server	O
was	O
embedded	O
in	O
the	O
firmware	B-Application
.	O
</s>
<s>
SMC	O
has	O
released	O
firmware	B-Application
updates	O
for	O
the	O
products	O
:	O
the	O
7004VBR	O
and	O
7004VWBR	O
models	O
are	O
known	O
to	O
be	O
affected	O
.	O
</s>
<s>
In	O
2005	O
Poul-Henning	O
Kamp	O
,	O
the	O
manager	O
of	O
the	O
only	O
Danish	O
Stratum	O
1	O
NTP	B-Protocol
server	I-Protocol
available	O
to	O
the	O
general	O
public	O
,	O
observed	O
a	O
huge	O
rise	O
in	O
traffic	O
and	O
discovered	O
that	O
between	O
75	O
and	O
90%	O
was	O
originating	O
with	O
D-Link	B-General_Concept
'	O
s	O
router	B-Protocol
products	O
.	O
</s>
<s>
Stratum	O
1	O
NTP	B-Protocol
servers	I-Protocol
receive	O
their	O
time	O
signal	O
from	O
an	O
accurate	O
external	O
source	O
,	O
such	O
as	O
a	O
GPS	O
receiver	O
,	O
radio	O
clock	O
,	O
or	O
a	O
calibrated	O
atomic	O
clock	O
.	O
</s>
<s>
A	O
home	O
networking	O
router	B-Protocol
does	O
not	O
meet	O
either	O
of	O
these	O
criteria	O
.	O
</s>
<s>
The	O
direct	O
use	O
of	O
this	O
and	O
other	O
Stratum	O
1	O
servers	O
by	O
D-Link	B-General_Concept
'	O
s	O
routers	B-Protocol
resulted	O
in	O
a	O
huge	O
rise	O
in	O
traffic	O
,	O
increasing	O
bandwidth	O
costs	O
and	O
server	O
load	O
.	O
</s>
<s>
With	O
the	O
increased	O
traffic	O
caused	O
by	O
the	O
D-Link	B-General_Concept
routers	B-Protocol
,	O
DIX	O
requested	O
he	O
pay	O
a	O
yearly	O
connection	O
fee	O
of	O
(	O
approximately	O
or	O
)	O
.	O
</s>
<s>
Kamp	O
contacted	O
D-Link	B-General_Concept
in	O
November	O
2005	O
,	O
hoping	O
to	O
get	O
them	O
to	O
fix	O
the	O
problem	O
and	O
compensate	O
him	O
for	O
the	O
time	O
and	O
money	O
he	O
spent	O
tracking	O
down	O
the	O
problem	O
and	O
the	O
bandwidth	O
charges	O
caused	O
by	O
D-Link	B-General_Concept
products	O
.	O
</s>
<s>
The	O
story	O
was	O
picked	O
up	O
by	O
Slashdot	O
,	O
Reddit	B-Application
and	O
other	O
news	O
sites	O
.	O
</s>
<s>
After	O
going	O
public	O
,	O
Kamp	O
realized	O
that	O
D-Link	B-General_Concept
routers	B-Protocol
were	O
directly	O
querying	O
other	O
Stratum	O
1	O
time	O
servers	O
,	O
violating	O
the	O
access	O
policies	O
of	O
at	O
least	O
43	O
of	O
them	O
in	O
the	O
process	O
.	O
</s>
<s>
On	O
April	O
27	O
,	O
2006	O
,	O
D-Link	B-General_Concept
and	O
Kamp	O
announced	O
that	O
they	O
had	O
"	O
amicably	O
resolved	O
"	O
their	O
dispute	O
.	O
</s>
<s>
Due	O
to	O
excessive	O
bandwidth	O
usage	O
,	O
averaging	O
upwards	O
of	O
20	O
GB	O
/	O
day	O
,	O
it	O
has	O
become	O
necessary	O
to	O
direct	O
external	O
usage	O
to	O
public	O
time	O
server	O
pools	O
,	O
such	O
as	O
ch.pool.ntp.org	O
.	O
</s>
<s>
,	O
access	O
to	O
the	O
server	O
is	O
blocked	O
entirely	O
for	O
the	O
NTP	B-Protocol
protocol	O
.	O
</s>
<s>
In	O
December	O
2016	O
,	O
the	O
operator	O
community	O
NTPPool.org	O
noticed	O
a	O
significant	O
increase	O
in	O
NTP	B-Protocol
traffic	O
,	O
starting	O
December	O
13	O
.	O
</s>
<s>
Investigation	O
showed	O
that	O
the	O
Snapchat	B-Application
application	O
running	O
on	O
iOS	B-Application
was	O
prone	O
to	O
querying	O
all	O
NTP	B-Protocol
servers	I-Protocol
that	O
were	O
hardcoded	O
into	O
a	O
third	O
party	O
iOS	B-Application
NTP	B-Protocol
library	O
,	O
and	O
that	O
a	O
request	O
to	O
a	O
Snapchat-owned	O
domain	O
followed	O
the	O
NTP	B-Protocol
request	O
flood	O
.	O
</s>
<s>
As	O
an	O
apology	O
and	O
to	O
assist	O
in	O
dealing	O
with	O
the	O
load	O
they	O
generated	O
,	O
Snap	O
also	O
contributed	O
timeservers	O
to	O
the	O
Australia	O
and	O
South	O
America	O
NTP	B-Protocol
pools	I-Protocol
.	O
</s>
<s>
As	O
a	O
positive	O
side	O
effect	O
,	O
the	O
NTP	B-Protocol
library	O
used	O
is	O
open	O
source	O
,	O
and	O
the	O
error-prone	O
default	O
settings	O
were	O
improved	O
after	O
feedback	O
from	O
the	O
NTP	B-Protocol
community	O
.	O
</s>
<s>
Firmware	B-Application
for	O
TP-Link	B-Application
Wi‑Fi	B-Device
extenders	I-Device
in	O
2016	O
and	O
2017	O
hardcoded	O
five	O
NTP	B-Protocol
servers	I-Protocol
,	O
including	O
Fukuoka	O
University	O
in	O
Japan	O
and	O
the	O
Australia	O
and	O
New	O
Zealand	O
NTP	B-Protocol
server	I-Protocol
pools	O
,	O
and	O
would	O
repeatedly	O
issue	O
one	O
NTP	B-Protocol
request	O
and	O
five	O
DNS	B-Application
requests	O
every	O
five	O
seconds	O
consuming	O
0.72	O
GB	O
per	O
month	O
per	O
device	O
.	O
</s>
<s>
The	O
issue	O
was	O
acknowledged	O
by	O
TP-Link	B-Application
'	O
s	O
branch	O
in	O
Japan	O
who	O
pushed	O
the	O
company	O
to	O
redesign	O
the	O
connectivity	O
test	O
and	O
issue	O
firmware	B-Application
updates	O
addressing	O
the	O
issue	O
for	O
affected	O
devices	O
.	O
</s>
<s>
The	O
affected	O
devices	O
are	O
unlikely	O
to	O
install	O
the	O
new	O
firmware	B-Application
as	O
WiFi	B-Device
extenders	I-Device
from	O
TP-Link	B-Application
does	O
not	O
install	O
firmware	B-Application
updates	O
automatically	O
,	O
nor	O
do	O
they	O
notify	O
the	O
owner	O
about	O
firmware	B-Application
update	O
availability	O
.	O
</s>
<s>
TP-Link	B-Application
firmware	B-Application
update	O
availability	O
also	O
varies	O
by	O
country	O
,	O
even	O
though	O
the	O
issue	O
affects	O
all	O
WiFi	O
range	O
extenders	O
sold	O
globally	O
.	O
</s>
<s>
The	O
servers	O
of	O
Fukuoka	O
University	O
are	O
reported	O
as	O
being	O
shut	O
down	O
sometime	O
between	O
February	O
and	O
April	O
2018	O
,	O
and	O
should	O
be	O
removed	O
from	O
the	O
NTP	B-Protocol
Public	O
Time	O
Server	O
Lists	O
.	O
</s>
<s>
One	O
such	O
mechanism	O
was	O
provided	O
by	O
extending	O
semantics	O
of	O
a	O
Reference	O
Identifier	O
field	O
in	O
an	O
NTP	B-Protocol
packet	O
when	O
a	O
Stratum	O
field	O
is	O
0	O
.	O
</s>
<s>
In	O
January	O
2006	O
,	O
RFC	O
4330	O
was	O
published	O
,	O
updating	O
details	O
of	O
the	O
SNTP	O
protocol	O
,	O
but	O
also	O
provisionally	O
clarifying	O
and	O
extending	O
the	O
related	O
NTP	B-Protocol
protocol	O
in	O
some	O
areas	O
.	O
</s>
<s>
The	O
new	O
requirements	O
of	O
the	O
NTP	B-Protocol
protocol	O
do	O
not	O
work	O
retroactively	O
,	O
and	O
old	O
clients	O
and	O
implementations	O
of	O
earlier	O
version	O
of	O
the	O
protocol	O
do	O
not	O
recognize	O
KoD	O
and	O
act	O
on	O
it	O
.	O
</s>
<s>
For	O
the	O
time	O
being	O
there	O
are	O
no	O
good	O
technical	O
means	O
to	O
counteract	O
misuse	O
of	O
NTP	B-Protocol
servers	I-Protocol
.	O
</s>
<s>
In	O
2015	O
,	O
due	O
to	O
possible	O
attacks	O
to	O
Network	B-Protocol
Time	I-Protocol
Protocol	I-Protocol
,	O
a	O
Network	B-Protocol
Time	I-Protocol
Security	I-Protocol
for	O
NTP	B-Protocol
(	O
Internet	O
Draft	O
draft-ietf-ntp-using-nts-for-ntp-19	O
)	O
was	O
proposed	O
using	O
a	O
Transport	B-Protocol
Layer	I-Protocol
Security	I-Protocol
implementation	O
.	O
</s>
<s>
On	O
June	O
21	O
,	O
2019	O
Cloudflare	B-Application
started	O
a	O
trial	O
service	O
around	O
the	O
world	O
,	O
based	O
on	O
a	O
previous	O
Internet	O
Draft	O
.	O
</s>
