<s>
TCP/IP	B-Protocol
stack	I-Protocol
fingerprinting	I-Protocol
is	O
the	O
remote	O
detection	O
of	O
the	O
characteristics	O
of	O
a	O
TCP/IP	B-Protocol
stack	I-Protocol
implementation	O
.	O
</s>
<s>
The	O
combination	O
of	O
parameters	O
may	O
then	O
be	O
used	O
to	O
infer	O
the	O
remote	O
machine	O
's	O
operating	O
system	O
(	O
aka	O
,	O
OS	B-Protocol
fingerprinting	I-Protocol
)	O
,	O
or	O
incorporated	O
into	O
a	O
device	B-Protocol
fingerprint	I-Protocol
.	O
</s>
<s>
Certain	O
parameters	O
within	O
the	O
TCP	B-Protocol
protocol	I-Protocol
definition	O
are	O
left	O
up	O
to	O
the	O
implementation	O
.	O
</s>
<s>
By	O
collecting	O
and	O
examining	O
these	O
values	O
,	O
one	O
may	O
differentiate	O
among	O
various	O
operating	O
systems	O
,	O
and	O
implementations	O
of	O
TCP/IP	B-Protocol
.	O
</s>
<s>
Just	O
inspecting	O
the	O
Initial	O
TTL	B-Protocol
and	O
window	O
size	O
fields	O
is	O
often	O
enough	O
in	O
order	O
to	O
successfully	O
identify	O
an	O
operating	O
system	O
,	O
which	O
eases	O
the	O
task	O
of	O
performing	O
manual	O
OS	B-Protocol
fingerprinting	I-Protocol
.	O
</s>
<s>
Examples	O
include	O
blocking	O
address	O
masks	O
and	O
timestamps	O
from	O
outgoing	O
ICMP	B-Protocol
control-message	O
traffic	O
,	O
and	O
blocking	O
ICMP	B-Protocol
echo	I-Protocol
replies	I-Protocol
.	O
</s>
<s>
Disallowing	O
TCP/IP	B-Protocol
fingerprinting	O
provides	O
protection	O
from	O
vulnerability	O
scanners	O
looking	O
to	O
target	O
machines	O
running	O
a	O
certain	O
operating	O
system	O
.	O
</s>
<s>
Blocking	O
those	O
ICMP	B-Protocol
messages	O
is	O
only	O
one	O
of	O
an	O
array	O
of	O
defenses	O
required	O
for	O
full	O
protection	O
against	O
attacks	O
.	O
</s>
<s>
Targeting	O
the	O
ICMP	B-Protocol
datagram	O
,	O
an	O
obfuscator	O
running	O
on	O
top	O
of	O
IP	O
in	O
the	O
internet	O
layer	O
acts	O
as	O
a	O
"	O
scrubbing	O
tool	O
"	O
to	O
confuse	O
the	O
TCP/IP	B-Protocol
fingerprinting	O
data	O
.	O
</s>
<s>
These	O
exist	O
for	O
Microsoft	B-Application
Windows	I-Application
,	O
Linux	B-Application
and	O
FreeBSD	B-Operating_System
.	O
</s>
<s>
Zardaxt.py	O
–	O
Passive	O
open	O
source	O
TCP/IP	B-Protocol
Fingerprinting	O
Tool	O
.	O
</s>
<s>
Ettercap	B-Language
–	O
passive	O
TCP/IP	B-Protocol
stack	I-Protocol
fingerprinting	I-Protocol
.	O
</s>
<s>
Nmap	B-Language
–	O
comprehensive	O
active	O
stack	O
fingerprinting	O
.	O
</s>
<s>
p0f	B-Protocol
–	O
comprehensive	O
passive	O
TCP/IP	B-Protocol
stack	I-Protocol
fingerprinting	I-Protocol
.	O
</s>
<s>
PacketFence	B-Protocol
–	O
open	O
source	O
NAC	O
with	O
passive	O
DHCP	O
fingerprinting	O
.	O
</s>
<s>
Satori	O
–	O
passive	O
CDP	B-Protocol
,	O
DHCP	O
,	O
ICMP	B-Protocol
,	O
HPSP	O
,	O
HTTP	B-Protocol
,	O
TCP/IP	B-Protocol
and	O
other	O
stack	O
fingerprinting	O
.	O
</s>
<s>
XProbe2	O
–	O
active	O
TCP/IP	B-Protocol
stack	I-Protocol
fingerprinting	I-Protocol
.	O
</s>
