<s>
A	O
TCP	B-Protocol
sequence	I-Protocol
prediction	I-Protocol
attack	I-Protocol
is	O
an	O
attempt	O
to	O
predict	O
the	O
sequence	B-Protocol
number	I-Protocol
used	O
to	O
identify	O
the	O
packets	B-Protocol
in	O
a	O
TCP	B-Protocol
connection	I-Protocol
,	O
which	O
can	O
be	O
used	O
to	O
counterfeit	O
packets	B-Protocol
.	O
</s>
<s>
The	O
attacker	O
hopes	O
to	O
correctly	O
guess	O
the	O
sequence	B-Protocol
number	I-Protocol
to	O
be	O
used	O
by	O
the	O
sending	B-Device
host	I-Device
.	O
</s>
<s>
If	O
they	O
can	O
do	O
this	O
,	O
they	O
will	O
be	O
able	O
to	O
send	O
counterfeit	O
packets	B-Protocol
to	O
the	O
receiving	O
host	O
which	O
will	O
seem	O
to	O
originate	O
from	O
the	O
sending	B-Device
host	I-Device
,	O
even	O
though	O
the	O
counterfeit	O
packets	B-Protocol
may	O
in	O
fact	O
originate	O
from	O
some	O
third	O
host	O
controlled	O
by	O
the	O
attacker	O
.	O
</s>
<s>
One	O
possible	O
way	O
for	O
this	O
to	O
occur	O
is	O
for	O
the	O
attacker	O
to	O
listen	O
to	O
the	O
conversation	O
occurring	O
between	O
the	O
trusted	O
hosts	O
,	O
and	O
then	O
to	O
issue	O
packets	B-Protocol
using	O
the	O
same	O
source	O
IP	B-Protocol
address	I-Protocol
.	O
</s>
<s>
By	O
monitoring	O
the	O
traffic	O
before	O
an	O
attack	O
is	O
mounted	O
,	O
the	O
malicious	O
host	O
can	O
figure	O
out	O
the	O
correct	O
sequence	B-Protocol
number	I-Protocol
.	O
</s>
<s>
After	O
the	O
IP	B-Protocol
address	I-Protocol
and	O
the	O
correct	O
sequence	B-Protocol
number	I-Protocol
are	O
known	O
,	O
it	O
is	O
basically	O
a	O
race	O
between	O
the	O
attacker	O
and	O
the	O
trusted	O
host	O
to	O
get	O
the	O
correct	O
packet	B-Protocol
sent	O
.	O
</s>
<s>
Once	O
the	O
attacker	O
has	O
control	O
over	O
the	O
connection	O
,	O
they	O
are	O
able	O
to	O
send	O
counterfeit	O
packets	B-Protocol
without	O
getting	O
a	O
response	O
.	O
</s>
<s>
If	O
an	O
attacker	O
can	O
cause	O
delivery	O
of	O
counterfeit	O
packets	B-Protocol
of	O
this	O
sort	O
,	O
they	O
may	O
be	O
able	O
to	O
cause	O
various	O
sorts	O
of	O
mischief	O
,	O
including	O
the	O
injection	O
into	O
an	O
existing	O
TCP	B-Protocol
connection	I-Protocol
of	O
data	O
of	O
the	O
attacker	O
's	O
choosing	O
,	O
and	O
the	O
premature	O
closure	O
of	O
an	O
existing	O
TCP	B-Protocol
connection	I-Protocol
by	O
the	O
injection	O
of	O
counterfeit	O
packets	B-Protocol
with	O
the	O
RST	O
bit	O
set	O
.	O
</s>
<s>
Theoretically	O
,	O
other	O
information	O
such	O
as	O
timing	O
differences	O
or	O
information	O
from	O
lower	O
protocol	O
layers	O
could	O
allow	O
the	O
receiving	O
host	O
to	O
distinguish	O
authentic	O
TCP	O
packets	B-Protocol
from	O
the	O
sending	B-Device
host	I-Device
and	O
counterfeit	O
TCP	O
packets	B-Protocol
with	O
the	O
correct	O
sequence	B-Protocol
number	I-Protocol
sent	O
by	O
the	O
attacker	O
.	O
</s>
<s>
If	O
such	O
other	O
information	O
is	O
available	O
to	O
the	O
receiving	O
host	O
,	O
if	O
the	O
attacker	O
can	O
also	O
fake	O
that	O
other	O
information	O
,	O
and	O
if	O
the	O
receiving	O
host	O
gathers	O
and	O
uses	O
the	O
information	O
correctly	O
,	O
then	O
the	O
receiving	O
host	O
may	O
be	O
fairly	O
immune	O
to	O
TCP	B-Protocol
sequence	I-Protocol
prediction	I-Protocol
attacks	I-Protocol
.	O
</s>
<s>
Usually	O
this	O
is	O
not	O
the	O
case	O
,	O
so	O
the	O
TCP	O
sequence	B-Protocol
number	I-Protocol
is	O
the	O
primary	O
means	O
of	O
protection	O
of	O
TCP	O
traffic	O
against	O
these	O
types	O
of	O
attack	O
.	O
</s>
<s>
Another	O
solution	O
to	O
this	O
type	O
of	O
attack	O
is	O
to	O
configure	O
any	O
router	B-Protocol
or	O
firewall	B-Application
to	O
not	O
allow	O
packets	B-Protocol
to	O
come	O
in	O
from	O
an	O
external	O
source	O
but	O
with	O
an	O
internal	O
IP	B-Protocol
address	I-Protocol
.	O
</s>
