<s>
SMBRelay	B-Protocol
and	O
SMBRelay2	B-Protocol
are	O
computer	B-Application
programs	I-Application
that	O
can	O
be	O
used	O
to	O
carry	O
out	O
SMB	B-Operating_System
man-in-the-middle	O
(	O
mitm	O
)	O
attacks	O
on	O
Windows	B-Application
machines	O
.	O
</s>
<s>
More	O
than	O
seven	O
years	O
after	O
its	O
release	O
,	O
Microsoft	O
released	O
a	O
patch	O
that	O
fixed	O
the	O
hole	O
exploited	O
by	O
SMBRelay	B-Protocol
.	O
</s>
<s>
This	O
fix	O
only	O
fixes	O
the	O
vulnerability	O
when	O
the	O
SMB	B-Operating_System
is	O
reflected	O
back	O
to	O
the	O
client	O
.	O
</s>
<s>
SMBrelay	B-Protocol
receives	O
a	O
connection	O
on	O
UDP	B-Protocol
port	B-Protocol
139	I-Protocol
and	O
relays	O
the	O
packets	O
between	O
the	O
client	O
and	O
server	O
of	O
the	O
connecting	O
Windows	B-Application
machine	O
to	O
the	O
originating	O
computer	O
's	O
port	B-Protocol
139	I-Protocol
.	O
</s>
<s>
After	O
connecting	O
and	O
authenticating	O
,	O
the	O
target	O
's	O
client	O
is	O
disconnected	O
and	O
SMBRelay	B-Protocol
binds	O
to	O
port	B-Protocol
139	I-Protocol
on	O
a	O
new	O
IP	B-Protocol
address	I-Protocol
.	O
</s>
<s>
This	O
relay	O
address	O
can	O
then	O
be	O
connected	O
to	O
directly	O
using	O
"	O
net	O
use	O
\\192.1.1.1	O
 "	O
and	O
then	O
used	O
by	O
all	O
of	O
the	O
networking	O
functions	O
built	O
into	O
Windows	B-Application
.	O
</s>
<s>
The	O
program	O
relays	O
all	O
of	O
the	O
SMB	B-Operating_System
traffic	O
,	O
excluding	O
negotiation	O
and	O
authentication	O
.	O
</s>
<s>
As	O
long	O
as	O
the	O
target	O
host	O
remains	O
connected	O
,	O
the	O
user	O
can	O
disconnect	O
from	O
and	O
reconnect	O
to	O
this	O
virtual	B-Operating_System
IP	I-Operating_System
.	O
</s>
<s>
SMBRelay	B-Protocol
collects	O
the	O
NTLM	O
password	O
hashes	B-Algorithm
and	O
writes	O
them	O
to	O
hashes.txt	O
in	O
a	O
format	O
usable	O
by	O
L0phtCrack	B-Application
for	O
cracking	O
at	O
a	O
later	O
time	O
.	O
</s>
<s>
As	O
port	B-Protocol
139	I-Protocol
is	O
a	O
privileged	O
port	B-Protocol
and	O
requires	O
administrator	B-Application
access	O
for	O
use	O
,	O
SMBRelay	B-Protocol
must	O
run	O
as	O
an	O
administrator	B-Application
access	O
account	O
.	O
</s>
<s>
However	O
,	O
since	O
port	B-Protocol
139	I-Protocol
is	O
needed	O
for	O
NetBIOS	B-Protocol
sessions	O
,	O
it	O
is	O
difficult	O
to	O
block	O
.	O
</s>
<s>
According	O
to	O
Sir	O
Dystic	O
,	O
"	O
The	O
problem	O
is	O
that	O
from	O
a	O
marketing	O
standpoint	O
,	O
Microsoft	O
wants	O
their	O
products	O
to	O
have	O
as	O
much	O
backward	B-General_Concept
compatibility	I-General_Concept
as	O
possible	O
;	O
but	O
by	O
continuing	O
to	O
use	O
protocols	O
that	O
have	O
known	O
issues	O
,	O
they	O
continue	O
to	O
leave	O
their	O
customers	O
at	O
risk	O
to	O
exploitation	O
...	O
</s>
<s>
To	O
assume	O
that	O
nobody	O
has	O
used	O
this	O
method	O
to	O
exploit	O
people	O
is	O
silly	O
;	O
it	O
took	O
me	O
less	O
than	O
two	O
weeks	O
to	O
write	O
SMBRelay.	O
"	O
</s>
<s>
SMBRelay2	B-Protocol
works	O
at	O
the	O
NetBIOS	B-Protocol
level	O
across	O
any	O
protocol	O
to	O
which	O
NetBIOS	B-Protocol
is	O
bound	O
(	O
such	O
as	O
NBF	B-Protocol
or	O
NBT	O
)	O
.	O
</s>
<s>
It	O
differs	O
from	O
SMBrelay	B-Protocol
in	O
that	O
it	O
uses	O
NetBIOS	B-Protocol
names	O
rather	O
than	O
IP	B-Protocol
addresses	I-Protocol
.	O
</s>
<s>
SMBRelay2	B-Protocol
also	O
supports	O
man-in-the-middling	O
to	O
a	O
third	O
host	O
.	O
</s>
