[Snort-sigs] Have I lost my mind?

Paul Schmehl pschmehl_lists at ...3425...
Wed Jan 13 11:29:16 EST 2010


I wrote a rule to see what a certain host was up to:

alert tcp 95.211.27.211 any -> $HOME_NET any (msg:"Up to no good?"; 
classtype:web-application-activity; sid:1000174; re
v:1;)

That produced (among others) this packet:

000 : 48 54 54 50 2F 31 2E 31 20 32 30 30 20 4F 4B 0D   HTTP/1.1 200 OK.
010 : 0A 53 65 72 76 65 72 3A 20 67 77 73 0D 0A 44 61   .Server: gws..Da
020 : 74 65 3A 20 54 75 65 2C 20 31 32 20 4A 61 6E 20   te: Tue, 12 Jan
030 : 32 30 31 30 20 30 36 3A 34 35 3A 30 38 20 47 4D   2010 06:45:08 GM
040 : 54 0D 0A 43 6F 6E 74 65 6E 74 2D 54 79 70 65 3A   T..Content-Type:
050 : 20 74 65 78 74 2F 68 74 6D 6C 0D 0A 43 6F 6E 6E    text/html..Conn
060 : 65 63 74 69 6F 6E 3A 20 63 6C 6F 73 65 0D 0A 58   ection: close..X
070 : 2D 50 6F 77 65 72 65 64 2D 42 79 3A 20 50 48 50   -Powered-By: PHP
080 : 2F 35 2E 32 2E 36 2D 31 2B 6C 65 6E 6E 79 34 0D   /5.2.6-1+lenny4.
090 : 0A 43 6F 6E 74 65 6E 74 2D 4C 65 6E 67 74 68 3A   .Content-Length:
0a0 : 20 31 32 30 0D 0A 0D 0A 33 43 33 45 37 41 36 45    120....3C3E7A6E
0b0 : 36 38 32 35 37 30 36 32 37 41 37 41 36 33 36 34   682570627A7A6364
0c0 : 36 32 33 30 32 43 33 45 33 45 32 31 33 30 33 33   62302C3E3E213033
0d0 : 37 31 37 42 37 35 37 38 37 43 37 30 37 34 37 43   717B75787C70747C
0e0 : 32 31 33 46 36 42 36 42 34 36 30 43 31 41 30 31   213F6B6B460C1A01
0f0 : 31 42 31 42 32 43 31 42 35 30 34 34 34 36 34 46   1B1B2C1B5044464F
100 : 34 44 35 39 34 46 31 31 33 41 30 44 31 44 34 42   4D594F113A0D1D4B
110 : 35 39 35 39 35 32 35 36 34 43 35 38 30 34 33 31   595952564C580431

Source address is 95.211.27.211.  Source port is 80.

So I wrote this rule:

alert tcp $EXTERNAL_NET 80 -> $HOME_NET any (msg:"Bredolab server ack"; 
flow:from_server,established; content:"Server: gws"; content:"X-Powered-By: P
HP"; content:"+lenny4"; classtype:trojan-activity; sid:1000172; rev:1;)

But it never triggered (even though the first rule continues to).  So I altered 
it thus:

alert tcp $EXTERNAL_NET 80 -> $HOME_NET any (msg:"Bredolab server ack"; 
flow:from_server,established; uricontent:"Server: gws"; 
uricontent:"X-Powered-By: P
HP"; uricontent:"+lenny4"; classtype:trojan-activity; sid:1000172; rev:2;)

But it still didn't trigger, so I altered it again:

alert tcp $EXTERNAL_NET 80 -> $HOME_NET any (msg:"Bredolab server ack"; 
uricontent:"Server: gws"; uricontent:"X-Powered-By: PHP"; uricontent:"+lenny4"; 
classtype:trojan-activity; sid:1000172; rev:3;)

But it still didn't trigger, so I altered it yet again:

alert tcp $EXTERNAL_NET 80 -> $HOME_NET any (msg:"Bredolab server ack"; 
content:"Server: gws"; content:"X-Powered-By: PHP"; content:"+lenny4"; 
classtype:trojan-activity; sid:1000172; rev:4;)

It still doesn't trigger.

Someone please enlighten me.  What am I missing?

-- 
Paul Schmehl, Senior Infosec Analyst
As if it wasn't already obvious, my opinions
are my own and not those of my employer.
*******************************************
"It is as useless to argue with those who have
renounced the use of reason as to administer
medication to the dead." Thomas Jefferson





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