[Snort-sigs] Have I lost my mind?

Todd Wease twease at ...435...
Wed Jan 13 16:06:58 EST 2010


On 01/13/2010 11:29 AM, Paul Schmehl wrote:
> 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?
>
>    

Most likely the issue is that you're specifying uricontent, when the 
contents are actually in the header.  You should rather specify:

content:"Server: gws"; http_header;

etc.






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