[Snort-sigs] Have I lost my mind?

Todd Wease twease at ...435...
Wed Jan 13 16:09:59 EST 2010


You do not need to escape a colon in a content.


On 01/13/2010 02:48 PM, Paul Schmehl wrote:
> I always run snort -T -c /blah/foo/snort.conf after writing a new rule or
> altering an existing rule.  Snort was running happily along without a complaint
> with the colons not escaped.  (It also doesn't complain when they *are*
> escaped, but that would be expected behavior.)
>
> --On Wednesday, January 13, 2010 12:24:07 -0600 Joel Esler
> <jesler at ...435...>  wrote:
>
>    
>> Did you run Snort in -T and see if it chokes on it?
>>
>>
>> J
>>
>>
>> On Wed, Jan 13, 2010 at 1:02 PM, Paul Schmehl<pschmehl_lists at ...3425...>
>> wrote:
>>
>> Doh.  Wonder why snort didn't choke on that and throw an error?
>>
>>
>>
>>
>> --On Wednesday, January 13, 2010 11:13:03 -0600 Joel Esler
>> <jesler at ...435...>  wrote:
>>
>>
>>
>> You didn't escape the colon in "X-Powered-By:" ?
>>
>> At first glance.
>>
>> J
>>
>> On Jan 13, 2010, at 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?
>>
>> --
>> 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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>>
>>
>>
>>
>> --
>> 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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