[Snort-sigs] Help with a signature

Wilson, Dave Dave.Wilson at ...3732...
Fri Sep 14 09:06:09 EDT 2012


Hello,

I'm trying to create a snort rule that will alert on traffic that contains "rfihub" as part of the url.  Here is an example of the TCP stream of a packet that I'd want to alert on.

00000000  47 45 54 20 2f 63 6d 3f  70 69 64 3d 32 30 37 36        GET /cm? pid=2076
00000010  32 35 30 66 2d 39 32 63  32 2d 34 65 63 64 2d 39      250f-92c 2-4ecd-9
00000020  30 34 33 2d 63 63 36 33  65 65 36 63 34 35 37 37      043-cc63 ee6c4577
00000030  26 64 73 74 3d 68 74 74  70 25 33 41 25 32 46 25      &dst=htt p%3A%2F%
00000040  32 46 70 2e 72 66 69 68  75 62 2e 63 6f 6d 25 32       2Fp.rfih ub.com%2
00000050  46 63 6d 25 33 46 69 6e                                               Fcm%3Fin
00000058  5b 31 32 37 32 20 62 79  74 65 73 20 6d 69 73 73      [1272 by tes miss
00000068  69 6e 67 20 69 6e 20 63  61 70 74 75 72 65 20 66      ing in c apture f
00000078  69 6c 65 5d                                                                      ile]
0000007C  61 74 68 65 72 2e 63 6f  6d 25 32 46 6d 61 6e 61      ather.co m%2Fmana
0000008C  67 65 64 66 65 25 32 46  6d 61 6b 65 52 65 71 75     gedfe%2F makeRequ
0000009C  65 73 74 2d 6d 61 78 2e  68 74 6d 6c 25 33 46 70     est-max. html%3Fp
000000AC  6f 73 25 33 44 57 58 5f  54 6f 70 33 30 30 56 61       os%3DWX_ Top300Va
000000BC  72 69 61 62 6c 65 26 70  66 3d 0d 0a 43 6f 6f 6b       riable&p f=..Cook
000000CC  69 65 3a 20 69 3d 65 31                                            ie: i=e1
00000000  48 54 54 50 2f 31 2e 31  20 33 30 32 20 4f 4b 0d        HTTP/1.1  302 OK.
00000010  0a 43 6f 6e 74 65 6e 74  2d 54 79 70 65 3a 20 74       .Content -Type: t
00000020  65 78 74 2f 68 74 6d 6c  3b 20 63 68 61 72 73 65       ext/html ; charse
00000030  74 3d 75 74 66 2d 38 0d  0a 50 33 50 3a 20 43 50      t=utf-8. .P3P: CP
00000040  3d 22 43 55 52 20 41 44  4d 20 4f 55 52 20 4e 4f        ="CUR AD M OUR NO
00000050  52 20 53 54 41 20 4e 49                                            R STA NI


Here is the rule I put together:


alert tcp any any -> any any (msg:"Zeroaccess variant"; content:"|72 66 69 68 75 62|" sid:1000001;)


When feed the pcap into snort, It'll process it, but not alert.  I've tried changing the protocol from tcp to http, but snort chokes and tells me "Bad Protocol: http"

I'm still very new at writing snort rules, so I apologize in advance for any helpful details I've left out.  I really appreciate any assistance...thank you.

Dave
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