Snort rules with content

问题

This will generate an alert:

alert tcp any any <> any any (msg:"Test_A"; sid:3000001; rev:1;)

This will not:

alert tcp any any <> any any (msg:"Test_B"; content:"badurl.com"; http_header; sid:3000002; rev:1;)

I have tried: fast_pattern:only; metadata:service http; nocase; http_header; and others. I cannot get it to work at this generic level. Any ideas why the content attribute does not work? The packet has a URL.

Updated from the comments

0000 9c d2 4b 7d 96 60 3c 15 c2 dc 48 fa 08 00 45 00 ..K}.<. ..H...E.
0010 01 5c ac 2c 40 00 40 06 cf f5 c0 a8 c8 1e 41 fe .\.,@.@. ......A. 
0020 f2 b4 dc 41 00 50 d0 e7 97 d0 ae b8 f9 ba 80 18 ...A.P.. ........
0030 ff ff da 1f 00 00 01 01 08 0a 34 03 84 d8 b7 cc ........ ..4.....
0040 3f 04 47 45 54 20 2f 20 48 54 54 50 2f 31 2e 31 ?.GET / HTTP/1.1
0050 0d 0a 48 6f 73 74 3a 20 6d 79 64 6f 6d 61 69 6e ..Host: mydomain 
0060 2e 63 6f 6d 0d 0a 55 73 65 72 2d 41 67 65 6e 74 .com..Us er-Agent

回答1:

The rule that you have provided will never fire with the example packet that you have provided. You have used a content:"POST"; with a http_method modifier but you are attempting to match a packet that is a GET request.

回答2:

I think that the right content modifier should be http_uri, not http_header. Unless you are trying to capture the Host POST parameter.

来源：https://stackoverflow.com/questions/38165145/snort-rules-with-content