Slapper signature ??

[Ashley Thomas <athomas () cc gatech edu>]

Hi all,

Snort signature for detecting slapper worm's communication messages is -

alert udp $EXTERNAL_NET 2002 -> $HTTP_SERVERS 2002 (msg:"MISC slapper 
worm admin traffic";
content:"|0000 4500 0045 0000 4000|"; offset:0; depth:10; 
classtype:trojan-activity; 
reference:url,www.cert.org/advisories/CA-2002-27.html;
reference:url,isc.incidents.org/analysis.html?id=167; sid:1889; rev:3;)

Should we be matching for content: "|0000 4500 0045 0000 4000|";
or
content: "|4500 0045 0000 4000|";

I could not understand why the 0000 is there at the starting.

I saw this example on the internet - Notice the 0x0000 which is the part 
of the program
( tcpdump / snoop or whatever ). I hope that is not the 0000 which has 
been included in
the signature. Could anyone please explain ? Thanks a lot.

14:14:23.705193 IP ns.lingv.ro.2002 > xx.yy.116.27.2002: type: 0 chksum: 
be91 id: 6338f02b
tag: 26 id: 7b279513 len: 29 seq: 5c8fa1c1 | route sync=1 hops=5 
server=0 links=11678 [slapper] (DF)

0x0000 4500 0045 0000 4000 2b11 b5e2 c1e6 2582 E..E..@.+.....%.
0x0010 yyxx 741b 07d2 07d2 0031 f1ce 0000 0000 yxt......1......
0x0020 91be 0000 2bf0 3863 2600 0000 1395 277b ....+.8c&.....'{
0x0030 1d00 0000 c1a1 8f5c 0105 0000 0000 0000 .......\........
0x0040 9e2d 0000 00 .-...

Regards,

Ashley



--
Ashley Thomas
Research scientist
College of Computing
Georgia Tech.




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