[Dshield] Re: sdbot variant and WS 55808 activity

Willi Web Willi.Web at mail4web.de
Fri Jun 20 12:25:44 GMT 2003

Some additional info. The mention of "Day 0" might be of concern.


>>> jstewart at lurhq.com 6/18/2003 10:45:08 AM >>>
While researching an IRC zombie infection for a third party, I came
a variant of sdbot which is hard-coded to send TCP packets with a
size of 55808 in its spoofed-synflooding function. Could this be the
"next-gen" trojan that Lancope found? If so, it redefines the term
because sdbot is pretty much old-school.

The particular variant I found is _not_ the well known "sdbot SYN
by Tesla. The packet construction subroutine is entirely different.
Based on
what I have seen here and in the firewall logs from as far back as
I feel that  there is a snippet of C being re-used in the underground
and it
uses a default window size of 55808. I've seen it used in
and now as a synflooder.

Here is an example command used in the IRC control channel to start a 
synflood with this version of sdbot. is the address to be
spoofed while attacking

$syn 6000 20 6666

Here is a capture of some of the resulting packets:

07:26:51.048897 > S
win 55808
0x0000   4500 0028 0a34 0000 8006 ad35 c0a8 0115       
0x0010   c0a8 0101 1a0a 1770 295c 9430 0000 0000       
0x0020   5002 da00 6374 0000 0000 0000 0000             P...ct........

07:26:51.049000 > S 
3950185482:3950185482(0) win 55808
0x0000   4500 0028 0a35 0000 8006 ad34 c0a8 0115       
0x0010   c0a8 0101 1a0a 1770 eb73 0c0a 0000 0000       
0x0020   5002 da00 2983 0000 0000 0000 0000             P...).........

07:26:51.049096 > S 
2692113931:2692113931(0) win 55808
0x0000   4500 0028 0a36 0000 8006 ad33 c0a8 0115       
0x0010   c0a8 0101 1a0a 1770 a076 660b 0000 0000       
0x0020   5002 da00 1a7f 0000 0000 0000 0000             P.............

I have passed the binaries I have found along to the AV community, so 
anti-virus signatures at least for the variants I have found should be

Of course, this still doesn't explain the weird source and destination

IP addresses and ports we are seeing since last month, but based on
this I seriously doubt it is a covert channel. Maybe someone is just 
testing a new implementation of the synscanning code in a distributed 
manner, and has some bugs to work out.


Joe Stewart, GCIH 
Senior Intrusion Analyst
LURHQ Corporation

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