alert tcp $HOME_NET any -> $EXTERNAL_NET $HTTP_PORTS (msg:"ET MALWARE BarACE? Checkin and Update"; flow:established,to_server; content:"GET "; depth:4; uricontent:"|2E|php|3F|zone="; nocase; content:"|26|name="; nocase; content:"|26|bpid="; nocase; content:"|26|bnum="; nocase; content:"|26|pid="; nocase; reference:url,www.symantec.com/security_response/writeup.jsp?docid=2007-021714-2431-99&tabid=2; classtype:trojan-activity; sid:2008505; rev:1;)

Added 2008-08-12 12:45:21 UTC

Sample: (this is not 100% confirmed but it sure matches the pattern).

GET /logonmuz/adexp.php?zone=app&name=ebiz&bpid=divxfree&bnu m=divxfree_inst&pid=divxfree HTTP/1.1..Host: log.onmuz.com.. Cache-Control: no-cache..

-- RussellFulton - 24 Nov 2008