#alert tcp $HOME_NET any -> $EXTERNAL_NET $HTTP_PORTS (msg:"BLEEDING-EDGE VIRUS webstats.web.rcn.net count.cgi request without referrer (possible BlackWorm?/Nyxem infection)"; flow:to_server,established; content:"GET /cgi-bin/Count.cgi?"; depth:23; content:"df="; within:20; content:"Host|3a 20|webstats.web.rcn.net"; content:!"Referer|3a|"; classtype:misc-activity; sid:2002788; rev:3;)