alert http $HOME_NET any -> any any (msg:"ET MALWARE Win32.Sality-GR Checkin"; flow:established,to_server; http.uri; content:".gif?"; fast_pattern; pcre:"/^[0-9a-f]{4,8}\x3d\x2d?\d+(?:&id\x3d\d+)?$/R"; http.header_names; content:"|0d 0a|User-Agent"; depth:12; content:!"Accept"; content:!"Referer"; reference:md5,3a03a20bfefe3fdd01659d47d2ed76c8; classtype:command-and-control; sid:2018340; rev:12; metadata:created_at 2013_06_07, performance_impact Significant, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2024_04_08;)