alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE APT Backspace CnC Beacon"; flow:to_server,established; http.method; content:"POST"; http.header; content:"HOST|3a 20|"; http.user_agent; content:"SJZJ (compatible|3b 20|MSIE 6.0|3b 20|Win32)"; fast_pattern; startswith; http.header_names; content:!"Accept"; content:!"Referer|0d 0a|"; reference:md5,ddf0981aebeea6ba9abdae6ddf8ed4e2; classtype:targeted-activity; sid:2021184; rev:4; metadata:attack_target Client_Endpoint, created_at 2015_06_05, deployment Perimeter, signature_severity Major, tag c2, updated_at 2020_10_01, mitre_tactic_id TA0010, mitre_tactic_name Exfiltration, mitre_technique_id T1041, mitre_technique_name Exfiltration_Over_C2_Channel;)