alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE APT28 SEDNIT Variant CnC Beacon 4"; flow:to_server,established; http.method; content:"POST"; http.uri; content:".xml/?"; fast_pattern; pcre:"/\.xml\/\?[A-Za-z0-9]+=(?:[A-Za-z0-9+/]{4})*(?:[A-Za-z0-9+/]{2}==|[A-Za-z0-9+/]{3}=|[A-Za-z0-9+/]{4})$/"; http.header_names; content:!"Content-Type|0d 0a|"; content:!"Accept"; content:!"Referer|0d 0a|"; reference:md5,c2988e3e4f70d5901b234ff1c1363dcc; classtype:targeted-activity; sid:2023915; rev:4; metadata:attack_target Client_Endpoint, created_at 2016_06_09, deployment Perimeter, confidence High, signature_severity Major, tag c2, updated_at 2020_10_06, mitre_tactic_id TA0010, mitre_tactic_name Exfiltration, mitre_technique_id T1041, mitre_technique_name Exfiltration_Over_C2_Channel;)