alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Unknown Mailer CnC Beacon"; flow:established,to_server; http.method; content:"GET"; http.uri; content:"/action.php?action=get_"; fast_pattern; pcre:"/^\/action\.php\?action=get_(?:mails|red)$/"; http.user_agent; content:"Send Mail"; depth:9; http.header_names; content:!"Referer|0d 0a|"; reference:md5,57e546330fd3a4658dff0e29cbb98214; classtype:command-and-control; sid:2020330; rev:4; metadata:attack_target Client_Endpoint, created_at 2015_01_29, deployment Perimeter, confidence Medium, signature_severity Major, tag c2, updated_at 2020_09_29, mitre_tactic_id TA0010, mitre_tactic_name Exfiltration, mitre_technique_id T1041, mitre_technique_name Exfiltration_Over_C2_Channel;)