alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Ransomware/Coverton CnC 2"; flow:to_server,established; http.request_body; content:"task=knock&pub="; fast_pattern; http.header_names; content:!"User-Agent|0d 0a|"; content:!"Referer|0d 0a|"; reference:md5,c5c4f4860c69ea7469ca3be3caf5bf18; classtype:command-and-control; sid:2022678; rev:4; metadata:attack_target Client_Endpoint, created_at 2016_03_28, deployment Perimeter, signature_severity Major, tag Ransomware, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2020_10_05, mitre_tactic_id TA0040, mitre_tactic_name Impact, mitre_technique_id T1486, mitre_technique_name Data_Encrypted_for_Impact;)