alert http $EXTERNAL_NET any -> $HOME_NET any (msg:"ET MALWARE CozyDuke APT HTTP CnC Beacon Response"; flow:established,from_server; file_data; content:"<--"; within:3; pcre:"/^[A-F0-9]{8,12}/R"; content:"-->|0a|<"; fast_pattern; within:5; flowbits:isset,ET.CozyDuke.HTTP; reference:url,securelist.com/blog/69731/the-cozyduke-apt/; reference:md5,98a6484533fa12a9ba6b1bd9df1899dc; classtype:targeted-activity; sid:2020965; rev:2; metadata:attack_target Client_Endpoint, created_at 2015_04_22, deployment Perimeter, signature_severity Major, tag c2, updated_at 2019_07_26, mitre_tactic_id TA0010, mitre_tactic_name Exfiltration, mitre_technique_id T1041, mitre_technique_name Exfiltration_Over_C2_Channel;)