alert tcp $HOME_NET any -> $EXTERNAL_NET 81 (msg:"ET MALWARE W32/DoubleTap.APT Downloader CnC Beacon"; flow:established,to_server; content:"|05 01 00 01 c0 b8 3c e5 00 51|"; depth:10; reference:url,www.fireeye.com/blog/threat-research/2014/11/operation_doubletap.html; classtype:targeted-activity; sid:2019808; rev:2; metadata:attack_target Client_Endpoint, created_at 2014_11_26, deployment Perimeter, confidence Medium, 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;)