alert tcp $HOME_NET any -> $EXTERNAL_NET 443 (msg:"ET MALWARE APT Lurker GET CnC Beacon"; flow:established,to_server; content:"GET /"; depth:5; content:".php HTTP/1."; distance:0; fast_pattern; content:!"Accept"; distance:0; content:!"Referer|3a|"; distance:0; content:"HOST|3a|"; distance:3; within:5; pcre:"/^[^\r\n]+\r\nUser-Agent\x3a[^\r\n]+\r\n(?:\r\n)?$/Rmi"; reference:md5,c5a8e09295b852a6e32186374b66e1a7; reference:url,blogs.rsa.com/wp-content/uploads/2015/05/RSA-IR-Case-Study.pdf; classtype:targeted-activity; sid:2021585; rev:3; metadata:attack_target Client_Endpoint, created_at 2015_08_03, 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;)