alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE W32/LetsGo.APT Sleep CnC Beacon"; flow:established,to_server; http.uri; pcre:"/\.html\?[0-9]{10}$/"; http.user_agent; content:"sleep|20|"; fast_pattern; startswith; pcre:"/^sleep \d+[\r\x2c]/"; reference:url,www.fireeye.com/blog/technical/targeted-attack/2013/03/the-dingo-and-the-baby.html; classtype:targeted-activity; sid:2016568; rev:4; metadata:attack_target Client_Endpoint, created_at 2013_03_14, deployment Perimeter, signature_severity Major, tag c2, updated_at 2020_09_18, mitre_tactic_id TA0010, mitre_tactic_name Exfiltration, mitre_technique_id T1041, mitre_technique_name Exfiltration_Over_C2_Channel;)