alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Cobalt Strike Beacon Observed (MASB UA)"; flow:established,to_server; http.method; content:"GET"; http.user_agent; content:"Mozilla/5.0|20|(compatible|3b 20|MSIE 9.0|3b 20|Windows NT|20|6.1|3b 20|WOW64|3b 20|Trident/5.0|3b 20|MASB)"; bsize:76; fast_pattern; http.cookie; pcre:"/^[a-zA-Z0-9/+]{171}=$/"; http.header_names; content:!"Referer"; reference:md5,8079676dd62582da4d2e9d2448c1142d; classtype:command-and-control; sid:2032945; rev:2; metadata:attack_target Client_Endpoint, created_at 2021_05_12, deployment Perimeter, malware_family Cobalt_Strike, confidence Medium, signature_severity Major, tag c2, updated_at 2021_05_12, mitre_tactic_id TA0010, mitre_tactic_name Exfiltration, mitre_technique_id T1041, mitre_technique_name Exfiltration_Over_C2_Channel;)