alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Cobalt Strike Beacon CnC"; flow:established,to_server; http.method; content:"GET"; http.uri; content:".css"; endswith; http.cookie; content:"lu="; fast_pattern; startswith; pcre:"/^(?:[A-Za-z0-9+/]{4})*(?:[A-Za-z0-9+/]{2}==|[A-Za-z0-9+/]{3}=|[A-Za-z0-9+/]{4})$/R"; http.header_names; content:!"Referer"; reference:md5,ce73caaa42bd465a37802ad3457d2081; reference:url,medium.com/walmartglobaltech/nimar-loader-4f61c090c49e; classtype:command-and-control; sid:2031810; rev:1; metadata:attack_target Client_Endpoint, created_at 2021_03_04, deployment Perimeter, deployment SSLDecrypt, confidence Medium, signature_severity Major, tag c2, updated_at 2021_03_04, mitre_tactic_id TA0010, mitre_tactic_name Exfiltration, mitre_technique_id T1041, mitre_technique_name Exfiltration_Over_C2_Channel;)