alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Cobalt Strike CnC Activity"; flow:established,to_server; http.method; content:"GET"; http.uri; content:"/mt?"; startswith; fast_pattern; content:"="; distance:0; http.cookie; content:"lu="; startswith; pcre:"/^(?:[A-Za-z0-9+/]{4})*(?:[A-Za-z0-9+/]{2}==|[A-Za-z0-9+/]{3}=|[A-Za-z0-9+/]{4})$/R"; reference:md5,0d2c5bbf711058f31cd8ce81da30e870; reference:url,medium.com/walmartglobaltech/nimar-loader-4f61c090c49e; classtype:command-and-control; sid:2031806; rev:1; metadata:attack_target Client_Endpoint, created_at 2021_03_03, deployment Perimeter, deployment SSLDecrypt, performance_impact Low, confidence Medium, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2021_03_03;)