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;
)