alert http $HOME_NET any -> $EXTERNAL_NET any (
msg:"ET MALWARE NORTHSTAR Interactive Client CnC";
flow:established,to_server;
http.method;
content:"GET";
http.uri;
content:"/interact.php?slave="; startswith; fast_pattern;
content:"&sid="; distance:0;
pcre:"/^(?:[A-Za-z0-9+/]{4})*(?:[A-Za-z0-9+/]{2}==|[A-Za-z0-9+/]{3}=|[A-Za-z0-9+/]{4})$/R";
http.referer;
content:"clients.php"; endswith;
reference:url,github.com/EnginDemirbilek/NorthStarC2/;
classtype:command-and-control;
sid:2030190; rev:1;
metadata:attack_target Client_Endpoint, created_at 2020_05_19, deployment Perimeter, performance_impact Low, confidence High, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2020_05_19;
)