alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE NORTHSTAR Client CnC Checkin"; flow:established,to_server; http.method; content:"GET"; http.uri; content:"/smanage.php?sid="; startswith; fast_pattern; pcre:"/^(?:[A-Za-z0-9+/]{4})*(?:[A-Za-z0-9+/]{2}==|[A-Za-z0-9+/]{3}=|[A-Za-z0-9+/]{4})$/R"; http.header_names; content:!"Referer"; content:!"User-Agent"; reference:url,github.com/EnginDemirbilek/NorthStarC2/; classtype:command-and-control; sid:2030188; 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;)