alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE MSIL/SkidRat CnC Checkin M1"; flow:established,to_server; http.method; content:"POST"; http.user_agent; content:"Windows|20|NT|20|6,2"; content:"Gecko|2f|201001o1|20|Firef0x/19,0"; distance:0; fast_pattern; http.request_body; content:"9"; depth:1; pcre:"/^9(?:[A-Z0-9+/]{4})*(?:[A-Z0-9+/]{2}==|[A-Z0-9+/]{3}=|[A-Z0-9+/]{4})$/i"; http.header_names; content:!"Referer"; reference:url,www.dodgethissecurity.com/2019/02/28/reverse-engineering-an-unknown-rat-lets-call-it-skidrat-1-0/; classtype:command-and-control; sid:2027057; rev:3; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2019_03_06, deployment Perimeter, malware_family SkidRat, performance_impact Low, confidence High, signature_severity Major, tag RAT, updated_at 2020_08_28;)