alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Win32/RCAP CnC Checkin"; flow:established,to_server; http.method; content:"GET"; http.uri; content:"/callback.php?k="; fast_pattern; content:"&x="; distance:0; http.connection; content:"close"; bsize:5; http.header_names; content:!"Referer|0d 0a|"; reference:md5,3410af519f791af5f9554cbff7ece24a; classtype:command-and-control; sid:2024984; rev:3; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2017_11_14, deployment Perimeter, malware_family Win32_RCAP, performance_impact Moderate, confidence High, signature_severity Major, updated_at 2020_08_17;)