alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE BalkanDoor CnC Checkin"; flow:established,to_server; http.method; content:"GET"; http.uri; content:".php?s="; fast_pattern; content:"&cn="; pcre:"/\.php\?s=\d+&cn=/"; http.header_names; content:!"|0d 0a|Referer|0d 0a|"; reference:url,www.welivesecurity.com/2019/08/14/balkans-businesses-double-barreled-weapon/; reference:md5,f70ef75fb0a51b05c43aaec973ac0bc1; classtype:command-and-control; sid:2027897; rev:2; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2019_08_19, deployment Perimeter, performance_impact Low, confidence High, signature_severity Major, updated_at 2020_09_01;)