alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Locky CnC Checkin Dec 5 M1"; flow:to_server,established; urilen:12; http.method; content:"POST"; http.uri; content:"/checkupdate"; fast_pattern; http.header; content:"x-requested-with|3a 20|XMLHttpRequest|0d 0a|"; content:"www-form-urlencoded|0d 0a|"; http.request_body; pcre:"/^(?:[A-Za-z]{1,10}=(?=[A-Za-z0-9_+\x2d\x2e%]*%[A-F0-9]{2}%[A-F0-9]{2}%[A-F0-9]{2})[A-Za-z0-9_+\x2d\x2e%]+&)+(?=[a-z]{0,9}[A-Z])(?=[A-Z]{0,9}[a-z])[A-Za-z]{1,10}=(?=[A-Za-z0-9_+\x2d\x2e%]*%[A-F0-9]{2}%[A-F0-9]{2}%[A-F0-9]{2})[A-Za-z0-9_+\x2d\x2e%]+\s*$/s"; classtype:command-and-control; sid:2023576; rev:6; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2016_12_05, deployment Perimeter, malware_family Locky, performance_impact Low, confidence High, signature_severity Major, updated_at 2020_11_04;)