alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE CastleLoader CnC Exfil (POST)"; flow:established,to_server; urilen:14; http.method; content:"POST"; http.uri; content:"/service/tasks"; fast_pattern; http.header; content:"cache|2d|control|3a 20|no|2d|cache"; nocase; content:"pragma|3a 20|no|2d|cache"; nocase; http.header_names; content:!"|0d 0a|referer|0d 0a|"; nocase; http.request_body; content:"Content|2d|Disposition|3a 20|form|2d|data|3b 20|name|3d 22|data|22|"; http.content_type; content:"HttpClient"; reference:md5,835ab1cf597812b0e6464c2e8f100678; classtype:trojan-activity; sid:2064005; rev:1; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, tls_state plaintext, created_at 2025_08_13, deployment Perimeter, malware_family CastleLoader, confidence High, signature_severity Major, tag c2, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2025_08_13, mitre_tactic_id TA0011, mitre_tactic_name Command_And_Control, mitre_technique_id T1071, mitre_technique_name Application_Layer_Protocol; target:src_ip;)