alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE CastleLoader Task Complete in URI (GET)"; flow:established,to_server; urilen:28; http.method; content:"GET"; http.uri; content:"/service/tasks/complete/id/"; 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; reference:md5,835ab1cf597812b0e6464c2e8f100678; classtype:trojan-activity; sid:2064007; 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 Medium, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2025_08_13; target:src_ip;)