alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE StealC CnC Activity (POST)"; flow:established,to_server; urilen:21; http.method; content:"POST"; http.uri; pcre:"/^\x2f[a-z0-9]{16}\x2ephp$/"; http.content_type; content:"application/json"; http.connection; content:"Keep-Alive"; http.header; content:"Cache|2d|Control|3a 20|no|2d|cache|0d 0a|"; http.header_names; bsize:67; content:"|0d 0a|content-type|0d 0a|host|0d 0a|content-length|0d 0a|connection|0d 0a|cache-control|0d 0a 0d 0a|"; nocase; fast_pattern; threshold:type limit,count 1,seconds 300,track by_src; classtype:command-and-control; sid:2066559; rev:1; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, tls_state TLSDecrypt, created_at 2026_01_02, deployment Perimeter, deployment SSLDecrypt, malware_family Stealc, confidence High, signature_severity Critical, tag c2, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2026_01_02, mitre_tactic_id TA0011, mitre_tactic_name Command_And_Control, mitre_technique_id T1071, mitre_technique_name Application_Layer_Protocol; target:src_ip;)