alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE ShadowLink IoT Botnet Socks Proxy Registration Attempt"; flow:established,to_server; http.method; content:"GET"; http.uri; content:"/reg|3f|ip|3d|"; startswith; fast_pattern; pcre:"/^(?:\d{1,3}\x2e){3}\d{1,3}/R"; content:"|26|port|3d|"; pcre:"/^\d{1,5}$/R"; reference:url,ctrlaltintel.com/research/ProxyPCP/; classtype:trojan-activity; sid:2068765; rev:1; metadata:affected_product IoT, attack_target Networking_Equipment, tls_state plaintext, created_at 2026_04_14, deployment Perimeter, malware_family ShadowLink, performance_impact Low, confidence High, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2026_04_14, mitre_tactic_id TA0037, mitre_tactic_name Command_And_Control, mitre_technique_id T1041, mitre_technique_name Exfiltration_Over_C2_Channel; target:src_ip;)