alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE ShadowLink IoT Botnet CnC Checkin Attempt M1 (Asus Variant)"; flow:established,to_server; http.method; content:"POST"; http.uri; bsize:5; content:"/b/in"; http.header; content:"X-B|3a 20|"; fast_pattern; http.request_body; content:"|22|h|22|"; content:"|22|u|22|"; content:"|22|root|22|"; within:10; content:"|22|o|22|"; content:"|22|ASUSWRT"; within:15; reference:url,ctrlaltintel.com/research/ProxyPCP/; classtype:trojan-activity; sid:2068764; rev:1; metadata:affected_product IoT, attack_target Networking_Equipment, tls_state TLSDecrypt, created_at 2026_04_14, deployment Perimeter, deployment SSLDecrypt, malware_family ShadowLink, 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;)