alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE FrigidBackdoor Health Check"; flow:established,to_server; http.method; content:"POST"; http.uri; bsize:11; content:"/api/health"; http.user_agent; content:"curl/"; startswith; http.header; content:"X-Bid: f48fbe39836779cadbf148b5952919fd"; fast_pattern; reference:url,moonlock.com/macc-stealer-macsync-backdoor; classtype:trojan-activity; sid:2064776; rev:1; metadata:affected_product Mac_OSX, attack_target Client_Endpoint, tls_state TLSDecrypt, created_at 2025_09_18, deployment Perimeter, confidence High, signature_severity Major, tag Backdoor, tag c2, tag Description_Generated_By_Proofpoint_Nexus, tag FrigidBackdoor, updated_at 2025_09_18, mitre_tactic_id TA0011, mitre_tactic_name Command_And_Control, mitre_technique_id T1071, mitre_technique_name Application_Layer_Protocol;)