alert http $EXTERNAL_NET any -> $HOME_NET any (msg:"ET MALWARE MaskGramStealer Encrypted Data Inbound"; flow:established,to_client; flowbits:isset,ET.MaskGramStealer; http.response_body; content:"encrypted_data|3a 0a|"; startswith; fast_pattern; pcre:"/^(?:[A-Z0-9]{128}\x0a)/R"; reference:md5,5bf89d8f8e9fb53d1e31ff475e987407; classtype:command-and-control; sid:2069170; 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_05_05, deployment Perimeter, deployment SSLDecrypt, malware_family MaskGramStealer, confidence High, signature_severity Critical, tag c2, updated_at 2026_05_05, mitre_tactic_id TA0011, mitre_tactic_name Command_And_Control, mitre_technique_id T1071, mitre_technique_name Application_Layer_Protocol; target:dest_ip;)