alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE MaskGramStealer Host Screenshot Exfil (POST)"; flow:established,to_server; http.method; content:"POST"; http.user_agent; bsize:10; content:"Client/1.0"; http.header; content:"X|2d|Filename|3a 20|screenshot|2e|bmp|0d 0a|"; fast_pattern; http.request_body; content:"BM"; startswith; reference:md5,25041e230c55fd46e5ef52ab02b3bc6c; classtype:command-and-control; sid:2066631; rev:2; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, tls_state TLSDecrypt, created_at 2026_01_08, deployment Perimeter, deployment SSLDecrypt, malware_family MaskGramStealer, confidence High, signature_severity Critical, tag Description_Generated_By_Proofpoint_Nexus, 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:src_ip;)