alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Win32/MereTam.A Ransomware CnC Init Activity"; flow:established,to_server; http.method; content:"GET"; http.uri; content:"/?gen&session-id="; fast_pattern; pcre:"/^[a-f0-9]{8}-[a-f0-9]{4}-[a-f0-9]{4}-[a-f0-9]{4}-[a-f0-9]{12}$/Rs"; http.header_names; content:!"Accept"; content:!"Cache-"; content:!"Referer"; content:!"User-Agent"; reference:md5,b306115dc9c137b0fa455a9ce1708917; classtype:trojan-activity; sid:2032419; rev:1; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2021_04_05, deployment Perimeter, malware_family Win32_MereTam_A, confidence High, signature_severity Major, tag Ransomware, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2021_04_05, mitre_tactic_id TA0040, mitre_tactic_name Impact, mitre_technique_id T1486, mitre_technique_name Data_Encrypted_for_Impact;)