alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE CNRarypt Ransomware CnC Activity"; flow:established,to_server; http.method; content:"GET"; http.uri; content:"/HOW_TO_BACK_YOUR_FILES.txt"; endswith; fast_pattern; http.user_agent; content:"CertUtil URL Agent"; bsize:18; http.header_names; content:!"Referer"; reference:md5,62292df897bf304872aad2dc92c96d70; classtype:trojan-activity; sid:2033075; rev:1; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2021_06_03, deployment Perimeter, confidence High, signature_severity Major, tag Ransomware, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2021_06_03, mitre_tactic_id TA0040, mitre_tactic_name Impact, mitre_technique_id T1486, mitre_technique_name Data_Encrypted_for_Impact;)