alert smtp $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Win32/MALWARECAT Exfil via SMTP"; flow:established,to_server; content:"Subject|3a 20|MALWARECAT"; fast_pattern; reference:md5,bc45f9e3b0a681fb7bc08dbf3c44bcf3; classtype:command-and-control; sid:2032271; rev:2; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2021_03_22, deployment Perimeter, malware_family Win32_MALWARECAT, confidence High, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2021_03_22;)