ET MALWARE Win32/Tofsee Unique Email Body Byte Sequence Observed

alert smtp $HOME_NET any -> $EXTERNAL_NET any (
    msg:"ET MALWARE Win32/Tofsee Unique Email Body Byte Sequence Observed";
    flow:to_server,established;
    content:"|0d 0a 0d 0a 3d 32 30 0d 0a 0d 0a 0d 0a 0d 0a 0d 0a 0d 0a 53 0d 0a|"; fast_pattern;
    threshold:type threshold, count 5, seconds 120, track by_src;
    classtype:command-and-control;
    sid:2029775; rev:2;
    metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, created_at 2020_03_31, malware_family Tofsee, confidence High, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2020_03_31;
)