ET MALWARE TA399/Sidewinder Activity Payload Request M1, Microsoft Outlook UA Request for .rtf

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"ET MALWARE TA399/Sidewinder Activity Payload Request M1, Microsoft Outlook UA Request for .rtf";
    flow:established,to_server;
    http.method;
    content:"GET";
    http.uri;
    content:"|2e|rtf"; endswith;
    http.header_names;
    content:!"|0d 0a|Referer|0d 0a|"; nocase;
    http.user_agent;
    content:"Mozilla|2f|4|2e|0|20 28|compatible|3b 20|MSIE|20|7|2e|0|3b 20|Windows|20|NT"; startswith;
    content:"ms|2d|office|3b 20|MSOffice"; distance:0; fast_pattern;
    classtype:command-and-control;
    sid:2055081; rev:5;
    metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, tls_state TLSDecrypt, created_at 2024_08_08, deployment Perimeter, deployment SSLDecrypt, former_category INFO, confidence Medium, signature_severity Major, tag TA399, updated_at 2024_09_26;
)