ET MALWARE JS/Unk Downloader 0 Byte POST CnC Checkin

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"ET MALWARE JS/Unk Downloader 0 Byte POST CnC Checkin";
    flow:established,to_server;
    http.method;
    content:"POST";
    http.header;
    content:"Content-Length|3a 20|0|0d|";
    http.user_agent;
    content:"xmsSofts_1.0.0_"; depth:15; fast_pattern;
    content:"|5c|"; endswith;
    http.header_names;
    content:!"Referer";
    classtype:command-and-control;
    sid:2026760; rev:4;
    metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2019_01_07, deployment Perimeter, performance_impact Low, confidence High, signature_severity Major, tag Downloader, tag JavaScript, updated_at 2022_03_24;
)