ET USER_AGENTS Suspicious User Agent (agent)

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"ET USER_AGENTS Suspicious User Agent (agent)";
    flow:established,to_server;
    http.header;
    content:!"cn.patch.battlenet.com.cn";
    http.user_agent;
    content:"agent"; fast_pattern; startswith;
    http.host;
    content:!".battle.net"; endswith;
    content:!".blizzard.com"; endswith;
    content:!"blz"; depth:3;
    content:!".acronis.com"; endswith;
    classtype:trojan-activity;
    sid:2001891; rev:25;
    metadata:tls_state plaintext, created_at 2010_07_30, deployment Perimeter, deployment Internal, performance_impact Low, confidence High, signature_severity Major, updated_at 2025_07_31;
    target:src_ip;
)