ET HUNTING Suspicious Windows Installer UA for non-MSI

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"ET HUNTING Suspicious Windows Installer UA for non-MSI";
    flow:established,to_server;
    http.method;
    content:"GET";
    http.uri;
    content:!".msi"; endswith;
    http.user_agent;
    content:"Windows Installer"; depth:17; endswith; fast_pattern;
    http.header_names;
    content:!"Referer";
    reference:md5,8000f557f5e8e256b6bd66c82e02aced;
    classtype:policy-violation;
    sid:2038809; rev:4;
    metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2018_09_14, deployment Perimeter, performance_impact Moderate, confidence Medium, signature_severity Major, updated_at 2022_09_13;
)