ET INFO Base64 Encoded powershell.exe in HTTP Response M1

Query · suricata

flow:established,from_server;
http.content_type;
content:"text/plain"; startswith;
file.data;
content:"cG93ZXJzaGVsbC5leG"; fast_pattern;
Raw source ET INFO Base64 Encoded powershell.exe in HTTP Response M1 · Suricata
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Published by Emerging Threats Open ↗, licensed under BSD 3-Clause ↗. Line breaks added for readability; the rule is otherwise unchanged. 
alert http $EXTERNAL_NET any -> $HOME_NET any (
    msg:"ET INFO Base64 Encoded powershell.exe in HTTP Response M1";
    flow:established,from_server;
    http.content_type;
    content:"text/plain"; startswith;
    file.data;
    content:"cG93ZXJzaGVsbC5leG"; fast_pattern;
    reference:url,otx.alienvault.com/pulse/5a1348416dd9eb0c92d9897a;
    classtype:bad-unknown;
    sid:2025238; rev:4;
    metadata:created_at 2018_01_22, confidence High, signature_severity Informational, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2020_08_24;
)

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