ET INFO Certificate with Unknown Content M1

Query · suricata

flow:established,to_client;
file_data;
content:"-----BEGIN CERTIFICATE-----|0D 0A|"; depth:29; fast_pattern;
byte_test:1,!=,0x4D,0,relative;
Raw source ET INFO Certificate with Unknown Content M1 · Suricata
Esc
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 Certificate with Unknown Content M1";
    flow:established,to_client;
    file_data;
    content:"-----BEGIN CERTIFICATE-----|0D 0A|"; depth:29; fast_pattern;
    byte_test:1,!=,0x4D,0,relative;
    reference:url,blog.nviso.be/2018/07/31/powershell-inside-a-certificate-part-1/;
    classtype:misc-activity;
    sid:2026649; rev:2;
    metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2018_11_26, deployment Perimeter, performance_impact Moderate, confidence Medium, signature_severity Major, updated_at 2019_07_26;
)

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