ET INFO Mailtrack .io Email Activity Tracking M1

Query · suricata

flow:established,to_server;
urilen:66;
http.method;
content:"GET";
http.host;
content:"mailtrack.io"; bsize:12;
http.uri;
content:"/trace/mail/"; startswith; fast_pattern;
pcre:"/^(?:[a-z0-9]{40})\x2epng\x3fu\x3d(?:0-9]{7})$/R";
threshold:type limit, count 1, seconds 1800, track by_src;
Raw source ET INFO Mailtrack .io Email Activity Tracking 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 $HOME_NET any -> $EXTERNAL_NET any (
    msg:"ET INFO Mailtrack .io Email Activity Tracking M1";
    flow:established,to_server;
    urilen:66;
    http.method;
    content:"GET";
    http.host;
    content:"mailtrack.io"; bsize:12;
    http.uri;
    content:"/trace/mail/"; startswith; fast_pattern;
    pcre:"/^(?:[a-z0-9]{40})\x2epng\x3fu\x3d(?:0-9]{7})$/R";
    threshold:type limit, count 1, seconds 1800, track by_src;
    classtype:misc-activity;
    sid:2045062; rev:1;
    metadata:attack_target Client_Endpoint, created_at 2023_04_20, deployment Perimeter, deployment SSLDecrypt, performance_impact Moderate, confidence High, signature_severity Informational, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2023_04_20;
)

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