ET MALWARE Ursnif Variant CnC Beacon

Query · suricata

flow:established,to_server;
urilen:>125;
http.method;
content:"GET";
http.uri;
content:"/images/"; fast_pattern;
content:".gif"; distance:100;
pcre:"/\/images(?:\/[a-zA-Z0-9_]+)+\.gif$/";
http.header_names;
content:!"|0d 0a|Accept";
content:!"|0d 0a|Referer|0d 0a|";
http.header;
pcre:"/^User-Agent\x3a\x20(?:Mozilla\/|Shockwave)/mi";
http.user_agent;
content:!"ms-office";
Raw source ET MALWARE Ursnif Variant CnC Beacon · 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 -> $EXTERNAL_NET any (
    msg:"ET MALWARE Ursnif Variant CnC Beacon";
    flow:established,to_server;
    urilen:>125;
    http.method;
    content:"GET";
    http.uri;
    content:"/images/"; fast_pattern;
    content:".gif"; distance:100;
    pcre:"/\/images(?:\/[a-zA-Z0-9_]+)+\.gif$/";
    http.header_names;
    content:!"|0d 0a|Accept";
    content:!"|0d 0a|Referer|0d 0a|";
    http.header;
    pcre:"/^User-Agent\x3a\x20(?:Mozilla\/|Shockwave)/mi";
    http.user_agent;
    content:!"ms-office";
    reference:md5,f48f626cf746a2c3c73182c752c481b6;
    reference:md5,8ab21ac9199d3ced2230924b90f49f0d;
    classtype:command-and-control;
    sid:2021813; rev:10;
    metadata:attack_target Client_Endpoint, created_at 2015_09_23, deployment Perimeter, performance_impact Significant, signature_severity Major, tag c2, updated_at 2024_04_29, mitre_tactic_id TA0010, mitre_tactic_name Exfiltration, mitre_technique_id T1041, mitre_technique_name Exfiltration_Over_C2_Channel;
)

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