ET MALWARE CastleBot CnC Checkin (GET)

Query · suricata

flow:established,to_server;
urilen:82;
http.method;
content:"GET";
http.uri;
content:"/service/settings/"; startswith; fast_pattern;
pcre:"/^[a-z0-9]{64}$/R";
http.header;
content:"cache|2d|control|3a 20|no|2d|cache"; nocase;
content:"pragma|3a 20|no|2d|cache"; nocase;
http.header_names;
content:!"|0d 0a|referer|0d 0a|"; nocase;
target:src_ip;
Raw source ET MALWARE CastleBot CnC Checkin (GET) · 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 -> $EXTERNAL_NET any (
    msg:"ET MALWARE CastleBot CnC Checkin (GET)";
    flow:established,to_server;
    urilen:82;
    http.method;
    content:"GET";
    http.uri;
    content:"/service/settings/"; startswith; fast_pattern;
    pcre:"/^[a-z0-9]{64}$/R";
    http.header;
    content:"cache|2d|control|3a 20|no|2d|cache"; nocase;
    content:"pragma|3a 20|no|2d|cache"; nocase;
    http.header_names;
    content:!"|0d 0a|referer|0d 0a|"; nocase;
    reference:md5,835ab1cf597812b0e6464c2e8f100678;
    classtype:trojan-activity;
    sid:2064004; rev:1;
    metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, tls_state plaintext, created_at 2025_08_13, deployment Perimeter, malware_family CastleBot, confidence High, signature_severity Major, tag c2, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2025_08_13, mitre_tactic_id TA0011, mitre_tactic_name Command_And_Control, mitre_technique_id T1071, mitre_technique_name Application_Layer_Protocol;
    target:src_ip;
)

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