ET MALWARE CastleLoader Malware Outbound Checkin

Query · suricata

flow:established,to_server;
urilen:82;
http.method;
content:"GET";
http.uri;
content:"|2F|service|2F|settings|2F|"; fast_pattern;
http.header;
content:"cache-control|3d 20|no-cache|0d 0a|connection|3a 20|keep-alive|0d 0a|pragma|3a 20|no-cache|0d 0a|user-agent|3a 20 0d 0a|";
content:"host|3a 20|"; distance:0;
content:!"accept|3a 20|"; nocase;
target:dest_ip;
Raw source ET MALWARE CastleLoader Malware Outbound Checkin · 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 $HOME_NET any -> $EXTERNAL_NET any (
    msg:"ET MALWARE CastleLoader Malware Outbound Checkin";
    flow:established,to_server;
    urilen:82;
    http.method;
    content:"GET";
    http.uri;
    content:"|2F|service|2F|settings|2F|"; fast_pattern;
    http.header;
    content:"cache-control|3d 20|no-cache|0d 0a|connection|3a 20|keep-alive|0d 0a|pragma|3a 20|no-cache|0d 0a|user-agent|3a 20 0d 0a|";
    content:"host|3a 20|"; distance:0;
    content:!"accept|3a 20|"; nocase;
    reference:url,catalyst.prodaft.com/public/report/understanding-current-castleloader-campaigns/overview;
    classtype:trojan-activity;
    sid:2066299; rev:1;
    metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, affected_product Mac_OSX, attack_target Client_Endpoint, tls_state TLSDecrypt, created_at 2025_12_12, deployment Perimeter, deployment SSLDecrypt, malware_family CastleLoader, performance_impact Moderate, confidence Medium, signature_severity Major, updated_at 2025_12_12, mitre_tactic_id TA0011, mitre_tactic_name Command_And_Control, mitre_technique_id T1041, mitre_technique_name Exfiltration_Over_C2_Channel;
    target:dest_ip;
)

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