ET MALWARE CastleLoader Bot Download (GET)

Query · suricata

flow:established,to_server;
http.method;
content:"GET";
http.uri;
content:"/service/download/"; startswith; fast_pattern;
pcre:"/\x2e(?:exe|bin|zip|msi|docx?|msi|xlsx?|dll)$/";
http.header_names;
content:!"|0d 0a|referer|0d 0a|"; nocase;
target:src_ip;
Raw source ET MALWARE CastleLoader Bot Download (GET) · 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 -> $EXTERNAL_NET any (
    msg:"ET MALWARE CastleLoader Bot Download (GET)";
    flow:established,to_server;
    http.method;
    content:"GET";
    http.uri;
    content:"/service/download/"; startswith; fast_pattern;
    pcre:"/\x2e(?:exe|bin|zip|msi|docx?|msi|xlsx?|dll)$/";
    http.header_names;
    content:!"|0d 0a|referer|0d 0a|"; nocase;
    reference:md5,1a3896a986195c277f1547706dbdea08;
    reference:md5,f75bb2393f80bf30c4788c82f3a7dadf;
    reference:url,ibm.com/think/x-force/dissecting-castlebot-maas-operation;
    classtype:trojan-activity;
    sid:2064197; rev:1;
    metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, tls_state TLSDecrypt, created_at 2025_08_28, deployment Perimeter, deployment SSLDecrypt, malware_family CastleLoader, confidence Medium, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2025_08_28, mitre_tactic_id TA0011, mitre_tactic_name Command_And_Control, mitre_technique_id T1105, mitre_technique_name Ingress_Tool_Transfer;
    target:src_ip;
)

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