ET MALWARE CastleBot CnC Checkin - Task Complete

Query · suricata

flow:established,to_server;
urilen:<30;
http.method;
content:"GET";
http.uri;
content:"/service/tasks/complete/id/"; startswith; fast_pattern;
pcre:"/^\d{1,3}$/R";
http.user_agent; bsize:<26;
pcre:"/^(?:[a-zA-Z0-9]{20,25})$/";
target:src_ip;
Raw source ET MALWARE CastleBot CnC Checkin - Task Complete · 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 -> $EXTERNAL_NET any (
    msg:"ET MALWARE CastleBot CnC Checkin - Task Complete";
    flow:established,to_server;
    urilen:<30;
    http.method;
    content:"GET";
    http.uri;
    content:"/service/tasks/complete/id/"; startswith; fast_pattern;
    pcre:"/^\d{1,3}$/R";
    http.user_agent; bsize:<26;
    pcre:"/^(?:[a-zA-Z0-9]{20,25})$/";
    reference:md5,1a3896a986195c277f1547706dbdea08;
    reference:md5,f75bb2393f80bf30c4788c82f3a7dadf;
    reference:url,ibm.com/think/x-force/dissecting-castlebot-maas-operation;
    classtype:trojan-activity;
    sid:2064207; 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 CastleBot, confidence High, signature_severity Critical, tag c2, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2025_08_28, mitre_tactic_id TA0011, mitre_tactic_name Command_And_Control, mitre_technique_id T1071, mitre_technique_name Application_Layer_Protocol;
    target:src_ip;
)

Detection rules belong to the projects that publish them and remain under their own licenses. This site indexes and links to them; it claims no rights in them.