ET MALWARE CastleLoader Malware Inbound Command Retrieval via Finger Service

alert tcp $EXTERNAL_NET 79 -> $HOME_NET any (
    msg:"ET MALWARE CastleLoader Malware Inbound Command Retrieval via Finger Service";
    flow:established,to_client;
    content:"Login|3A 20|"; depth:7;
    content:"Plan|3A|"; distance:0;
    content:"%random%"; fast_pattern; distance:0;
    content:"|20|--tlsv1.2|20|-L|20|-o|20|"; distance:0;
    content:"|0D 0A|mkdir|20|"; distance:0;
    content:"|0D 0A|tar|20|"; distance:0;
    reference:url,tria.ge/251110-zcgvkstpck;
    reference:url,assets.recordedfuture.com/insikt-report-pdfs/2025/cta-2025-1209.pdf;
    classtype:trojan-activity;
    sid:2066355; 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_17, deployment Perimeter, deployment SSLDecrypt, malware_family CastleLoader, performance_impact Moderate, confidence Medium, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2025_12_17, mitre_tactic_id TA0011, mitre_tactic_name Command_And_Control, mitre_technique_id T1041, mitre_technique_name Exfiltration_Over_C2_Channel;
    target:dest_ip;
)