ET INFO kcptun Null Encryption Message Header

Query · suricata

flow:stateless,to_server;
content:"|51 00 00 02|"; fast_pattern; offset:32; depth:4;
content:"|01 02|"; within:20;
content:"|03|"; within:4;
Raw source ET INFO kcptun Null Encryption Message Header · 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 udp $HOME_NET any -> $EXTERNAL_NET any (
    msg:"ET INFO kcptun Null Encryption Message Header";
    flow:stateless,to_server;
    content:"|51 00 00 02|"; fast_pattern; offset:32; depth:4;
    content:"|01 02|"; within:20;
    content:"|03|"; within:4;
    reference:url,github.com/sspanel/kcptun;
    reference:url,github.com/nebulabox/kcptun;
    classtype:misc-activity;
    sid:2072396; rev:1;
    metadata:affected_product Any, attack_target Client_and_Server, tls_state plaintext, created_at 2026_10_08, deployment Perimeter, deployment Internal, performance_impact Low, confidence Medium, signature_severity Informational, tag kcptun, tag tunneling, updated_at 2026_10_08, mitre_tactic_id TA0011, mitre_tactic_name Command_And_Control, mitre_technique_id T1572, mitre_technique_name Protocol_Tunneling;
)

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