ET MALWARE Cobalt Strike Beacon Activity

Query · suricata

flow:established,to_server;
http.method;
content:"GET";
http.uri;
content:"/userid="; startswith; fast_pattern;
pcre:"/^[A-Z]{256}$/R";
http.header;
content:"Content-Transfer-Encoding|3a 20|base64|0d 0a|";
http.header_names;
content:!"Referer";
Raw source ET MALWARE Cobalt Strike Beacon Activity · 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 -> $EXTERNAL_NET any (
    msg:"ET MALWARE Cobalt Strike Beacon Activity";
    flow:established,to_server;
    http.method;
    content:"GET";
    http.uri;
    content:"/userid="; startswith; fast_pattern;
    pcre:"/^[A-Z]{256}$/R";
    http.header;
    content:"Content-Transfer-Encoding|3a 20|base64|0d 0a|";
    http.header_names;
    content:!"Referer";
    reference:md5,435f83b1ab70c68e34bd523bae4217e0;
    reference:url,twitter.com/bryceabdo/status/1372895643102969861;
    classtype:trojan-activity;
    sid:2032274; rev:1;
    metadata:attack_target Client_Endpoint, created_at 2021_03_22, deployment Perimeter, deployment SSLDecrypt, confidence Medium, signature_severity Major, tag c2, updated_at 2021_03_22, mitre_tactic_id TA0010, mitre_tactic_name Exfiltration, mitre_technique_id T1041, mitre_technique_name Exfiltration_Over_C2_Channel;
)

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