ET HUNTING Connectivity Check With Go User-Agent

Query · suricata

flow:established,to_server;
urilen:9;
http.method;
content:"GET";
http.uri;
content:"/ncsi.txt"; fast_pattern;
http.host;
content:"www.msftncsi.com"; bsize:16;
http.user_agent;
content:"Go-http-client/"; startswith;
http.header_names;
content:!"Referer|0d 0a|";
target:src_ip;
Raw source ET HUNTING Connectivity Check With Go User-Agent · 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 HUNTING Connectivity Check With Go User-Agent";
    flow:established,to_server;
    urilen:9;
    http.method;
    content:"GET";
    http.uri;
    content:"/ncsi.txt"; fast_pattern;
    http.host;
    content:"www.msftncsi.com"; bsize:16;
    http.user_agent;
    content:"Go-http-client/"; startswith;
    http.header_names;
    content:!"Referer|0d 0a|";
    classtype:bad-unknown;
    sid:2044794; rev:1;
    metadata:attack_target Client_Endpoint, created_at 2023_03_28, deployment Perimeter, confidence Medium, signature_severity Informational, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2023_03_28;
    target:src_ip;
)

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