ET WEB_CLIENT PDF Name Representation Obfuscation of Action

Query · suricata

flow:established,to_client;
content:"|0d 0a 0d 0a|PDF-";
content:"/"; distance:0;
content:!"Action"; within:6;
content:"#"; within:16;
pcre:"/\x2F(?!Action)(A|#41)(c|#63)(t|#74)(i|#69)(o|#6F)(n|#6E)/";
Raw source ET WEB_CLIENT PDF Name Representation Obfuscation of Action · Suricata
Esc
Published by Emerging Threats Open ↗, licensed under BSD 3-Clause ↗. Line breaks added for readability; the rule is otherwise unchanged. 
alert http $EXTERNAL_NET any -> $HOME_NET any (
    msg:"ET WEB_CLIENT PDF Name Representation Obfuscation of Action";
    flow:established,to_client;
    content:"|0d 0a 0d 0a|PDF-";
    content:"/"; distance:0;
    content:!"Action"; within:6;
    content:"#"; within:16;
    pcre:"/\x2F(?!Action)(A|#41)(c|#63)(t|#74)(i|#69)(o|#6F)(n|#6E)/";
    reference:url,blog.didierstevens.com/2008/04/29/pdf-let-me-count-the-ways/;
    classtype:bad-unknown;
    sid:2011529; rev:6;
    metadata:affected_product Web_Browsers, affected_product Web_Browser_Plugins, attack_target Client_Endpoint, created_at 2010_09_27, deployment Perimeter, signature_severity Major, tag Web_Client_Attacks, updated_at 2019_07_26;
)

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