alert http $EXTERNAL_NET any -> $HOME_NET any (msg:"ET WEB_CLIENT PDF Name Representation Obfuscation of URL"; flow:established,to_client; content:"obj"; content:"<<"; within:4; content:"/"; within:50; content:!"URL"; within:3; content:"#"; within:7; pcre:"/\x3C\x3C[^>]*\x2F[^URL](U|#55)(R|#52)(L|#4C)/smi"; reference:url,blog.didierstevens.com/2008/04/29/pdf-let-me-count-the-ways/; classtype:bad-unknown; sid:2011533; rev:4; 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;)