alert http $EXTERNAL_NET $HTTP_PORTS -> $HOME_NET any (msg:"ET WEB_CLIENT Possible HTTP 404 XSS Attempt (External Source)"; flow:from_server,established; content:"HTTP/1.1 404 Not Found|0d 0a|"; depth:24; nocase; content:"<script"; nocase; within:512; classtype:web-application-attack; sid:2010518; rev:4; metadata:affected_product Web_Browsers, affected_product Web_Browser_Plugins, attack_target Client_Endpoint, created_at 2010_07_30, deployment Perimeter, confidence Medium, signature_severity Major, tag Web_Client_Attacks, updated_at 2019_07_26;)