Stop R-U-Dead-Yet? (R.U.D.Y.) attacks

R-U-Dead-Yet (R.U.D.Y.) attacks accomplish denial of service (DoS) by submitting long form fields. Use firewall rules to stop these attacks by blocking requests that do not have a legitimate session cookie.

This example combines three expressions to target HTTP POST requests that do not contain a legitimate authenticated session cookie.

The first expression uses the http.request.uri.path field to target the paths to secure from R.U.D.Y.:

http.request.uri.path matches "(comment|conversation|event|poll)/create"

The second uses a regular expression to match the format of a legitimate auth_session cookie. The not operator targets requests where that cookie is not formatted correctly:

not http.cookie matches "auth_session=[0-9a-zA-Z]{32}-[0-9]{10}-[0-9a-z]{6}"

The third expression targets HTTP POST requests:

http.request.method eq "POST"

The expressions are combined using the and operator. When an HTTP POST request to any of the specified URIs does not contain a properly formatted auth_session cookie, Cloudflare blocks the request: