Hi, I cannot find an option to force gobuster in directory mode to filter negative/positive responses by the content instead of just status codes.

Let's say the site responds for non existing endpoint with example response

HTTP/1.1 200 OK
Date: Mon, 15 Mar 2021 10:28:13 GMT
Server: Apache/2.4.46 (Win64) OpenSSL/1.1.1h PHP/8.0.1
Content-Length: 1234
Content-Type: text/html; charset=UTF-8

Not found

In such case I would like to tell gobuster to treat Not found string as a negative server response. I think that filtering by content length would be a useful feature too.

This looks like quite popular issue and I believe that I might be just missing some flags :)