404 detection looks at a user who is hitting a large number of non-existent pages and getting a large number of 404 errors. 404 detection assumes that a user who hits a lot of 404 errors in a short period of time is scanning for something (presumably a vulnerability) and locks them out accordingly. This also gives the added benefit of helping you find hidden problems causing 404 errors on unseen parts of your site. All errors will be logged in the "View Logs" page. You can set thresholds for this feature below.