lucy24 - 12:26 am on Jul 29, 2013 (gmt 0)
As far as I know, Joomla is commonly hosted on Apache server and Apache uses .htaccess You can edit .htaccess to set up 404 or 410 response codes or to set up a 301 redirect to a correct URL.
It shouldn't be necessary to use htaccess-- or, for that matter, IIS equivalent-- to issue a 404. A 410, yes, because that's an intentional statement from the site. But a 404 is the default response when the server can't find a file.
One thing you can and should do is look at the "URL parameters" area of gwt. There should already be a list of all the parameters they've found. Each one should be classified as, first, "affects page content" or "doesn't affect page content", and then among those that do affect page content, there's an array of "ignore" flags. If you find any listed parameter that you don't use at all, you may need to flag it manually as "doesn't affect page content".
You should also make sure that if you yourself request a garbage URL-- either a nonexistent path, or something with bogus parameters-- you get a 404 "Can't find this page" response. If you don't, you will need to consult joomla experts, because this is a CMS issue.