Malformed URLs

Among those who do web site security audits, one of the “tricks of the trade” used to learn more about a web site is to alter known valid URLs in certain ways, to try to come up with additional valid, but not advertised, URLs which can be used to reveal data and program source code. For example, if you know that the web site contains a valid URL, “http://www.mysite.com/shop/ordlist.asp”, you might also check to see if “http://www.mysite.com/backup/shop/ordlist.asp”, “http://www.mysite.com/shop/backup/ordlist.asp” or “http://www.mysite.com/shop/ordlist.asp.old”, in hopes that one of those other URLs will enable them to gain more access to a version of the ordlist.asp file.

Real World Back Doors

Does your web site have any old files on it, in “backup”, or “old” directories, or perhaps prior versions of files whose names end in “.old” or “.backup”? Do the permissions on those files or directories allow anyone but authorized administrators to access them? If so, remove the backup copies or ensure that you have set permissions on them so that arbitrary web users cannot access them.