The very first defense is to tell people to look at the links. A memorandum showing people what the double URLs look like will diminish risk.

If they see anything that looks like another link inside a link, it may be hostile. Such a link is at least a deceptive link.

The links will look like:

http://Friendly_Name.org/stuff.../http://some_other_name
or
http://Friendly_Name.org/stuff.../http://some_other_name/stuff...

Or IP addresses may be used, as in:

http://Friendly_Name.org/stuff.../http://123.54.65.123
or
http://Friendly_Name.org/stuff.../http://123.54.65.123/stuff...