Security: Restricting access to vBulletin Forum

[mknapik]

I've got a forum set up that is intended to be accessed only by users of a software program I develop.

How can I secure my forum site so that it can only be accessed via a link within my program, and not through search engines, or a bookmark made from a previous visit?

[ZomgStuff]

An .htaccess file I suppose.

[Antivirus]

Yep, .htaccess is the best way to do it. Place it in your forum root directory and nothing will be able to access or index without an additional username / password