Xobor.com - official support forum

Yes it is.

Go to admin → forum → choose forum that should be locked out and click on it.

it's neccesary that you:

- let the forum always show up, even if somebody can't read in it (if they din't see the forum, they can't click it to enter the password)
- create a password
- take away the rights to read in the forum (but still leave the other rights you want them to have)