MyBB Community Forums

I thought there was a kind of plugin that do exactly what I want, I searched in the plugins but I did not found.

So I hope somebody can help me with this a plugin that protect members from viewing and posting into a forum. Only people who have entered a code/password can enter this specified forum.

This is a default feature, just enter a password into the password setting in the settings of the forum you want to password protect...

Is this also possible with a thread?

Not specific threads, only forums.

You can't password protect specific threads, no.