Forum PRIVATE to members only??

Go to Forum Admin > Settings > Privacy.

Set your forum to private.

We recommend that forums stay public for a few reasons:

1. It allows the search engines to find your forum and send new visitors to your forum. 1/3 of all traffic to lefora forums comes from a google search.

2. Only public forums are listed in our directory, private forums are not.

3. We have really strong spam detection, so we'll ensure public forums do not get taken over by spammers.

As for attachments, only 'members' of the Lefora userbase can download attachments (images anybody can see, but only lefora registered users can download files).  So if your concern is that attachments cannot be download by guests, this might meet that requirement.

You could also use password-protected archives (eg .rar) and pm the password to trusted members...