Registration Advice

[Haro-san]

New to vBulletin and can't find enough info to fully understand registration... validation... moderated users... etc. Here's my delima...

• Created cat for group of private forums w/ sensitive data
• It requires pw to access which is inherited by forums in that cat.

Want: Once a user accesses I'd like to add them to user group for that cat. so they wouldn't have to go thru pword process on subsequent visits.
Question: How do I do that?

Problem: I don't like this level of security, seems to me it could be easily breeched. But the advantage is its super simple.
Problem: Also, if pword sec broken & need change pword, would the user have to go through the whole process again.
Question: Is there a more secure way that is still simple?

Would be nice: To completely hide this cat. from all users but those in the group
Problem: How would they join the group, be accepted as members and access the HIDDEN site.

For the "would be nice": It seems much more secure... the functionality seems built in as it works like the "requires validation" sites. Much more complicated, but that's the price for security. I just can't find enough info to know how to implement.

Any advice? I have looked for information, but seem to be working around the periphery of the problem.

thanks...