Captcha when posting a new reply

[flup]

Hi all,

it's been a while since I've been around here so first of all sorry if the answer to the following questions is very simple!

A client of me wants to have a discussion forum on his website, I recommended vBulletin because of the large amount of plugins that are available and the active userbase. All of his needs are inside the vBulletin package, except for one which I can't seem to find (neither as a plugin);

On his forum he want's registered members to have the ability to post new threads and guests should only be able to reply on existing threads. As far as I know, I can simply use the existing usergroup manager in the admincp to alter the abilities of these two usergroups and this should be fixed pretty quick.

However, this client also wants to make sure that no spam is being commented on the existing threads and thus he wants to have captcha (or a similar) security added to the quickreply and/or new reply page.

Is this an option within the default vBulletin package or would this require a mod (and would there perhaps be one around already?)

Thanks in advance!