Excluding RSS Feed from search engines?

Hi Everyone, I'm using VBulletin 3.8.4 and vBSEO 3.6.0 RC2. I recently added a new RSS feed to my forum, and I purge the old articles after a certain number of days. How can I exclude this particular group from being seen by the search engines? I used to remember how to do this, simply forgot..

The easiest way is to make this forum for members only. Guests/bots will never see it.

The feeds are EBay RSS Feeds. I depend on visitor traffic seeing them and clicking on the links. How else can I do this?

My main concern is the relative short shelf life of these posts. I delete them every few days so they never build up and have any real content. I delete these every few days because they fill up the forum they are in quite fast. They are just auction item listings, and while the keyword strength has got to be through the roof, they aren't meant to be long-term content that google is interested in indexing. Just hoping to eliminate them indexing these RSS groups I have to avoid any penalty for what might look like an attempt at "gaming" the system.

If you want bot traffic to them, then there's really no good option. your webmaster tools will fill up with a bunch of 404s for all the deleted threads.