How to stop ad-on / parked domains from getting picked up by search engines

[yru]

I have about 15 domain names parked on a website of mine and they are beginning to get picked up by the search engines. I believe a few of the dn’s had some previous links. I am worried about getting penalties for having cloaked pages etc. What can I do? Thanks.

ADMIN: I just realized I posted the same thing in this thread about a month ago. Please delete if you get a chance.