Some speculate that SETI may be in danger of downloading an extraterrestrial virus or trojan.
Is SETI at risk of downloading a malicious virus from outer space?
I think it is a possibility but I think we would need to develop the proper technological advancements before this could be a real threat. For example, when we creat an advanced A.I. it is possible that the E.T. A.I.'s may assimilate it.
I can't help but think of this movie: