Researchers at a French institute have resurrected an extinct virus from the human genome. Yes, you read it right, they resurrected it from the human genome itself. The virus, dubbed phoenix, is from a class of viruses known as retroviruses which integrate their genome into the host. At a later time, they may get berserk and infect the host. But if they remain intergrated long enough, they get inactivated due to acquired mutations.
Check out this cool research here.
I think it is perfectly normal to resurrect a virus. How else would one learn things, unless he tries to do it.
But this type of research should be carried out under extreme security.