What is the best defense against a computer virus (in SE IV

)?
Will a self-destruct mechanism protect me? What if I put an auxiliary bridge on my ship? Will the enemy then have to overcome my computer AND use marines to take over the ship?
I read somewhere that a computer virus does not take over a ship -- it just reduces it's movement t 1. Is that correct?? If so, then are viruses useless against starbases?
Thanks!
Merry