Answer:
a. Zombie
Explanation:
Zombies- A cracker — a computer hacker who intends mischief or harm — secretly infiltrates an unsuspecting victim’s computer and uses it to conduct illegal activities. The user generally remains unaware that his computer has been taken over — he can still use it, though it might slow down considerably. As his computer begins to either send out massive amounts of spam or attack Web pages, he becomes the focal point for any investigations involving his computer’s suspicious activities. In one case of zombies it was found that over 1.5 million computers were affected in an attack.
