But those aren't the zombies in question. Zombie debts are those old, unpaid debts owed companies that have given up trying to collect. Now, however, they are selling those debts to debt collectors, who miraculously bring them back to life and resume the pursuit. Of you.
Dayana Yochim, writing for The Motley Fool, has some savvy tips about dealing with phone calls from the dead (debt), the foremost being, admit nothing. Say nothing that might indicate your recognition of the debt, because, like brains, your reaction feeds the zombie debt. Ask for details, check it against your own records.
That doesn't mean you can ignore a valid debt, though. It can wreak havoc on your credit rating. So if you do in fact owe the debt, and substantiate that the debt collector is in fact the owner of that debt, you'd be well advised to make arrangements to clean up that particular dirty, lurching problem.
Because sunlight and baseball bats don't work against this kind of zombie.