I have noticed, in recent weeks, that when I check the Who's online, there are dozens of "customers" with a cart, and they all have different numbers of "Gift certificates" but they don't have names (just IP), and they never check out. Right now, I see 87 of them, and they all have the same IP (and there is nobody else in the store).

What is that? Can I get rid of them? If so, how?