What can I do about this unbearable coworker?

I was at work on my laptop, when a coworker comes up to me and asks me what I am doing. Before I could answer him, he takes a look at my laptop. I was checking my bank statement. He see's the money I have in my account and immediately starts asking me for a loan. I said no, and he replies ah come on, it's not like you do not have it. I said no again and got up and left. Now he is badmouthing me to other employees. What can I do?