@Vincenzo -- also keep in mind that, in cases of fraud, your maximum liability is $50. That's right -- the credit card company will have to either eat the rest or get it from someone else. That is a federal law designed to protect consumers from fraud.
A lot of credit card companies will even waive that $50 fee and that is doubly true if you let them know about the fraudulent charge right after it has taken place. The lesson here is that it is a very good idea to check your credit card activity regularly. The world is full of thieves and fraudsters wanting to get their mitts on your credit card number, so make sure to keep an eye on your account.