In recent months, I've met at least three people who have been the victim of hackers who've taken over their Gmail accounts and sent out e-mails to everyone in the address book.

The e-mails, which appear legitimate, claim that the person has been robbed while traveling and begs that money be wired so that the person can get home. What makes the scam even more effective is that it tends to happen to people who are actually traveling abroad—making it more likely that friends and families will be duped.

Although it's widely believed that a strong password is one of the best defenses against online fraud, hackers increasingly employ highly effective ways for compromising accounts that do not require guessing passwords.

This means that it is more important than ever to practice "defensive computing"—and to have a plan in place for what to do if your account is compromised.