Passwords are your first line of defense against intruders. But, as Holland points out, even the most careful people sometimes have password breaches. "I've helped chief privacy officers from health care and security firms," he notes. "If they're getting hit, then anyone is vulnerable." While Holland notes the importance of having a good password, he emphasizes that the most important thing is paying attention to password breach notifications. If you hear that one of your passwords may have been breached, he counsels, change it immediately. And, because many of your accounts may be linked, he notes, it's not a bad idea to change the rest of your passwords as well.