After his trip was over, he discovered someone had hijacked his e-mail account and sent a message to hundreds of his contacts, asking for money.
Most of Carter's contacts recognized the scam from the poor grammar. Unfortunately, one older friend fell for it, sending $2,000 to the scammers.
Travelers are especially vulnerable to hackers because they often use computers and wireless networks in hotel lobbies, cafes and airports.
"If you are using an open Wi-Fi network, you are extremely vulnerable," says computer security consultant Kevin Mitnick, who served five years in prison for computer capers.
Here are some steps you can take to protect yourself.
Set up a spare e-mail address
Create a dedicated e-mail account for use on the road, with a password that is different from what you use for bank and credit card information. Let your contacts know you'll be using that account on vacation.
Be aware that hackers can monitor communication sent on wireless networks - and even wired hotel networks. That's not to say every hot spot is dangerous. But when using your laptop in a public place, you obviously want up-to-date security programs.
Change your settings
Disable file-sharing on your laptop. It's also a good idea to turn off Bluetooth, printer-sharing and disable ad hoc network connections.
Many experts say you should not send any sensitive data while in a hot spot. If you want to be careful, that means avoiding banking, shopping and checking credit card accounts.
Cover your tracks
If using a shared computer, clear your browsing history to remove traces of your passwords and the Web sites you've visited before you log off. But this won't ward off keyloggers or other malware software that grabs passwords. That's why Mitnick says he'd only use a shared computer to check e-mail as a last resort - and then would immediately change all his passwords as soon as he got to a secure computer.