Devious New Phishing Attack Outsmarts Typical Defenses

Andrew Brandt

Andrew Brandt is a senior associate editor for PC World. You can send him e-mail at consumerwatch@pcworld.com.

Illustration by Mark Matcho

You might think that you know how to protect yourself from phishing: Don't click the links in e-mail that purports to be from banks or other institutions. But that defense is no longer ironclad: Phishers have found a new way to snare data without your clicking a link.

Anyone with an inbox has seen a standard phishing attack: You get an e-mail warning you that something terrible has happened to your bank account and asking you to go to the bank's site to reenter your personal data. If you click the link in the e-mail, however, you go not to your bank but to a server run by a criminal who gathers all the data you enter. The best advice has been to ignore the link in the e-mail and instead type the URL of your bank's site into your browser. But that was then. Now--without protection--you can't even trust your browser when you type the address yourself.

Here's how the new phishing scam works. You receive an HTML e-mail message, and you open (or even just preview) the message in your e-mail client software. Windows PCs lacking one particular Microsoft security patch (available here) will run a tiny JavaScript applet as the client renders the HTML. The QHosts Trojan horse applet modifies the PC's Hosts file so that when you type in a bank's URL you actually go to a site controlled by the fraudsters. Since phishers have gotten very good at mimicking real sites, you may never know you're at the wrong one.

Spybot Search & Destroy lets you "lock" the Hosts file, preventing any other program from changing it. The Options tab in WinPatrol causes that program to pop up a dialog box if software attempts to change your Hosts file. And in the paid ZoneAlarm Pro firewall or ZoneAlarm Security Suite, you can enable an option in the Privacy Settings menu called Hosts File Protection that both locks the Hosts file and alerts you when something tries to change it.

While the impact of QHosts has been limited so far, phishers are likely to use this new technique much more in the near future. The fact that the Hosts file is easy to protect will be cold comfort to future victims who get hit with the next QHosts-like phishing scam.

--Andrew Brandt