The SANS Institute has some controversial advice for computer security professionals looking to lock down their networks: spear-phish your employees.

That's what the U.S. Military Academy at West Point did in 2004 to a group of 512 cadets, selected at random for a test called the Carronade. The cadets were sent a bogus email that looked like it came from a fictional colonel named Robert Melvillle, who claimed to be with the academy's Office of the Commandant (The real Robert Melville helped invent a short range naval cannon called the Carronade nearly 250 years ago).

"There was a problem with your last grade report," Melville wrote, before telling the cadets to click on a Web page and "follow the instructions to make sure your information is correct."

More than 80 percent of the cadets clicked on the link, according to a report on the experiment.

Worse still, even after hours of computer security instruction, 90 percent of freshmen cadets still clicked on the link.

Spear-phishing attacks contain this kind of targeted information in order to seem more credible, but their goal is the same as a regular phish: trick the user into doing something he shouldn't, like giving up sensitive information.

Because these attacks rely on cooperation from their victims, it's hard to prevent them, said Alan Paller, director of research with SANS. "The only defense against spear phishing is to run experiments on your employees and embarrass them," he said.

Paller's organization compiles an annual report on the top to Internet security targets. This year "human vulnerabilities" will make their first appearance on a list that is typically made up of software products like Internet Explorer, databases, and file sharing applications.

That's because the human factor is being exploited in a growing number of targeted attacks as more and more online criminals come online in Eastern Europe and Asia, Paller said.

Although Microsoft Corp.'s Windows operating system has long the prime target of online attackers, the software giant has tightened up its security practices over the past few years.

But that hasn't deterred attackers, Paller said. In fact 2006 witnessed a surge in attacks that take advantage of unpatched vulnerabilities in new types of programs, like office applications, media players, backup software, and VOIP (Voice Over Internet Protocol) servers, Paller said.

The IDG News Service is a Network World affiliate.