The report, from employee training firm WeComply, found that 39 percent of U.S. workers incorrectly believe a message sent from their personal e-mail account on a work computer remains a personal record. And two-thirds of all workers did not understand that personal instant messages to friends could become business records.

The findings take on particular significance given new rules for disclosing electronically stored information during lawsuits. The report said those changes to the Federal Rules of Civil Procedure, which took effect December 1, make it more likely that inappropriate e-mails, Web searches, IMs and other electronically stored data will surface in pretrial discovery.

WeComply president David Simon says the stakes are high for employees to know how to keep their electronic noses clean at work.

“Anything you do today on your computer may see the light of day,” he says. “If you’re not careful, it could expose you or your company to legal liability.”

Many companies today are peeking in on their employees at the computer. A study last year on electronic monitoring and surveillance by the American Management Association and the ePolicy Institute found that about 75 percent of U.S. companies monitor workers' Web site connections. Fifty-five percent of companies retain and review e-mail messages, and 36 percent track content, keystrokes and time spent at the keyboard.

About a quarter of employers have fired workers for misusing the Internet, according to the AMA report.

A desire to cut down on workplace slacking and comply with government rules may be prompting companies to monitor computer use. But employers who do so should be careful, says Brian Hengesbaugh, an attorney with law firm Baker & McKenzie.

Depending on the promises the company has made, employees may reasonably expect to have a degree of privacy at work, he says. As a result, Hengesbaugh says, employers that plan to monitor electronic activities should notify workers that their computer use on the job is not private.

In addition, he says global companies that have a policy respecting privacy rights in Europe could inadvertently post that statement to a company Web site. American employees might then expect similar rights.

“They may reasonably interpret that those rules apply to them,” he says.

The WeComply report involved a survey of 1,000 U.S. workers. Younger workers tend to be less aware of computer-use realities than older ones are, according to the report. More than half of those under 55 did not understand that sending an e-mail to a friend created a business record, compared with 39 percent of those over 55, the report says.

—Ed Frauenheim