Think you can get away with using e-mail and the Internet in violation of company policy? Think again.

A new survey found that more than a quarter of employers have fired workers for misusing e-mail and one third have fired workers for misusing the Internet on the job. The study, conducted by the American Management Association (AMA) and The ePolicy Institute, surveyed 304 US companies of all sizes.

The vast majority of bosses who fired workers for Internet misuse, 84 percent, said the employee was accessing porn or other inappropriate content. While looking at inappropriate content is an obvious no-no on company time, simply surfing the Web led to a surprising number of firings. As many as 34 percent of managers in the study said they let go of workers for excessive personal use of the Internet, according to the survey.

Among managers who fired workers for e-mail misuse, 64 percent did so because the employee violated company policy and 62 percent said the workers' e-mail contained inappropriate or offensive language. More than a quarter of bosses said they fired workers for excessive personal use of e-mail and 22 percent said their workers were fired for breaching confidentiality rules in e-mail.

Companies are worried about the inappropriate use of the Internet, and so 66 percent of those in the study said they monitor Internet connections. As many as 65 percent of them use software to block inappropriate Web sites. Eighteen percent of the companies block URLs (uniform resource locators) to prevent workers from visiting external blogs.

Companies use different methods to monitor workers' computers, with 45 percent of those participating in the survey tracking content, keystrokes and time spent at the keyboard. An additional 43 percent store and review computer files. Twelve percent monitor blogs to track content about the company and 10 percent monitor social-networking sites.

Companies are keen to track employee e-mail and Internet behavior in part due to legal fears. According to research done by the AMA and ePolicy in 2006, 24 percent of companies in the study had e-mail subpoenaed by courts and another 15 percent have faced lawsuits based on employee e-mails.

The researchers found that even though only two states require companies to notify their workers that they're monitoring them, most tell employees of their monitoring activities. Of the companies that monitor workers in the survey, 83 percent said they tell employees that they are monitoring content, keystrokes and time spent at the keyboard. As many as 84 percent tell employees that they review computer activity and 71 percent alert workers that they monitor their e-mails.