Half of businesses are restricting employees' access to social-networking site Facebook, due to concerns about productivity and security.
According to research by security company Sophos, 43 percent of workers polled said their employer blocks Facebook access completely.
A further 7 percent said access is restricted depending on whether it's required for a particular job.
"I think it's a growing concern for employers for a number of reasons," said Graham Cluley, senior technology consultant at Sophos. "The most pressing concern at the moment is one of productivity...Some people are spending an inordinate amount of time on nonwork-related Web sites."