One third of companies employ staff specifically to monitor or analyze e-mail content, according to a survey of 220 organizations released on Monday.

The study, funded by data-loss prevention firm Proofpoint, found that 46 percent of companies regularly audit outbound e-mail to prevent confidential information from leaking out of the organization. Almost four out of five companies have staff who regularly analyze or monitor e-mail, and a third employ workers to specifically focus on that task -- double the proportion of workers focused on the issue in 2008.

Proofpoint argues that the trend has accelerated because of the use of social media and the current difficult economic times. More than a third of the surveyed companies acknowledged a leak of sensitive or embarrassing information in the past year, half again as many as in 2008.

E-mail accounted for the largest number of data-leak investigations, with 43 percent of all companies investigating e-mail leaks. Another 18 percent of companies investigated employees because of a blog post, and the same number investigated workers for posting video to YouTube and other sites.

In total, more than half of companies reprimanded an employee for their use of media, and nearly a third of firms have fired a worker for violating information sharing policies, the survey found.