Employers are gradually tightening the reins on the Web sites workers can view. Among the most popular sites to block: social networking sites like Facebook, Twitter and Linkedin.

Results from a new survey by ScanSafe, a  SaaS Web security provider, found a 20% increase in the number of its customers blocking social networking sites in the last six months.

Currently, 76% of companies are choosing to block social networking and it is now a more popular category to block than online shopping (52%), weapons (75%), alcohol (64%), sports (51%) and Web mail (58%).

Employers don’t take the same stern approach to online banking and less than half (47%) of ScanSafe customers block this category.

“When Web filtering first became an option for companies we generally saw them block access to typical categories such as pornography, illegal activities and hate and discrimination,” comments Spencer Parker, director of product management at ScanSafe.

“In recent months, employers are obviously wising up to the dangers and negative impact on productivity linked to certain sites and more and more of our customers have chosen to block social networking.”

ScanSafe specifically found an increase in the number of customers choosing to block these categories in the last 6 months:

• 28% increase in travel
• 27% increase in restaurants and bars
• 26% increase in sports
• 26% increase in online shopping
• 19% increase in Job Searches
• 16% increase in Webmail

The analysts at ScanSafe surmise that, in tough economic times, having a productive workforce is more important than ever, and companies are now often expecting employees to work harder for less.

Many see restricting access to non-work related sites as a way to encourage much-needed productivity.

“Social networking sites can expose businesses to malware and if not used for business purposes can be a drain on productivity and bandwidth,” says Parker. “Given the option, companies are increasingly taking a sterner approach to the sites that their employees are allowed to access. I imagine before long, social networking will be up there with pornography in terms of categories blocked.”

Tags: block, Facebook, ScanSafe, social networking sites, survey