Employers are increasingly putting the brakes on employee use of social networking sites on the job, according to a new survey. The research, released Wednesday by ScanSafe, a provider of SaaS Web security, said its data shows more employers are blocking sites such as Facebook and Twitter. The results run counter to a story published by CSO in March 2009 that cites research which found most employers do allow access to Web 2.0 in the office (See: Facebook, Twitter, LinkedIn: Employers Warm to Web 2.0 Access).The results come from an analysis of more than a billion Web requests processed by the company, officials said. ScanSafe saw a 20 percent increase in the number of customers blocking social networking sites in the last six months. According to their data, 76 percent of companies are choosing to block social networking and it is now a more popular category to block than online shopping (52 percent), weapons (75 percent), alcohol (64 percent), sports (51percent) and Webmail (58 percent)."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," said Spencer Parker, director of product management at ScanSafe, in a statement on the findings. "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, online banking and Webmail."The research did not include explanations from customers for the increase in social network restrictions, but ScanSafe officials speculated it may be due not only to security concerns, but also to decreased productivity when the use of Web 2.0 sites is allowed among employees."In economic times like these, having a productive workforce is more important than ever and companies are now often expecting employees to work harder for less," ScanSafe officials said. "Restricting access to non-work related sites could be a way to encourage this much needed productivity."