German financial weekly Wirtschaftswoche reported this weekend that more and more German companies are banning popular internet services, including Facebook and Twitter.
A spokesman for the high-street bank Commerzbank told the magazine, "For the majority of our employees, many external social media offers are inaccessible for security reasons."
"E-mail used to be the tool used most often to introduce damaging software. Today it is social networks," commented Christian Fuchs of the IT security company Kaspersky.
Other companies that have banned the use of Facebook in the office include auto-giant Volkswagen and the building material company HeidelbergCement.
But companies clearly have other motivations for banning the use of online social networks. Facebook has around 500 million members worldwide, including over 10 million in Germany, and a recent study in the US found that no other site is visited more often from US offices.
Auto company Daimler admitted to the magazine that, "For productivity reasons, access to social networks may be blocked in certain offices."
The security company Clearswift recently conducted a study which found that 56 percent of Germans read private emails every day at work, while 40 percent use online banking. More than a third use social networks, while almost a quarter watch videos online.
Accordingly, the study found that 30 percent of German companies fear that allowing employees unrestricted access to social networking sites could negatively affect productivity. But 56 percent of those companies say the main reason for blocking certain sites remains security concerns.