The backlash against Facebook is on. A survey has found that 43 percent of employees are now being blocked from Facebook access during office hours.

Sophos carried out a global poll of 600 workers. The security firm found that 43 percent of employees were unable to access Facebook at work. A further 7 percent could get only restricted Facebook access. No deskbound poking for them.

Big City firms LloydsTSB, Credit Suisse and Goldman Sachs are all thought to have blocked access to Facebook.

20% of Facebook users are IDiots

But the workers do have some power, comrade. A feisty 8 percent of respondents said that Facebook access was allowed at their workplace because bossess feared a backlash if it was stopped. This means that either (a) we live in enlightened times, (b) Mr Barraclough from Porridge is a company director or (c) 8 percent of respondents were journalists.

Incredibly, bosses fear that employees will waste time on Facebook. Personally, I can't think what they would mean. The seven hours I spend on Facebook each day is time well spent. (When I do write the review, it will be thorough.)

But there's more to fear for the gaffers than the proletariat being idle. In a separate poll carried out by Sophos, two thirds of bosses said that they were concerned about co-workers sharing too much information on Facebook. (They claim that they wish to avoid potential phishing attacks, but I suspect that no boss wants his PA spreading rumours about personal hygiene issues.)

"More businesses are restricting access to these kinds of sites. Employees may not like it, but these websites can represent a security risk if used carelessly. Unless there's a work purpose, many firms do not see any reason why staff should need to access them during work time," said Graham Cluley of Sophos.

Sophos has published a security and marketing guide to Facebook on its website. Don't let your boss know.