Imagine logging on to Facebook only to find it had been shut down for offering child pornography? Visitors to some 8,000 websites in Denmark faced just that, when a “human error” by Danish police labeled most of the internet a sexual predator.

­With the Internet under attack by a string of abbreviations ranging from ACTA to SOPA, avid web surfers have been a bit jumpy as of late.

In these troubled times, imagine the shock many Danish users of the Siminn internet service provider (ISP) received when a casual workday visit to Google or Facebook left this message ominously glowing on the screen:

“The National High Tech Crime Center of the Danish National Police [NITEC], who assist in investigations into crime on the Internet, has informed Siminn Denmark A/S, that the Internet page which your browser has tried to contact may contain material which could be regarded as child pornography.”

For several hours Thursday, that message appeared on the screens of 8,000 different websites, virtually bringing down large swaths of the Internet across the country.

How did it all happen?

According to NITEC chief Johnny Lundberg, it didn’t take much.

The whole fiasco apparently began when an employee at the police center switched seats with his colleague.