Facebook was back up and running on Friday after being offline for about two and a half hours late Thursday and early Friday, the “worst outage we’ve had in over four years” a company programmer reported on his blog.

The company said the shutdown of the popular social networking site, where users can share their thoughts and pictures and play games with other member, was due to an error in an automated system.

It cut off service in the United States, Europe and South America. A spokesperson confirmed the site was again operational.

Robert Johnson, the programmer, apologised on his blog for the incident.

The automated system in question was tasked with verifying configuration values and replacing invalid data with updated information. A change in settings resulted in the system attempting hundreds of thousands of fixes, overwhelming Facebook’s system.

“The way to stop the feedback cycle was quite painful — we had to stop all traffic to this database cluster, which meant turning off the site,” wrote Johnson. “Once the databases had recovered and the root cause had been fixed, we slowly allowed more people back onto the site.” Johnson wrote that the problematic system had been turned off and a permanent fix was being sought.

Keywords: Facebook