$16 MILLION on Mark Zuckerberg's security in just 5 years due to 'specific threats'

Facebook has spent more than $16 million protecting Mark Zuckerberg and his family in just five years after 'specific threats' to the 31-year-old.

The firm disclosed the staggering amount spent on security for Zuckerberg - the fourth richest person in the world - in a regulatory filing on Wednesday.

It reveals that, in 2015, $5 million was invested in bodyguards and other protective services to ensure

the safety of its founder and CEO.

The substantial sum is in fact a mark down from the $6.2 million spent on his security in 2014.

'Because of the high visibility of our company, our compensation & governance committee has authorized an "overall security program" for Mr. Zuckerberg to address safety concerns due to specific threats to his safety arising directly as a result of his position as our founder, Chairman, and CEO,' it reads.

'We require these security measures for the company's benefit because of the importance of Mr. Zuckerberg to Facebook, and we believe that the costs of this overall security program are appropriate and necessary.'

The 31-year-old was the subject of an ISIS threat video earlier this year, which featured his face littered with bullet holes. Jack Dorsey, Twitter's CEO, also appeared in the video. 

It is not clear whether this video is one of the threats that has driven Facebook to pour millions into Zuckerberg's security detail.  

In the 25-minute video, the militants claim they control more than 10,000 Facebook accounts and 150 Facebook groups - and warn they will retaliate to any attempt to drive them off the sites. 

The threat came after both Zuckerberg announced an intense push against terrorist users on their social networks.

Facebook has vowed to follow Twitter's example in shutting down accounts that have terrorist links. 

Sheryl Sandberg also called on users to 'attack' any terrorist-linked posts with 'likes'.