Rideshare phenomenon Uber is hiring Facebook's security chief Joe Sullivan, a former Department of Justice cybercrime prosecutor, as its new chief security officer.

Uber CEO Travis Kalanick says the hiring move illustrates his company's commitment to ensuring safe and secure systems and its seriousness regarding shoring up Uber's cybersecurity efforts.

"We are both in cyberspace and on city streets all at once; a bridge between bits and atoms. And as we get into tens of millions of rides a week, we continue to challenge ourselves to do even better when it comes to safety and data security," Kalanick writes at the Uber blog in announcing Sullivan's hire.

The hiring comes just two months since Uber acknowledged it suffered a database intrusion in 2014 and admitted waiting several months to alert its drivers about the breach, which put drivers' names and license numbers at risk.

A report earlier this week claims the company may have charged users for rides which were not actually taken and Uber says it is investigating the potential fraud and issuing refunds. One report says Uber's user account information may be being sold online.

The move also comes when companies are being pressured to ensure critical data and networks are protected to ensure user privacy. Uber, which is handling millions of fares daily in 300 cities across 56 countries, says its business has become "a critical part of the infrastructure of cities," and "a bridge between bits and atoms."

"As we get into tens of millions of rides a week, we continue to challenge ourselves to do even better when it comes to safety and data security," writes Kalanick.

Sullivan, who takes on his new role in late April, has spent the last five years as a chief security leader at social network Facebook and prior to that served in similar roles at eBay and PayPal. He spent eight years at the DOJ.

Sullivan, writing in the same blog post, says he's excited about the job and Uber's mission in revolutionizing transportation.

"I had the good fortune to work at two amazing companies - eBay and Facebook - when they were growing rapidly. I look forward to bringing the best practices that I've learned along the way to Uber and doing defining work in bridging the divide between the digital and physical worlds. There's a great foundation of safety already in place; my goal is to make it even stronger," writes Sullivan, noting the decision to leave Facebook was not easy.