Cyber security rock star Alex Stamos announced in a Facebook post that he’s leaving Yahoo (YHOO) to become the chief security officer at Facebook (FB), Washington Post reports.  In poaching Stamos, Facebook fills the void left by former chief security officer Joe Sullivan, who left Facebook to join the Uber team in April.

“There is no company in the world that is better positioned to tackle the challenges faced not only by today’s Internet users but for the remaining 2/3rds of humanity we have yet to connect,” said Stamos in his post. “The Facebook security team has demonstrated a history of innovation as well as a unique willingness to share those innovations with the world, and we will build upon that history in the years to come.”

Stamos is probably best known for his outspoken stance against government intrusion into user information. Following the Edward Snowden leaks, Stamos made headlines by going head to head with NSA Director Adm. Mike Rogers at a New America Foundation cybersecurity conference, arguing that tech companies should not be required to build backdoors granting government agencies access to private user data.

In line with this objective of universal user security, Stamos spearheaded a major security overhaul at Yahoo. He revealed plans to create a Yahoo Mail plugin that would provide end-to-end encryption for e-mails, meaning only senders and recipients could access them.

Facebook’s decision to bring on Stamos may indicate a desire to change the direction for the company, which has encountered criticism for selling web-browsing and other data to advertisers in blatant disregard for user privacy. It’s not unlikely that Stamos will initiate some changes to this policy in an effort to better protect user information.

And Facebook seems excited for the innovative solutions that Stamos will bring to his new company. Colin Stretch, Facebook’s vice president and general counsel, told the Washington Post that Stamos “is a leader with deep technical security knowledge and experience. We’re thrilled that he is joining Facebook as our new Chief Security Officer to help us create even greater impact.”