Facebook has taken on Yahoo’s CISO as its CSO.

In a friendly nod to his new masters, Alex Stamos used his Facebook page to announce that he would be starting the job on 29 June, also updating his employment status on the site.

During his tenure at Yahoo, the Berkeley graduate has championed the cause of user privacy, pushing Yahoo to adopt an encrypted email service. His stated reasons for his move to Facebook suggest that he is keen to undertake similar activism there:

"The Internet has been an incredible force for connecting the world and giving individuals access to personal, educational and economic opportunities that are unprecedented in human history. These benefits are not without risk, and it is the responsibility of our industry to build the safest, most trustworthy products possible.

"This is why I am joining Facebook. 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.

"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."

Facebook and its founder and CEO Mark Zuckerburg have a mixed history on the privacy issue. Zuckerburg famously declared in 2010 that the age of privacy was dead and internet users were no longer concerned about sharing information. In 2012 Facebook‘s U-turn began with the establishment of a ‘privacy product and engineering team’ and more recently Zuckerburg has been vocal on the issue.

An open letter to Zuckerburg from privacy activists singled out privacy as one of the key concerns with the ‘internet.org’ project. Stamos’s mention of "the remaining 2/3rds of humanity we have yet to connect" suggests that he plans to address these concerns.

Stamos has also challenged the NSA over security ‘backdoors’ in the wake of the Edward Snowden case.