Stamos was one of the primary organizers of TrustyCon, a gathering of prominent technology experts last month who had pulled out of the RSA Security Conference in San Francisco amid growing discord over some technology companies' cooperation with US intelligence-gathering efforts.

Yahoo officials and Stamos could not be reached for comment on his appointment, which was announced on Monday on the company's blog by Yahoo senior vice-president Jay Rossiter.

The blog said Stamos will lead a team of Yahoo "paranoids" charged with making products as secure as possible.

Stamos most recently served as chief technology officer of security firm Artemis. Prior to that, he was a co-founder of iSEC Partners, a security company that was acquired in October 2010 by NCC Group, the parent of Artemis.