In a LinkedIn account summary, Stamos describes himself as a "security executive who is passionate about building an Internet that is safe and trustworthy for everyday users."
Stamos will replace Joe Sullivan who left Facebook in April to join Uber Technologies Inc. Facebook and Yahoo could not be reached for comment outside regular business hours.

Facebook has also partnered security software firm Kasperky to help its users detect and clean malware from their computers. 'Malware' is an umbrella term used to refer to computer viruses, worms, trojan horses, ransomware, spyware, adware and other malicious programmes.

Facebook said for the past year, it has been working with anti-malware companies like ESET, F-Secure and Trend Micro to offer free malware clean-up software to its users.
"To make this programme even more effective, Kaspersky Lab is bringing their expertise to our malware clean-up efforts. If we detect malware on your computer, we will offer Kaspersky Malware Scan for Facebook among our other clean-up tools to help take care of the problem," Facebook said in a blogpost.
It added that in the past three months, Kaspersky Lab has helped protect more than 2.6 lakh people accessing Facebook from malware.
"Thanks to the collaboration with these companies (Kaspersky and others), in the past three months, we have helped clean up more than 2 million people's computers that we detected were infected with malware when they connected to Facebook," Facebook Software Engineer Threat Infrastructure Team Trevor Pottinger said in the post.
In these cases, Facebook presents a clean-up tool that runs in the background while the user continues using the website and they get a notification when the scan is done to show what was found, he added.
"Keeping links to malware off of our platform is a core function of our security team... We use a combination of signals to help find infections and get the malware off your computer for good, even if the malware isn't actively spreading spam or harmful links," he said.