Hackers have successfully breached CCleaner’s security to inject malware into the app and distribute it to millions of users. Security researchers at Cisco Talos discovered that download servers used by Avast (the company that owns CCleaner) were compromised to distribute malware inside CCleaner. “For a period of time, the legitimate signed version of CCleaner 5.33 being distributed by Avast also contained a multi-stage malware payload that rode on top of the installation of CCleaner,” says the Talos team.
CCleaner has been downloaded more than 2 billion times according to Avast, making it a popular target for hackers. Dubbed “crap cleaner,” it’s designed to wipe out cookies and offer some web privacy protections. 2.27 million users have been affected by the attack, and Avast Piriform believes it was able to prevent the breach harming customers. “Piriform believes that these users are safe now as its investigation indicates it was able to disarm the threat before it was able to do any harm,” says an Avast spokesperson.