“ There is nothing a user could have noticed,” Williams said, noting that the optimisation software had a proper digital certificate, which means that other computers automatically trust the program. Talos researcher Craig Williams said it was a sophisticated attack because it penetrated an established and trusted supplier in a manner similar to June’s “NotPetya” attack on companies that downloaded infected Ukrainian accounting software. At the time of the acquisition, the company said 130 million people used CCleaner.Ī version of CCleaner downloaded in August included remote administration tools that tried to connect to several unregistered web pages, presumably to download additional unauthorised programs, security researchers at Cisco’s Talos unit said.

CCleaner is the main product made by London’s Piriform, which was bought in July by Prague-based Avast, one of the world’s largest computer security vendors. It cleans up junk programs and advertising cookies to speed up devices. The malicious program was slipped into legitimate software called CCleaner, which is downloaded for personal computers and Android phones as often as five million times a week. San Francisco - Hackers broke into British company Piriform’s free software for optimising computer performance last month potentially allowing them to control the devices of more than two million users, the company and independent researchers said on Monday.

Ccleaner piriform talos