Users of Avast-owned security application CCleaner version 5.33 for Windows have been advised to update their software immediately, after researchers discovered criminal hackers had installed a backdoor in the tool. The tainted application allows for download of further malware, be it ransomware or keyloggers, with fears millions are affected. According to Avast's own figures, 2.27 million ran the affected software, though the company said users should not panic.
The malware would send encrypted information about the infected computer - the name of the computer, installed software and running processes - back to the hackers' server. The hackers also used what's known as a domain generation algorithm (DGA); whenever the crooks' server went down, the DGA could create new domains to receive and send stolen data. Use of DGAs shows some sophistication on the part of the attackers.
Moving Forward: Users can download CCleaner 5.34 from Avast’s website if they haven’t already done so. Previous releases are also still available on the company’s website, but the infected version has been removed from the company’s servers. You’ll also want to perform an anti-virus scan on your computer.