If you install CCleaner 5.33, your machine hooks into a bot network. The details are complex, but the upshot is clear: Somebody managed to tack a malware package onto the legitimate distribution file for CCleaner.

If you installed CCleaner 5.33, you're infected During the installation of CCleaner 5.33, the 32-bit CCleaner binary that was included also contained a malicious payload that featured a Domain Generation Algorithm (DGA) as well as hardcoded Command and Control (C2) functionality. …Įven though the downloaded installation executable was signed using a valid digital signature issued to Piriform, CCleaner was not the only application that came with the download. 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. Talos recently observed a case where the download servers used by software vendor to distribute a legitimate software package were leveraged to deliver malware to unsuspecting victims. (Piriform was bought by antivirus giant Avast in July.)Įdmund Brumaghin, Ross Gibb, Warren Mercer, Matthew Molyett, and Craig Williams at Talos report: I just checked, and the current version available from Piriform is version 5.34. 11.Īfter notifying Piriform, CCleaner was, ahem, cleaned up and version 5.34 appeared on Sept. 15 and which, according to Talos, was still the primary download on the official CCleaner page on Sept.

Talos Intelligence, a division of Cisco, just published a damning account of malware that it found hiding in the installer for CCleaner 5.33, the version that was released on Aug. 15, a couple of nasty programs came along for the ride.

If you installed the free version of CCleaner after Aug.

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