CCleaner is marked as a potentially harmful application by Windows

Microsoft is now detecting the popular CCleaner Windows optimization and registry cleaner as a potentially harmful application (PUA) in Microsoft Defender.

CCleaner is a junk file removal program, registry cleaner and general Windows performance optimization utility developed by Piriform. In 2017, Avast acquired Piriform, and its users have been worried about the bundling of Avast products and promotions.

CCleaner interface

In the past, Piriform’s operations were strictly censored, so users could not disable usage data collection. Even if the user specifies not to update the program automatically, it will force the user to update.

In 2019, Microsoft temporarily banned CCleaner on the Microsoft Community Forum, which resulted in the program’s link being reviewed at the time of publication.

Microsoft community forum ban list

was added to the new threat entry on the Microsoft Security Intelligence site today, and Microsoft now classifies CCleaner as a PUA: Win32/CCleaner threat.

This page does not provide any information on why Microsoft now classifies CCleaner as PUP/PUA, but Microsoft has stated that they do not support registry cleaners, so Microsoft recommends that they should not be used. Some products like

"registry cleaners indicate that the registry requires regular maintenance or cleaning. However, when you use these types of utilities to modify the registry by mistake, serious problems may occur. These problems are due to instability Users may be required to reinstall the operating system. Microsoft cannot guarantee that these problems can be solved without reinstalling the operating system, because the degree of changes made by the registry cleaning utility varies from application to application,” Microsoft noted in its 2018 support announcement.

In addition, Microsoft’s evaluation criteria indicate that displaying "misleading" or "inaccurate" statements about files and registry entries will result in the program being classified as a potentially harmful program. The

software must not mislead or force you to make decisions about equipment. This is considered to limit your choice. In addition to the previous list, software that exhibits a lack of choices may also:

-display exaggerated statements about the health of the device.

- Misleading or incorrect statements about files, registry keys or other items on the device.

- Displays a statement about the health of the device in a shocking way and requires you to pay or take certain measures in exchange for the alleged problem.