O Windows Defender, native antivirus from Windows 10, is pointing to CCleaner as “potentially unwanted software”. The computer cleaning and maintenance app is an extremely popular tool, but it has been characterized as unwanted by Microsoft’s system protection.
This block is not alarming: Microsoft Defender — as it was renamed after the 2004 update — notifies users of the presence of unwanted programs even if it finds no signs of malicious activity. However, the warning informs you that the program could be the result of some unwanted installation.
According to Microsoft, “some free installers and promotional distributions may come bundled with other apps, including apps that are not required by CCleaner or produced by Piriform.” Therefore, CCleaner was configured as one of those unwanted elements.
“Although the extra applications are legitimate, […], especially products from other providers, they can lead to negative user experiences.” Bleeping Computer.
Automatic installers are the problem
In the same dialog, Microsoft described that the problem lies in how easily these programs are installed together with the expected software. Software like Google Chrome, Google Toobar, Avast Free (and other apps that adopt the method) easily go through the installation process.
For Microsoft, “some users can easily install the app bundle without noticing.” Therefore, even if there is an option to deny the bundled download, it is not displayed well in the installer.
Later, Avast, owner of Piriform, the company that develops CCleaner, said that they “are already in contact with Microsoft to understand why CCleaner becomes ‘potentially unwanted software’. We assume that the issue is related to the combo and we believe we have already resolved this, so that our product is no longer classified as such”.
Therefore, if you already have the latest version of antivirus and are a CCleaner user, the Microsoft Defender notification should not appear. Otherwise, please be aware that the optimization app poses no risk to your computer.