Windows Defender is flagging CCleaner as a Potentially Unwanted Application


Posts: 8,486   +104
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Why it matters: Are you using the free version of CCleaner? If so, you’ll probably notice that Windows Defender is now flagging the junk file remover as a Potentially Unwanted Application (PUA) after Microsoft recently updated its antivirus program.

CCleaner optimizes a system by removing unused and temporary files, thereby making it faster and freeing up storage space. It also features a registry scanner for invalid references. You can download CCleaner here and see similar alternatives.

Back in 2017, Piriform, the UK-based firm behind CCleaner, was acquired by Avast for $1.3 billion, which has led to other programs being bundled in with the app, including Avast Free Antivirus, AVG Antivirus Free, Google Chrome and Google Toolbar.

It seems Microsoft has taken exception to the bundling of these programs. In a new threat entry, the Redmond firm has classified CCleaner as a PUA. “While the bundled applications themselves are legitimate, bundling of software, especially products from other providers, can result in unexpected software activity that can negatively impact user experiences,” states the notice.

“While the CCleaner installers do provide an option to opt out, some users can easily inadvertently install these bundled applications.”

Microsoft previously stated that it does not support registry cleaners, advising that such programs should not be used.

In Microsoft’s entry on how it identifies malware and potentially unwanted applications, it notes that PUAs are not malware but software must not make misleading claims about a device’s health, files, or registry entries.

Only the free version of CCleaner is being identified as a PUA as it contains the bundled software. Piriform told BleepingComputer that it is in talks with Microsoft to stop its program being flagged by Defender, which is also flagging other Piriform software such as Recuva.

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Posts: 5,469   +6,157
They have a point, why should CCleaner come with the crap it's supposed to clean?

Apparently they've even tried doing it without permission before, as originally reported by TechSpot:

As far as bundles go, chrome is pretty harmless. They do need to pay the bills after all. TechSpot comes with ads too you know. You can block them but you can't opt out of them.


Posts: 29   +12
As soon as I saw the Ccleaner name, I thought that's the company Piriforms product that had been hit with a supply chain attack. It was a crypto mining malware they were hit with to be precise. Windows only.


Posts: 317   +153
Who still uses registry cleaners?
They were of dubious worth back in 9x kernel days when the registry might create performance problems. But now? Not worth the hassle with all their false positives.
I used Norton's version way way back in the day, then wasted a whole day fixing all it's "optimizations". It's like RAM defraggers, a waste of time...

So in the end good for MS. Now if they'd stop flagging actually useful programs like Magic Jellybean, or DDU we'd be golden. Either that or actually ignore them when I tell defender that the programs are okay...


Posts: 13,141   +6,439
These Cleaner Apps are all Malware.
Before Avast bought out Piriform, I would have argued with you. Now I'm not so certain. I never have trusted anti-virus software makers.

At least now I don't have to worry about CCleaner installing Chrome on my PC. To me Chrome is unwanted more so than Avast. Any software that bundles opt-out software should be labeled as PUP.

Edit: I see in the image above I'm wrong about Chrome not being bundled. Doesn't change the rest of my comment though.