CCleaner hack affects 2.27 million computers, including yours?

Your device may have CCleaner malware. Here's what you need to know.

Alina Bradford CNET Contributor
Alina Bradford has been writing how-tos, tech articles and more for almost two decades. She currently writes for CNET's Smart Home Section, MTVNews' tech section and for Live Science's reference section. Follow her on Twitter.
Alina Bradford
2 min read

CCleaner on Android wasn't affected.

Alina Bradford/CNET

Computer-optimization software is supposed to keep your computer running smoothly. Well, in this case, maybe not so much. Monday, the company that makes CCleaner, Avast's Piriform, announced that its free software was infected with malware. If you use CCleaner, here's what you need to know.

What does the malware do?

It gathers information like your IP address, computer name, a list of installed software on your computer, a list of active software and a list of network adapters and sends it to a third-party computer server. Your credit card numbers, social security number and the like seem to be safe.

"Working with US law enforcement, we caused this server to be shut down on the 15th of September before any known harm was done," said the company in the announcement

Who was infected?

According to information provided by Avast CEO Vince Steckler and Consumer Business CTO and EVP Ondrej Vlcek, the compromise to the system may have started as early as July 3, prior to Avast buying the company. The compromised version of CCleaner software was then released to customers on Aug. 15.

Around 3 percent -- roughly 2.27 million computers -- used the infected software. Specifically, computers running 32-bit Windows 10 . If that applies to you, don't panic. The company believes that they were able to disarm the malware before any harm was done. 

How do I know if I have the corrupted version?

The versions that were affected are CCleaner v5.33.6162 or CCleaner Cloud v1.07.3191 for 32-bit Windows PCs. The Android version for phones doesn't seem to be affected. As of Sept. 19, Avast says that 730,000 users are still using the affected version.

If you've updated your software since Sept. 12, you should be OK. This is when the new, uncorrupted version was released. Also, if you have the Cloud version, it should have automatically updated itself by now to the clean version.

I don't use the cloud version. What should I do?

CCleaner v5.33.6162 does not update on its own, so if you use the non-cloud version you may have the corrupted software. Piriform recommends deleting your current version and downloading a clean version from its website.

After you have your new software downloaded, run a check on your system using malware protection software to be sure that CCleaner didn't leave any nasty invaders behind.

Editors' note: This article was originally published Sept. 18 and has been updated with new information.