Summary
This detection identifies compromised installers for the CCleaner utility program, which have been altered to include a backdoor that silently runs in the background when the affected installer is launched.
The affected files are detected by F-Secure security products with the latest database updates as Trojan.PRForm.A and Backdoor.Agent.ABXS. Instructions on how to check if your F-Secure security product is using the latest database update are available in Community: How do I know that I have the latest updates?.
Removal
Based on the settings of your F-Secure security program, it will either automatically delete, quarantine or rename the file or application, or ask you for a desired action.
Mitigation
Users are also recommended to update their CCleaner software to version 5.34 or higher. According to news reports, an automated update to the CCleaner Cloud version has addressed the issue for that version.
A False Positive is when a file is incorrectly detected as harmful, usually because its code or behavior resembles known harmful programs. A False Positive will usually be fixed in a subsequent database update without any action needed on your part. If you wish, you may also:
- Check for the latest database updatesFirst, check if your F-Secure security program is using the latest updates, then try scanning the file again.
- Submit a sampleAfter checking, if you still believe the file is incorrectly detected, you can submit a sample of it for re-analysis.Note: If the file was moved to quarantine, you need to collect the file from quarantine before you can submit it.
- Exclude a file from further scanningIf you are certain that the file is safe and want to continue using it, you can exclude it from further scanning by the F-Secure security product.Note: You need administrative rights to change the settings.
Technical Details
Supply chain compromise
- Piriform: Security Notification for CCleaner v5.33.6162 and CCleaner Cloud v1.07.3191 for 32-bit Windows users
- Talos Intelligence: CCleanup: A Vast Number of Machines at Risk
- Wired: Software Has a Serious Supply-Chain Security Problem
The backdoor's payload
- Computer name
- List of installed software
- List of running processes
- MAC addresses of the first 3 network adapters
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