Rootkit:W32/Necurs is a standalone malware that was first seen in 2011, but gained more prominence once it started being used in the Gameover Zeus botnet.
Based on the settings of your F-Secure security product, it will either move the file to the quarantine where it cannot spread or cause harm, or remove it.
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 updates
First check if your F-Secure security program is using the latest updates, then try scanning the file again.
Submit a sample
After 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 scanning
If 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.
Rootkit:W32/Necurs is a kernel-mode driver component that can be used by an attacker (or added as component to another malicious program) to perform unauthorized actions to take control of an operating system, without alerting the system's security mechanisms.
According to published research, the Necurs rootkit was incorporated in late 2014 into the Gameover Zeus botnet as a protective mechanism, preventing attempts by the user to remove the malware from an infected machine. The addition of the standalone Necurs rootkit to an existing threat operated by another party (and analysis of the rootkit's code, which appears to be suitable for such use) has lead to it being considered 'crimeware for hire'.
More details and commentary about this malware is available at: