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 detection database 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.
The NjW0rm worm can spread via malicious file attachments to spear phishing email messages, though it is more notable for spreading via infected removable drives, on which the malicious components are hidden and the only visible presence is a specially crafted shortcut .LNK file (which is detected as Worm:W32/NjW0rm). If the user plugs in the infected drive and clicks the LNK file, the worm's malicious file is launched.
Once NjW0rm is active on a machine, it can serve as a backdoor. Among other actions, the malware can steal passwords (including reportedly from No-IPs dynamic DNS service), contact a remote command and control (C&C) server and execute instructions from the remote attacker and update its own configuration.
To continue spreading, the worm looks for and infects any other removable drives connected to the infected machine.