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.
This family of downloaders use XMLHTTP control to download and ADODB.Stream control to write malware on the vulnearble machine, often combined with some other vulnerabilty that allows the downloader to escape from the Internet Explorer internet zone.
Typically SillyDownloader replaces the Windows Media Player in order to make sure that the downloaded component gets executed.
The downloaded component usually contains an another trojan or a backdoor.
Further information about ADODB control is available from Microsoft at: https://support.microsoft.com/?kbid=870669