Dasher.B is a worm that exploits a vulnerability in Microsoft Windows Distributed Transaction Coordinator (MS05-051).
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.
The worm's dropper installs the following files:
The file svchost.exe is the actual worm main file. SqlScan.exe is a port scan utilty and SqlExp.exe is a component that is used in MSDTC exploiting.
The worm may also create the following files:
These files are used in exploiting.
The worm scans for systems vulnerable to MSTDC (MS05-051) through TCP/1025. It constructs random addresses using a fixed list of A-class networks. If it finds a system responding to TCP SYN scan, it sends the exploit payload. The payload connects to remote address and waits for instructions. At the time of this writing, the server instructs the infected system to download and execute the worm's dropper and keylogger.
Please see the following page for detailed information on the vulnerability:
https://www.microsoft.com/technet/security/Bulletin/MS05-051.mspx