On January 25th a new backdoor known as Sadhound has been spammed in emails with subject 'I Miss You'. Sadhound is not a worm and does not spread by itself.
Depending on the settings of your F-Secure security product, it will either automatically delete, quarantine or rename the suspect file, or ask you for a desired action.
More information on the scanning and removal options available in your F-Secure product can be found in the Help Center.
You may also refer to the Knowledge Base on the F-Secure Community site for more information.
Sadhound drops a text file in Windows Temp folder and opens it with Notepad. The text looks as follow:
There's no special reason for sending this to you, except that... I was feeling a little lonely, and when I asked myself what I seemed to be missing the most, the answer turned out to be ...you. I Miss You
F-Secure Anti-Virus detects Sadhound with the existing updates as a dropper.