In the past few months many people got their computers infected when opening an attachment received from friends in their contact lists. Once infected your computer starts sending the same virus to the people in YOUR contact list without you even being aware of the fact!
How to remove the virus once you've been infected:
1.
Download Malwarebytes’ Anti-Malware and install it on your computer.
2. Reboot in safe mode.
3. Run a complete scan using Malwarebytes’ Anti-Malware.
4. Once the scan is finished click “Show Results” to display all objects found.. Hit OK then click the Show Results button. Click the Remove Selected button.
5. Restart your computer.
Now your computer should be clean!