Dridex is a virus that will reside in the memory of your computer rather than the hard drive. It sleeps, waiting, until you log in to your banking institution and then using Form injection, screen scraping and key-logging it sends your banking information to the bad guys.
This new variant is delivered in the form of a MS Office .doc file with embedded macros. The macros load the virus from compromised websites.
Make it the rule of thumb to never open an email attachment from an unknown sender!
Turn off macros in Microsoft Office if you don't need them. If you don't know what they are, you don't need them.