This is a generic detection for the Brontok Worm. The Brontok worm has been around since 2005 in one form or another. Most variants have the ability to disable security software and participate in DDOS attacks.
This is the generic detection for a worm that has the capability to harvest and forward login credentials from affected systems.
Malwarebytes can remove Worm.Passwordstealer without further user interaction. However, users are recommended to determine which credentials could have been stolen and change them as soon as possible.