Last year, 24 million computers using the Microsoft security were attacked by malware that steals all kinds of information from the computer. Only 5 million or less were actually affected by the attack and information was stolen.
The attack is related to the malware such as Gamarue, Dorkbot, Zbot, Banker, Bancos and Fareit for example to steal login information for online banking usernames and passwords for different websites, keys for signing digital codes and other data. If Microsoft Security Essentials or Windows Defender detected informational stealing malware on the computer of the victim, the software will prompt the user to change their passwords on the computer.
In a period of 6 months the warning for the Zbot malware is show at least 260.000 times to users. The users affected this malware and changed their passwords were happy they received this alert, according Deepak Manohar from Microsoft.