Zeus is a dangerous malicious application that is aimed primarily at stealing the banking details of targeted users.
It is one of the most widespread and professionally-used malicious applications available today.
There is even a Zeus Builder Toolkit which allows cyber criminals around the world to customize Zeus to provide any functions they want.
Zeus is also known as WSNPoem and PRG among many others.
Zeus Botnet normally reaches a user's system via spam emails that are apparently from legitimate websites.
These emails contain links to malicious websites which will ask the user for their credentials and also tell them to download a particular file.
The file contains a variant of Zeus Botnet, and it gets installed on the user's system.
More recently, social networking websites such as Facebook and MySpace have also been targeted by variants of Zeus Botnet.
These variants send messages to users of these social networking sites claiming that they need to download and install an 'update tool' to update their user profiles.
This 'update tool' of course contains the variant of Zeus Botnet.
Once installed, Zeus waits until the user connects to the internet and downloads a configuration file which contains a list of web banking websites to get the user's information for.
Whenever the user visits a website on the list, Zeus Botnet will initiate a keylogger function and save all the keystrokes of the user.
Zeus also has an agent in the web browser which may also inject false fields into web forms which the user will unknowingly fill, thereby submitting even more personal information to the developer of that Zeus variant.
Zeus Botnet will periodically submit the information it has gathered on the user's web banking activities to the malware developer.
As Zeus is a dangerous program that invades privacy, you should take measures to remove it as soon as you find a copy on your system.
One of the important steps is to conduct a full system scan using genuine antivirus as it can properly detect this type of malware.