And the most frightening part is that your own computer might be spreading the virus without you knowing it.
On Friday, cyber sleuths from Microsoft and several financial service companies got court permission to tap into tens of thousands of computers located in Pennsylvania and Illinois to look for one specific rogue computer.
Microsoft digital crimes attorney Richard Boscovich is working on the problem.
"You have to find that needle in a haystack and go ahead and start collecting evidence," he said.
Boscovich is looking for evidence the computer was controlling a botnet. A botnet controls armies of computers infected by a malicious software. It operates secretly and remotely under the control of cyber criminals. It spreads the malmare using spam, malicious ads, social media attacks and by other botnets with a specific virus. Zeus installs keyboard recording software onto your computer, so whatever you type, it's secretly sent to cyber criminals.
The Zeus malware can compromise websites that have access to your personal information, such as banks. When you sign on on a normal website, its going to ask you for your user name and password. But on the compromised website, it also asks you for your ATM pin. If you enter that information, it's sent off to criminals who are most likely working overseas.
The good news is that you can remove a botnet from your computer by running ant-virus software.