The scale of the threat posed by cybercriminals has been revealed after researchers took over a network of computers for 10 days, gaining unrestricted access to thousands of bank and credit-card accounts.
They showed how a botnet, a network of 180,000 compromised or zombie computers, allowed thieves to steal thousands of bank account and credit-card details and computer passwords and to spy on the browsing habits of the users.
In an unprecedented insight into how "botnets" operate and how lucrative they can be, security researchers at the University of California, Santa Barbara, estimated that they could have sold the information that they collected for more than $8 million on the thriving underground market for stolen data.
There are thousands of separate botnets operating around the world — many bigger than the Torpig botnet that was hijacked by the UCSB Department of Computer Science reseachers who took control from its cyber-criminal creators in January by setting up a server to intercept communications from zombie machines.
The hijack lasted 10 days before the botnet's controllers updated their system.