Botnets have been in existence for about 10 years; experts have been warning the public about the threat posed by botnets for more or less the same period. Nevertheless, the scale of the problem caused by botnets is still underrated and many users have little understanding of the real threat posed by zombie networks (that is, until their ISP disconnects them from the Internet, or money is stolen from their credit cards, or their email or IM account is hijacked).