Recently, a small bank in Wyoming with a 1 man IT department contracted a nasty computer virus that their antivirus did not catch. The virus caused a huge loss in production and new business.
Because their Big Name antivirus failed to detect the virus, the bank began looking for an alternative. How did this happen? Because today computer crackers (The Bad Guys) are exploiting third party applications such as Java, or Adobe Flash. Also there may be machines on the network with outdated antivirus definitions.