Sometimes we think we're covered with our backup plan. However, if you have a connection that is connected at all times, you could be at risk. There is a virus called CryptoLocker that could take advantage of your situation. When it gets into your computer, it encrypts your data. Then it asks you for $300 to receive the unencryption method. The virus attacks not only the data on your computer's drives, but also the backup folders if they are connected. It would be horrible to lose both sets of data, wouldn't it?
There is no shortage of hackers out there. Be prepared for an attack.