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A SYN/ACK DoS attack that acts by rejecting ACK requests or a Ping DoS attack shouldn't be too difficult to defend against. You should be able to configure your network to react to the easily identifiable type of internet traffic that those attacks rely upon by filtering or limiting that traffic.
A DDoS attack is a much more challenging problem. On the upside, I would think a small business would be a less likely target for a DDoS attack. It would be prudent to make sure that your back-end is separate from your web facing front-end, so impact on your business is limited. To really address the DDoS attacks themselves, you could add network capacity to the point that you are basically running a commercial server farm, but that obviously isn't a realistic option, especially for a small company. You could go with a hosting provider that has that capacity available for you if necessary, and have established procedures for dealing with DDoS attacks.