As nobody has tackled this one...
The bulk of DOS attacks that actually occur tend to happen irrespective of the victims setup. As long as the victim has a connection to the internet, then they're a possible target.
There is no fix against these type of attacks with the exception of disconnecting from the 'net (or maybe changing IP address if the attack isn't relying on hostname/DNS lookups).
There are a smaller number of DOS attacks that rely on specific security loopholes in various protocols. As SME usually only deals with a small subset of very well known protocols, the chances of being attacked in this way are relatively small.
In short: As much as possible... but no more.
Regards,
Luke