Ant,
In the words of
HHGG ,
Don't Panic 
The risk of exploitation has
up to now been relatively small. (By relatively here I mean we're trusting the staff at MS and EEYE et al not to exploit the head-start they've had on the problem; but we're also assuming that nobody else has discovered this or it somehow hasn't leaked out. There's no evidence of this yet) So up to now, there's a reasonable chance that thise weakenss hasn't been exploited.
HOWEVER this is all about to change. Now that the details of the vulnerability are out, there are going to be people trying to exploit it. The good news is that
there IS a patch. It's
essential that people apply it. My big concern over local software firewalls, which I didn't get over very well in my first post [I may go back an try and re-work it] is that people who
think that because they have a firewall and therfore are not as diligent in applying the patch, could come seriously unstuck
A security maxim is "defense in depth" which is just another way of saying "don't put all your eggs in one basket". You need up-to-date patches, anti-virus softwar
and a firewall to keep you systems secure...
One security consultant puts it like this:
A firewall defined:
A device which explicitly controls network access to your computer network.
A device which allows you to monitor the type of traffic passing in and out of your network and react accordingly.
A firewall is not:
A complete security management strategy
A guarantee of security
A power base
