Intego's Netbarrier product has a problem with the decoders HWC uses in that they are written in a language called Python and are external to the main application. Netbarrier doesn't seem to be able to cope with this at all. Luckily Paolo Cordone figured out a work around as detailed below.

This workaround has been tested on an eMac running10.3.5. Other system versions might have a different Python version/path.

Paolo writes;

I think I have been able to find a workaround for the annoying NetBarrier issue.
In the Antivandal section of NetBarrier

I have added to the Applications list

The following file:

<drive name>/System/Library/Frameworks/Python.framework/Versions/2.3/bin/python2.3

Which seems to be a 'document'

rather than a proper Unix Executable File, such as python proper:

I have not seen the pesky alert anymore :-)