Hello Frank

> As I understand it, a firewall prevents computers from communicating
> undesirable communications.  Poorly worded, perhaps, but I am sure it
> addresses the intent of firewalls.
This is partly true, the decision to "accept a communication" depends 
at a firewall on source/dest (ip) , Protocol ( tcp etc) and port 
This is ofcourse a simplification.
But the package filter that is build in leaf doesn't look at the content 
of a message. 
(so if a webserver is allowed to pass, it passes indepent if this is a 
scientifc information or a advertisement for uh cars.)
Content filtering is done by other programs, (f.e. junkbuster,squid 
etc).

> I get lots of undesireable communications on my telephone.  There seems
> to be a marketing industry devoted to using my phone number as a sales
> tool.  I am sure everyone on the reflector can identify with this
> plague. 

Now to your telephone,
If you want to block certain protocols (fax f.e) this is built in most 
telephones.
 if you want to block connections depending on their origin ( src 
telephonenumber ) this can be done only if the src-telnr is 
transmitted. In different countries this is done. In Germany this is 
done on a voluntary base, so as soon as somebody wants to stay 
unrecognized he will block this feature.
In that case you could "blacklist" notorious callers or reject all but a 
selected group of numbers. 
Programms like that are build in in almost any mobile telephone and 
home telephone switch.
To filter on the content is almost impossible
It takes for you, with a higher intelligence as your computer, even 
some time to detect that the message the caller is telling you is not 
interesting for you. 
To build a speach recognition and interpretation is far beyond a lrp 
box ;) 

> Getting to the point, has anyone every considered building a firewall to
> prevent this abuse?  A telephone firewall.  Could something of this
> nature be implemented on an LRP box?  A rethorical question because I
> know it can be implemented. I would do that but don't know how. My lack
> of knowledge extends to the programming.  I am pretty sure I can handle
> the hardware requirements.
What can be done in my opinion is filtering for special numbers or 
only allowing authorized callers, for example with a "telephone login"
After connecting to a box, they hear a message please enter your 
telephone code. 
If they have that wrong, the connection is broken
But that would prevent any person with honest intention to contact 
you.
A simpler method is useing the display with the telephon number and 
your decision to take the phone. 
But all that demands that the calling number is transmitted, which 
isn't always true.

 
> The question is, does anyone know of any efforts to do this?
no 
> 
> My Dachstein firewall is on all the time, connected to my cable modem.
> It could just as well be handling telephone traffic on the same 24/7/365
> basis.
And  for a lot of other interesting applications,  
secureing your home
printserver
makeing coffe ; ) 
but remember lots of applications means drilling holes in your 
firewall.

Anyhow, I like thought experiments :) 

Regard
Eric Wolzak
member of the bering crew


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