RE: Block access to ports

  • From: "Mike Liddekee" <mliddekee@xxxxxxxxx>
  • To: "[ExchangeList]" <exchangelist@xxxxxxxxxxxxx>
  • Date: Wed, 27 Aug 2003 08:52:17 -0500

It all depends on your setup.  If you're trying to block at the firewall
level, you need to determine what type firewall you're using and its
setup.  Most firewalls (unless misconfigured) should be set up to not
allow any traffic in unless specifically allowed.  If you're running a
router w/ NAT and no "real" firewall, then that's where most people get
burned.  If anyone tells you NAT is a firewall, run the other direction
as fast as you can.  The other way people I know have gotten burned on
the latest bug its that their outer perimeter is great but someone w/ a
laptop goes home, dials up, gets infected, goes back to work and plugs
in.  These types of back doors will kill you every time.  You can block
these ports for this one but the next virus that comes out will require
different ports, the next one will then require different ones, and so
on.  It'll be a never ending game of cat and house.  The thing to do is
to make sure things are locked down on your network to prevent these
types of events and that all the proper systems are in place.  You still
can't guarantee yourself 100% (nothing in IT is 100%) but if you don't
have the systems in place you'll be fighting for days every time a new
event comes out.  When I arrived at my current job we had none of these
in place.  After months of fighting, we now how these things in place
and have had no viruses or Trojans of any type (knock on wood). 




Mike Liddekee

Network Engineer


Humco Holding Group, Inc.

7400 Alumax Dr. 

Texarkana, TX  75501

Ph:  (903) 831-7808 ext 697


-----Original Message-----
From: satish garimalla [mailto:satishgarimalla@xxxxxxxxxxx] 
Sent: Wednesday, August 27, 2003 8:33 AM
To: [ExchangeList]
Subject: [exchangelist] Block access to ports

Hi All,

          I know this is a bit off the topic.But, we are having problems
with the recent virus attacks.We are in the process of eliminating this.

As recommended by symantic web site, Iam supposed to block access to TCP
port 4444 at the firewall level and also block  tcp port 135 "DCOM RPC"
and UDP port 69 , "TFTP"

Can any body explain me how to do this as I am not so familiar with
this.All I want to know is that how to block these ports(from command
prompt ?? or from windows itself  ??) Either may be the case, could you
please explain me the steps in doing so ...

Thanking you very much ,

Satish Garimalla


Narain Karthikeyan. He's fast, really fast. Want to meet him?
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