North American Network Operators Group
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Re: zotob - blocking tcp/445

  • From: Shane Amante
  • Date: Mon Aug 15 22:06:40 2005 
Chris,

This isn't directed at you, just adding my 2 cents to the thread ...

On Aug 15, 2005, at 3:29 PM, Christopher L. Morrow wrote:

On Mon, 15 Aug 2005, [email protected] wrote:

NetBIOS was never meant to be a WAN protocol, so no problem
in blocking it.

rule #1: do not be the Internet's Firewall
rule #2: see rule #1

That should definitely be on a T-shirt.  :-)
a leaf network can make any decisions they want on traffic filtering,
large ISP's should probably not do this as there are invariably people out
there that will want SNMP/ICMP/NetBIOS/SQL-NameService to work over their
WAN link(S). I recall some 'fun' with this issue on:

1) slammer worm (ms has a developers thingy that REQUIRES 1434 to work
over the internet)
2) welchia/nachi - how can I ping monitor my remote sites?

ymmv.
Leaf network filtering (or not) is largely solved. Keep in mind, some SP's sell "Managed Security Services," which may be PE- or CE- based firewalls, but run by the SP on behalf of the customer. If the customer cares enough, then ask and/or pay the SP to block the traffic they don't want, only on their access circuit(s). Presumably, the SP will figure out a model for the service to both instantiate and maintain the filter(s) as well as recoup costs for backhauled bits that get dropped at, or near, the doorstep of the CE. (Note, the word "model" could mean an additional charge above & beyond basic access or it may be included as part of basic access -- it all depends on how much work, sophistication in filtering, etc. occurs as well as what the market can bear).

In this case, one size (a.k.a.: filtering) does not (easily) fit all ...

-shane