From: david_laporte at harvard.edu (David LaPorte)
Subject: SQL Slammer - lessons learned

> 135-139/TCP/UDP to be open to the Internet?  How about port 445/UDP?

That should read 445/TCP

> No, you wouldn't, because DNS servers talk on port 53, and they wouldn't
> negotiate port 1434 because it's reserved for SQL.

By blocking 1434/UDP you run the risk  of block a small number of DNS queries. 
Anything above 1023 is fair game.

David


On Wednesday 05 February 2003 10:38, Paul Schmehl wrote:
> On Wed, 2003-02-05 at 06:55, John.Airey@...b.org.uk wrote:
> > How the ports are managed by the ISPs is up to them. We have a managed
> > router where we block everything we can without breaking legitimate
> > access. However, not having a practical option to block certain ports is
> > a problem. My point was on the allocation and use by TCP/IP stacks.
>
> Can you think of a legitimate reason why ISPs should allow ports
> 135-139/TCP/UDP to be open to the Internet?  How about port 445/UDP?
> Many ISPs now block port 25/TCP (for obvious reasons.)  Why not other
> service ports?  What about the ISPs whose policy it is to not allow
> customers to run servers?  Why should they allow any traffic at all from
> the service ports?
>
> > Sure, you can block 1434 udp inbound, but what if your DNS server (that
> > doesn't run SQL server) picks that port randomly for incoming data from
> > other DNS servers? You'll get failures when you shouldn't.
>
> No, you wouldn't, because DNS servers talk on port 53, and they wouldn't
> negotiate port 1434 because it's reserved for SQL.

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