Re: Should ISPs be blocking open ports for their customers?

[Stephen Perciballi <stephen.perciballi () ca mci com>]

It's not really common practice for transit type providers to do this.
The networks are typically engineered to forward packets and not filter
them.  Hopefully the providers have dedicated staff to handle abuse.  In
that case issues should be handled on a case-by-case basis.

> From my experience that includes ingress filtering from abusive customer
networks, Null or blackhole routing offending customer IPs at the nearest
edge, and sometimes egress filtering traffic destined for a customer
network.

The other issue is that there are people who will actually use the
services on their WAN which will just generate another kind of complaint
:).

________________________________________________________________
Stephen Perciballi              phone: 1-416-216-5141
Internet Security Specialist    cell : 1-416-877-1808
MCI                             pager: sperciba-pager () ca mci com
www.mci.com/ca                  24/7 : 1-888-886-3865

On Mon, 8 Sep 2003, nonleft wrote:

> is it common practice that ISPs are inspecting the TCP headers?
> What is the sense of it all when everybody upgrades to IPv6 or uses IPSec?
> is it sensible for fast routing?
>
> At 09:03 08.09.2003 -0400, you wrote:
> > This white paper was just published today by SANS:
> >
> > Internet Service Providers: The Little Man's Firewall?
> > http://www.sans.org/rr/special/isp_blocking.pdf
> >
> > A large percentage of malicious traffic is focused on a small number of
> > vulnerabilities and their associated ports[1]. Blocking some of these
> > ports will isolate infected machines and slow the spread of malicious,
> > autonomous code such as worms. However, the vulnerable services used by
> > these worms do have legitimate uses. If secured properly, they can be
> > used without the risk of infection. In this paper, we focus on ISPs that
> > provide Internet access to consumers. This paper assumes that a consumer
> > is a home user or a small business without dedicated IT staff. This
> > paper does not apply to backbone infrastructure providers or co-location
> > providers.
> >
> > In part of this paper, we argue for blocking ports commonly used for
> > Microsoft File sharing and related services; specifically, ports 135,
> > 137, 139, and 445. These ports and, in particular, Microsoft File
> > Sharing, draw a lot of attention from malware authors.
> >
> > ...
> >
> > _______________________________________________
> > Full-Disclosure - We believe in it.
> > Charter: http://lists.netsys.com/full-disclosure-charter.html
>
> ___________________________________
>
> kind regards
> nonleft
>
> "the early bird catches the worm,
> but it is the second mice that gets the cheese!"
>
> _______________________________________________
> Full-Disclosure - We believe in it.
> Charter: http://lists.netsys.com/full-disclosure-charter.html

_______________________________________________
Full-Disclosure - We believe in it.
Charter: http://lists.netsys.com/full-disclosure-charter.html