Firewall Wizards mailing list archives
Re: ICMP Packets.
From: "Perry E. Metzger" <perry () piermont com>
Date: Wed, 03 Jun 1998 12:26:39 -0400
"Don Kendrick" writes:
I've never understood why blocking ICMP was going to make you more secure in the first place. Lots of ICMP information is very valuable in making protocols run smoothly. Sure, some of it can be dangerous if it is misused, like redirects, but you should know what you are doing, not blindly block the whole protocol.My main reason for doing it over a year ago was that I did not want anyone mapping my external network as well as redirects.
If you are filtering datagrams that claim to come from your network that originate externally, redirects are not an issue. They also can be individually filtered. Most of the external networks for the firewalls at my clients aren't exactly hard to guess the map of, btw. -- router, set of bastion hosts connected to it by a hub. If someone is going to figure out something interesting based on knowing that, I've made a giant error in my design already.
But it also has been helpful in blocking some of these more recent attacks as well.
Which "some of these more recent attacks" would those be?
I run ICMP internally and also think it should be run externally, I just don't think they should be mixed.
IP is an end to end protocol. ICMP is an integral part of IP. If you allow IP through a network device, you have to allow ICMP to follow it. Perry
Current thread:
- Re: ICMP Packets., (continued)
- Re: ICMP Packets. Perry E. Metzger (Jun 02)
- Re: ICMP Packets. Alec Muffett - SunLabs (Jun 02)
- Re: ICMP Packets. James R Grinter (Jun 02)
- Re: ICMP Packets. Henry Hertz Hobbit (Jun 03)
- Re: ICMP Packets. Don Kendrick (Jun 02)
- Re: ICMP Packets. Perry E. Metzger (Jun 02)
- Re: ICMP Packets. Perry E. Metzger (Jun 03)
- Re: ICMP Packets. Bennett Todd (Jun 04)
- Re: ICMP Packets. Paul D. Robertson (Jun 05)
- Re: ICMP Packets. Don Kendrick (Jun 02)
- Re: ICMP Packets. Perry E. Metzger (Jun 03)
- Re: ICMP Packets. matthew green (Jun 04)
- Re: ICMP Packets. Bennett Todd (Jun 04)
- Re: ICMP Packets. Darren Reed (Jun 05)
- Re: ICMP Packets. tqbf (Jun 07)
- Re: ICMP Packets. Darren Reed (Jun 07)
- Re: ICMP Packets. blast (Jun 08)
- Re: ICMP Packets. Aleph One (Jun 09)
- Re: ICMP Packets. Perry E. Metzger (Jun 03)
- Re: ICMP Packets. Ge' Weijers (Jun 05)
- Re: ICMP Packets. Bennett Todd (Jun 05)
- Re: ICMP Packets. tqbf (Jun 04)