Firewall Wizards mailing list archives
Re: RE: Why blocking bogons buys you nothing (Mikael Olsson)
From: Mikael Olsson <mikael.olsson () clavister com>
Date: Sun, 09 Nov 2003 19:07:10 +0100
Stephen Gill wrote:
I'd like to point out a few issues with your report as I tend to disagree with it :).
Argumentation good. Shoot.
] Why Blocking Bogons Buys You Nothing This title is misleading. [...] I think you mean to say: "Why Blocking Inbound Bogons Buys You Very Little on Firewalls"
Indeed. I added the "Inbound" clause to the title of http://www.clueby4.org/pubs/blocking-bogons.txt
Blocking Bogons buys you a LOT, you just don't get to see the benefits because others are doing it for you.
Actually, don't you mean egress spoofing protection here? That's a totally separate issue.
So why are we drawing global conclusions from a _single_ site?
Because from what I've seen, that's pretty much what everyone else is doing in when it comes to bogons :) This MAN has about five or six thousand public IPs, spread out over five or six disjoint spans. It's got plenty of people that are likely to attract DDoS attacks (IRC weenies), and indeed, they do happen. It's not the uunet backbone, but, in my opinion, it's representative enough for my target audience.
Many DDOS attacks I see still use random spoofed sources. Most DDOS attack data points to bogon filtering having a _significant_ impact on reducing the overall load reached on the target network.
40-50% is not "significant" for a DDoS in my opinion. Especially not if you're doing it on the wrong end of your Internet connection.
] Blocking the 0/8 network, 127/8 network and 224/3 networks is another ] thing altogheter; there are firm technical and security reasons for ] doing that. There are other networks that will never be part of the global Internet routing table, such as but not limited to RFC 1918 space.
Yes, but the technical reasons are not the same. - 0.* is good to drop because of dumb software that assumes that if the first byte of the IP address is 0, it's uninitialized or otherwise has a special meaning - 127.* is good because lots of dumb software think that packets sourced from 127.* couldn't have come across the network - 224.* and up is good because you don't want to end up sending responses to multicast addresses that end up getting forwarded to thousands of hosts/routers
[... snip lots of argumentation related to me not putting "inbound" in the title. It's there now.]
-- Mikael Olsson, Clavister AB Storgatan 12, Box 393, SE-891 28 ÖRNSKÖLDSVIK, Sweden Phone: +46 (0)660 29 92 00 Mobile: +46 (0)70 26 222 05 Fax: +46 (0)660 122 50 WWW: http://www.clavister.com _______________________________________________ firewall-wizards mailing list firewall-wizards () honor icsalabs com http://honor.icsalabs.com/mailman/listinfo/firewall-wizards
Current thread:
- RE: Why blocking bogons buys you nothing (Mikael Olsson) Stephen Gill (Nov 09)
- Re: RE: Why blocking bogons buys you nothing (Mikael Olsson) Mikael Olsson (Nov 09)
- Re: RE: Why blocking bogons buys you nothing (Mikael Olsson) Barney Wolff (Nov 10)
- Re: RE: Why blocking bogons buys you nothing (Mikael Olsson) Mikael Olsson (Nov 10)
- RE: RE: Why blocking bogons buys you nothing (Mikael Olsson) Stephen Gill (Nov 11)
- Re: RE: Why blocking bogons buys you nothing (Mikael Olsson) Barney Wolff (Nov 10)
- Re: RE: Why blocking bogons buys you nothing (Mikael Olsson) Mikael Olsson (Nov 09)