Bonjour Stephane, Fermer les resolveurs ouverts ne résout pas le problème des DDoS amplifiés par DNS. Le jour où il n'y aura plus de serveur récursifs sur Internet (et ce n'est pas demain la veille), les attaques se feront sur les serveurs autoritaires.
Il est plus facile de construire une liste de serveurs autoritaires que
d'open-resolvers!
La bonne solution c'est BCP-38 (rfc3704).
Cordialement,
Florent
PS:
Fermer les resolveurs ouverts, oui; mais pour différentes raisons:
- "least privilege"
- cache poisoning
- cache snooping
On Sun, 2013-04-07 at 21:59 +0200, Stephane Bortzmeyer wrote:
> Compte-tenu du danger de ces résolveurs ouverts, dénoncé depuis
> longtemps
> <http://www.bortzmeyer.org/fermer-les-recursifs-ouverts.html>
> <http://www.rfc-editor.org/rfc/rfc5358.txt>, et récemment illustré par
> l'attaque contre Spamhaus/Cloudflare, ce travail est l'occasion de se
> livre à une chasse aux résolveurs DNS ouverts sur votre
> réseau. Indiquez votre numéro d'AS à l'auteur et il vous indiquera les
> adresses dangereuses chez vous.
>
> ---------------------------
> Liste de diffusion du FRnOG
> http://www.frnog.org/
> MHTML Document attachment (Open Resolver Dataset Update)
> > -------- Forwarded Message --------
> > From: Jared Mauch <ja...@puck.nether.net>
> > To: NANOG Group <na...@nanog.org>
> > Subject: Open Resolver Dataset Update
> > Date: Sun, 7 Apr 2013 13:46:14 -0400
> >
> > I've continued to update my dataset originally posted about two weeks ago.
> > Please take a moment and review your CIDRs which may be running an open
> > resolver.
> >
> > I've exposed one additional bit in the user-interface that may be helpful.
> > Some DNS servers will respond with RCODE=0 (OK) but not provide recursion.
> > nearly 90% of the servers in the database provide recursion.
> >
> > Some raw stats are also available via the 'breakdown' link on the main site.
> >
> > If you operate a DNS server, or have an internal group that does, please
> > take a moment and review your networks.
> >
> > If you email me in private from a corporate address for your ASN, I can
> > give you access to a per-ASN report.
> >
> > Due to a change in methodology, I have increased the number of servers
> > observed from 27.2 million to 30.2 million hosts.
> >
> > 2013-04-07 results
> >
> > 30269218 servers responded to our udp/53 probe
> > 731040 servers responded from a different IP than probed
> > 25298074 gave the 'correct' answer to my A? for the DNS name queried.
> > 13840790 responded from a source port other than udp/53
> > 27145699 responses had recursion-available bit set.
> > 2761869 returned REFUSED
> >
> > In addition, please do continue to deploy BCP-38 to prevent spoofing
> > wherever possible. I know at $dayjob we have been auditing this and
> > increased the number of customer interfaces that can not spoof.
> >
> > - Jared
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