back to article DNS lords expose netizens to 'poisoning'

More than a decade after serious holes were discovered in the internet's address lookup system, end users remain vulnerable to so-called domain name system cache poisoning, a security researcher has warned. Developers of the software that handles DNS lookups have scrambled to patch buggy code that could allow the attacks, but …


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  1. brandon

    What DNS servers...

    arent affected by this issue?

    I think thats the key issue here, did BIND clean up their act?

  2. Steven Knox
    Dead Vulture

    I agree with brandon

    The space you wasted telling your audience OF IT PROFESSIONALS that:

    "DNS lookups are one of the most basic and common tasks on the internet. They translate human-friendly names such as with machine-readable IP addresses like"

    would have been much better used with a list or link to a list of affected servers, or of those systems which use real crypto.

  3. Anonymous Coward
    Anonymous Coward

    BIND is one of those with the problem

    Go and read the article again

    This may provide some enlightenment

  4. Sara Peters

    IETF isn't getting it

    If the underlying DNS infrastructure is ever going to change, the Internet Engineering Task Force (IETF) has got to do to more research, create more secure technology and spread the word about it. Then ICANN and IETF both need to force the issue onto the operators of the root servers and top-level domain servers.

    IETF does have a working group just to TALK about security (, but unfortunately they don't seem to be DOING anything.

    It makes a girl want to start breaking kneecaps.

  5. Robert Armstrong
    Black Helicopters

    Lords of the DNS?

    Are these Lords in Parliament?

    Or be they Irish?

    Do they march in parades in the USA on March 17?

    Pray tell...

  6. zcat
    Paris Hilton

    Got it sorted!

    One of our local banks has an interesting approach to the problem.. they set the DNS expiry time to zero so that it's never cached and every lookup has to go back to their server (in Australia)

    Paris, because I suspect even she could spot the flaw in this logic.

  7. Brett


    Well firstly the IETF have been and are doing something (DNSSEC) this protocol is ready to roll (and is being rolled in places) however it does need a push from a political (and marketing) point of view.

    As for the zero cache although this is a good idea in principal if everybody were to ignore the TTL's on zones and there was no caching we would have a helluva lot more traffic on an already very congested internet, so not really scalable.

    The answer is short term to ensure the ID's are propely randomised, and long term to deploy DNSSEC.


  8. Samuel Walker

    Pardon my ignorance, but

    Doesn't the very definition a pseudo-random number generator mean that it isn't ever truly random and thus will always be able to be predicted?

    It may not be easy to predict it, but nevertheless, given enough time you will always be able to predict it.

    Surely then, until they use true random number generators everything will be vulnerable to pseudo-random number prediction.

  9. James Butler

    Money Talks - Users Walk

    @Samuel Walker

    Do you know of any examples of "true" random number generators in the programming world? Or even the distant hope of one?


    Good on ya! Credit where credit is due. Many articles about things like cache poisoning, spamming and other internet-age bugaboos fail to mention what is available to fight the beasties, even as those who are responsible for implementing those solutions (or at least the next generation of potential solutions) ignore them. DNSSEC for cache poisoning, SMTP-Auth for spam. etc.

    When a potential solution will cost real money to implement, the big players avoid adopting it, choosing instead to hope nothing really bad happens or to push responsibility for fending off the problem onto some other player.

    "Users, activate those phishing filters, now with cache poisoning detection technology!"

    "Users, buy our latest anti-spam filter!"

  10. Sara Peters

    Brett's right...

    DNSSEC does qualify as IETF "doing" something.

    I just wish I knew of the root servers and TLDs doing something with DNSSEC. Or perhaps doing something that takes active baby steps toward DNSSEC.

    Is there something I don't know about? Inquiring me wants to know.

  11. Anonymous Coward
    Anonymous Coward

    @Samuel Walker

    What you say here:

    "It may not be easy to predict it, but nevertheless, given enough time you will always be able to predict it."

    .. is of course completely correct. But not all PRNGs are equal, and in practical terms, a crude one that can be guessed in a few hundred to a few tens of thousands of guesses is predictable, whereas a crypto-based PRNG that would require a brute-force attack lasting longer than the likely span of the universe is, to all intents and purposes, not predictable.

  12. Anonymous Coward
    Thumb Up


    Well it looks like good old Nominet is at least trying...

    They have an interesting paper on the problems encountered with widespread use of DNSSEC -

    And a testbed for people to try out their own implementations -

  13. Anonymous Coward


    Yes, there is. DNSSEC was implemented in 2005 at the .se TLD.

  14. Michael

    random versus unpredictable

    The key difference is whether your number generator is designed to produce a good statistical spread of numbers, or if it's designed to be difficult to predict. It's possible to have a random number generator with excellent statistical properties that is highly predictable, or a highly unpredictable generator with terrible statistical properties. The first is good for monte carlo simulations, the latter for cryptography.

    Unfortunately most programmers don't seem to understand the difference.

  15. James Henstridge


    Brett: Up until RFC 5255 was released this year, there were some good reasons not to implement DNSSEC: it provided a means to list all the names that exist in a domain without testing every possibility.

    As well as sending signed responses about existing domains, DNSSEC sends signed responses for domains that do not exist (otherwise you could spoof a "no such domain" response for a real domain). One of the constraints on DNSSEC is that all the response data can be signed ahead of time so that the DNS server doesn't need access to the private key. It'd be impractical to create signed responses for every possible non-existent domain, so the signed negative responses actually assert that ranges of domains do not exist. By enumerating the gaps between the domains, you can discover what domains really exist.

    Given that they only fixed this problem earlier this year (by introducing hashing to the negative responses), it isn't too surprising that it isn't more widely used yet.

  16. Glen Turner


    @zcat: One of our local banks has an interesting approach to the problem.. they set the DNS expiry time to zero so that it's never cached and every lookup has to go back to their server (in Australia)

    Which is exactly why the DNS caches in Australian ISPs set a minimum cache time. We got sick and tired of that bank's DNS server being temporarily unavailable and the blame for the apparent lack of connectivity falling on us ISPs.

    This problem is easily fixed by deploying DNSSEC. It's well time the DNS registries got that happening. DNSSEC isn't suitable for use on all names in a firm, but it's deployment against the DNS names supporting public services would address most of the real-life spoofing problem.

  17. Enno

    Short DNS expiry...

    This is most commonly a sign that the people you are dealing with have a load-balancing/failover product that does DNS redirection from site to site as well as the more common intra site redirection. Its hardly the sort of thing an admin chooses to do for themselves...


  18. RaelianWingnut
    IT Angle

    Random Number Generators

    I suspect that if you google for them, you'll find hardware-based true random numbers which use a natural random noise source like the reverse biased breakdown noise from a signal diode, fed to some analogue to digital convertors. It's not rocket science, but I'd suspect they're used mostly in the intelligence community rather than in the mainstream corporate world.

  19. Ginger


    I think these Lords in particular dance

  20. bert hubert
    Thumb Up

    PowerDNS & Random

    Just to add my two bits. Amit Klein informed us in a very proper manner of our deficient random generator, and was helpful in finding a good replacement. We implemented his suggestion of going to AES in CTR-mode, which appears to work very well.

    I can understand why not everybody goes down this route though - we've already had problems with people being unable to distribute PowerDNS because it suddenly contains 'encryption'.

    DNS is vulnerable enough as it is, even with good random. Bad random is inexcusable. For more details, see

    Bert Hubert

    PowerDNS.COM BV

  21. Anonymous Coward
    Anonymous Coward

    @James Butler

    "Do you know of any examples of 'true' random number generators in the programming world? Or even the distant hope of one?"

    Assuming you're not sticking to 100% software solutions then there are plenty of true random number generators. Most of them are based around devices that sample the background radiation. You can get pretty good results from certain wireless cards that generate a number based on whatever they can pick up.

  22. Steve Kay

    One in a long list

    Aside from the marvels of "unlimited" (but only if it's not much HTTP traffic) "broadband" (as long as you live inside a telephone exchange) and how the connection providers have marketed the interwebtubes, the single biggest tickler is that Joe Public actually believes that this network is in some way secure.

    So much of the underlying system is still run on trust:

    - I trust my peers not to try to obliterate Youtube outside .pk... oops

    - I trust an unknown third party to guarantee my banks web server is my banks web server

    - I trust is really

    - I trust an unauthenticated address translation system to tell me where to connect

    - I trust a badly maintained personal computer with the intimate details of my life

    The list goes on and on. When I tell legal clients that email is not privacy-guaranteed (and more akin to writing your message on a postcard) unless it's encrypted (and even then....blah) they are genuinely shocked, as conventional wisdom presents email as more like letters than postcards.

    Yes, DNS is insecure. So's the rest of it. But don't tell the unwashed masses.

  23. Mage


    50c PIC CPU connected to 5c 3.3v zener diode as a noise source. I2C or serial connection to host.

    (You can get 8pin SM PIC with built in A/D).

    I'd not bother with wireless. Too many non-random signals.

    The noise from a Zener is real random noise from Molecular kinetic/heat energy. The amount is related to temperature. It's usable from DC up to 2GHz as a "white noise" source to align / check filters with a Spectrum analyser.

  24. Brett

    All too aware of dnssec and its shortcomings


    I am well aware of RFC5255 and the problems it fixes, and am very well aware of how dnssec works (I deployed it on the European Reverse tree) hopefully when there are some solid implementations of nsec3 we will start to see more deployments, however we still need support from ISP's and there needs to be a cost benefit for them to do it.

    Sara: You are right the root operators are not/have not done anything with regard to dnssec in . However don't blame them the key and signing policies are political issues that need to come from ICANN, if you really want to see this happen get involved with ICANN and push it through.


  25. Brett


    and i just realised atcually it's rfc5155 not rfc5255.


  26. Anonymous Coward

    Crap song alert!

    DNS lookup wherever you may be

    I am the lord of the dns said he

    And I'll spoof your site, wherever it may be

    'Cause I am the lord of the DNS said he

  27. James Grinter

    Implementing cryptography

    So, the random number generator in BIND is poor, but we can all rest assured that they got it right with implementing DNSSEC?

    Yes... that makes perfect sense.

  28. Stewart Knight
    Paris Hilton


    This problem is going to be made a hell of a lot worse when IPv6 is the standard!

    Time for a radical re-think me-thinks!

    Paris would know the answer!

  29. vahid

    DTLSL ... SSL UDP ?

    Just a thought

    (DTLS) is a protocol based on TLS that is capable of securing datagram transport (UDP for instance).

  30. Ross

    *How* old?!

    Errr, this kind of research was done YEARS ago using phase space analysis. Like 7 years ago. Read up on Michael Zalewskis research at

    It was primarily targetted at TCP hijacking, but DNS was also considered and shown to be vulnerable to the same weakness.

  31. Chris Ellis

    Crypto Cookies

    Instead of random numbers why not use cryptographic cookies, exactly like in Qmail's mailing list manager and the SYNCookies Linux kernel path (Both by DJB)

  32. Anonymous Coward

    Spot on Steve

    No such thing as absolute security, only ever relative to the ability of the attacker and as secure as the weakest link...this DNS poisoning and variants of, has been going on for years... use numeric IPs. Don't assume everything is OK, and that the system will `look after you` - it won't. Keep your eyes open. Do not trust everything (or anything) you see, until you have verified it to the best of your ability. DNSsec might sound super now, but I guarantee in a few months, definitely years, it will be about as secure as a wet paper bag. Be paranoid, do not trust your ISPs or any silly little notions of security or data protection. Research, probe, test... take nothing for a decent Cisco router, or if you can't afford it then flash the firmware of some cheap generic unit to something halfway decent (eg DDWRT for linksys WRT54G units) and lock it down as much as possible using what is available. Audit regularly, reflash regularly.

    Alternatively just pick up a pen and write on paper,or type then print cipher, put it in a sealed envelope and send via private courier to be scanned and unencrypted by recipient- it might take longer, but it's a lot more secure...

  33. Anonymous Coward
    Anonymous Coward

    Hate to be picky

    But the distinction is not human friendly to machine readable.

    Both are machine readable, and well a domain name is perhaps more human friendly, but so is an IP number in many instances.

    A domain name is just what it says on the tin - a name that associates a domain of addresses.

    So a domain name is something like, a fully qualified domain name with host would be and that address would be associated with an IP number. The point is they are separate systems that interface with each other. DNS uses IP for routing, but that is not a fixed requirement. You could theoretically route via DNS and we could forget IP numbers altogether.

    Machine readable and human friendly is not a true distinction between DNS and IP addresses, but it is a common mistake.

  34. Anonymous Coward
    Paris Hilton

    Re: Spot on Steve

    > DNSsec might sound super now, but I guarantee in a few months, definitely years, it will be about as secure as a wet paper bag.

    In that case, I look forward to you presenting you with a couple of Nobel Prizes and the Fields Medal. And with these powers of prediction, you must be able to tell me what the winning numbers will be in Saturday's lotto draw. I need some extra walking around cash to buy some more bling.

    DNSSEC uses cryptographic hash algorithms and public key cryptography to sign DNS data: SHA, MD5, DSA, RSA, etc, etc. If you can guarantee these will be compromised in a few months or years, you must know about a world-shattering breakthrough in number theory.

  35. Anonymous Coward

    Implementing cryptography

    James Grinter asks: So, the random number generator in BIND is poor, but we can all rest assured that they got it right with implementing DNSSEC?

    Two points:

    [1] There's only a 16-bit space for DNS query IDs. [They were invented 25 years ago to help a resolving server match responses to the outstanding queries it had made. Read RFC 1035. They never are and never were meant to provide a security blanket.] This is a fundamental limitation of the DNS protocol. Feel free to rewrite it and reboot the internet.

    Using good entropy sources to generate these is just an example of security through obscurity. It only takes 65535 packets to enumerate the query ID space. Which is trivial. Even if a client or name server uses a truly random data source for these IDs. And of course all bets are off the bad guy can diddle with the DNS query or response while it traverses the net. That said, I'd prefer a good entropy source, all things being equal. But I wouldn't believe that made my DNS servers and clients more secure. Because it doesn't. Get over it.

    [2] DNSSEC generally involves off-line signing and key generation by special purpose tools, not the name server itself. The tools that generate DNSSEC keys use things like /dev/random or /dev/urandom as the entropy source. Not good, but still a whole lot less predictable than truly random data for a tiny 16 bit space. People using DNSSEC generally go for 1024 or 2048 bit RSA keys. And if they're paranoid, they get the key generation tool to use a data source based on some truly random physical property such as radioactive decay or noise from a semiconductor junction. Now these sources could be used to generate query IDs, but the cost/benefit analysis simply isn't worth it. Feel free to buy one for each of your name servers and hack the code to use that device as the entropy source.

    The real solution to this long-standing DNS spoofing problem is widespread deployment of DNSSEC. Anything else is just re-arranging the deckchairs on the Titanic.

  36. Anonymous Coward

    Doing something about secure DNS

    Sara Peters said: I just wish I knew of the root servers and TLDs doing something with DNSSEC. Or perhaps doing something that takes active baby steps toward DNSSEC.

    .se, the Swedish TLD has been signed for a couple of years now. RIPE NCC has signed its zones and Some other TLD registries set up DNSSEC testbeds and have run experiments. If your favourite TLD isn't using Secure DNS yet, complain. Ask them why not. Create a fuss. Encourage them to deploy it and announce a timetable.

  37. Pete Spicer

    Secure DNS

    So the Swedish TLD has signed it - but the TLDs I'd like to know most whether they have been signed are the ones those who are less IT-inclined are going to know: .com, .net, .org

    If they haven't been signed yet, there could be some real problems...

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