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Security The Internet

Network Attacks Via DNS 147

Posted by timothy from the operator-please dept.
Iphtashu Fitz writes "Without DNS the internet wouldn't be all that useful. Despite being a ubiquitous part of the internet it is overlooked by many as a potential security hole. At this weekends Defcon 12 conference in Las Vegas, security researcher Dan Kaminsky warned that DNS can open up seemingly secure networks to attack. Because most firewalls and other security devices treat DNS requests as harmless it provides an excellent conduit for transferring covert data in and out of otherwise protected systems. At Defcon, Kaminsky demonstrated some software that allows a server to act as a communications hub using DNS. This let him transmit instant messages and even audio streams over an encrypted connection carried by spoofed DNS requests."

"Because the data looked like typical DNS traffic it wouldn't be detected or logged by firewalls or intrusion detection systems. He also pointed out that monitoring DNS could help in other unrelated ways: because the recent MSBlast worm did lookups on windowsupdate.com infected machines could have been detected by simply monitoring DNS server logs."
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Network Attacks Via DNS More

Network Attacks Via DNS

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  • TCP or UDP (Score:3, Interesting)

    by rf0 ( 159958 ) <rghf@fsck.me.uk> on Sunday August 01, 2004 @06:57AM (#9857143) Homepage
    I have to wonder what protocol they used as DNS does allow for both UDP and TCP (TCP when the messages is over 512 bytes IIRC)

    Rus

    • Re:TCP or UDP (Score:5, Informative)

      by Anonymous Coward on Sunday August 01, 2004 @07:01AM (#9857157)
      An interesting property of DNS is that there are servers all over the net which will happily relay your message. Even if your only connection to the net is through application level proxies, you probably have a local DNS resolver. That's all you need. No packet has to traverse the firewall directly.

      They may have used spoofed DNS packets just to bypass a firewall, but information can also be tunneled in real DNS packets, so even if you only allow DNS to/from certain servers, you're still not safe from this leak.

      • Re:TCP or UDP (Score:5, Interesting)

        by digitalhermit ( 113459 ) on Sunday August 01, 2004 @07:51AM (#9857254) Homepage

        They may have used spoofed DNS packets just to bypass a firewall, but information can also be tunneled in real DNS packets, so even if you only allow DNS to/from certain servers, you're still not safe from this leak.

        Yup, and that's not the half of it. With the extensions being duct-taped onto the existing spec it makes it easier and easier to do this. I've seen some hacks to allow all sorts of arbitrary information to live on the servers, some relayed automatically because of the extensions, some used to modify how mail servers respond, some even for routing. It's nothing new (remember transferring data via ICMP ECHO?) but it's on a new level now.

        KL
        • I cringe when someone proposes bolting their latest P2P or broadcast hack to DNS every week. Willy-nilly adding extensions to working protocols is almost always a bad idea. It's like giving Murphy a free kick.
    • I'm sticking to 512byte DNS for now, as the goal is to show proxied connectivity (i.e. evading mere filters is too simple).

  • Old news (Score:5, Informative)

    by fred87 ( 720738 ) <mailNO@SPAMfredemmott.co.uk> on Sunday August 01, 2004 @06:58AM (#9857149) Homepage
    nessus has been pointing this out as a security hole in it's scan results for at least 3 months now...

    • Re:Old news (Score:3, Informative)

      by fred87 ( 720738 )
      Here's a link:

      http://cgi.nessus.org/plugins/dump.php3?id=11580

      • Re:Old news (Score:3, Informative)

        by Anonymous Coward

        Here's a link:

        http://cgi.nessus.org/plugins/dump.php3?id=11580

        And here's a clickable hyperlink (you may have seen these before):
        http://cgi.nessus.org/plugins/dump.php3?id=11580 [nessus.org]

        Seriously, it's not that hard! In Slashdot all you have to do is put <URL: at the start and > at the end.

    • And I've been bitching about SPF using DNS TXT records for longer than that. Don't people firewall their DNS anymore? If your inside a network and your trying to leak info out, DNS is the best way to do it.
    • Actually...no.

      Dan is literally *using* DNS to hide his traffic, not just using udp:53.

      I know Dan and he's one of those people crazy (smart) enough to hack on something as dumb as this long enough to get something interesting out of it.

      -davidu
      • Dan is literally *using* DNS to hide his traffic, not just using udp:53.

        Even so, this still isn't that interesting. So you mime encode it (or whatever), tack on a domain, and talk to a rogue dns server. Anyone dealing with secure networks should know that having any opening to the internet is a security risk and take that into account when designing one's network.

    • Re:Old news (Score:3, Informative)

      by Effugas ( 2378 )
      Recursive lookup support isn't required to achieve incoming connectivity (see induced lookups), and being able to do lookups against the outside world isn't identified by anyone as a risk.

      --Dan
    • SO... is there any chance of developing a distributed, secure DNS implemenation that is backward-compatable?

      Right now, we rely on 13 servers to run DNS, why not 26? Why even have root name servers at all? Could we develop a DNS system ala Usenet, that sends updates both up and down stream... And then just have the ability to slowly or quickly accept new incoming information as true based on various criteria, to avoid having bad information flooding the DNS servers?

  • This is supposed to be 'news'? (Score:5, Informative)

    by fw3 ( 523647 ) * on Sunday August 01, 2004 @07:01AM (#9857155) Homepage Journal
    Layering services over dns has been a discussed topic in books / seminars for at least a decade already.
  • This story seems quite similar to a previous one about using DNS for communications, from LayerOne. Incredibly stupid to use for mainstream communications, but perfect for hackers, with low data requirements, anyway.

  • So does this mean (Score:4, Funny)

    by foidulus ( 743482 ) * on Sunday August 01, 2004 @07:03AM (#9857160)
    That is should change my bookmark to http://66.35.250.150 [66.35.250.150] now?

  • In other news... (Score:3, Funny)

    by Zorilla ( 791636 ) on Sunday August 01, 2004 @07:04AM (#9857162)
    ...Microsoft plans to release a security update to Windows XP which will secure the DNS hack. For all future internet usage, please enter in http://216.239.57.99. It's not a bug, it's a feature.

  • 90% of the internet is valnerable ... (Score:4, Interesting)

    by after ( 669640 ) on Sunday August 01, 2004 @07:04AM (#9857163) Journal
    to somthing called DNS poison [google.com]. Why? Because system administrators are anal and fail to realize that software like BIND is not written to be secure. Hell, DNS was not even designed for such a large internet. The original DNS implementors were bad programmers and designers.

    BIND9... don't get your hopes up. The BIND company sells paches for their software. Meaning that if you don't pay them money then you're going to be running an errornouse DNS server.

    Still most people use BIND for two reasons: no one wants to learn the crusty details of DNS and 2) Linux comes with BIND as it's default name library.

    Alternative like djbdns [cr.yp.to] should be used.

    • Re:90% of the internet is valnerable ... (Score:3, Interesting)

      by Anonymous Coward
      ufortunately, djbdns is not open-source. Until a true open source alternative to BIND appears, we're stuck with it.
      • >ufortunately, djbdns is not open-source.

        Incorrect, it is open source.

        It isn't GPL.

        There's a big difference.

        >Until a true open source alternative to BIND appears, we're stuck with it.

        By "true alternative" do you mean it has to be GPLable?

        Get real. djbdns' source is 100% available for you to look at and patch to your hearts content. If you find an error, send a fix to DJB and he'll add it after review. He'll even give you $500 [cr.yp.to] as a reward for your hard work. Find me a GPL program that makes an offer like that.

        Now, if he doesn't like your patch, you can post the patch on the internet. You can even put it alongside the source. You can even make an autopatch program that will patch djbdns during make so that dumb users can handle the process

        For the disbelievers, here's [cr.yp.to] the source code.

        Here's [cr.yp.to] bernstein's statement about the freedom of his software. Feel free to print it out and sign it if you're insane on the idea he can revoke your license.

        • Re:90% of the internet is valnerable ... (Score:2, Informative)

          by Anonymous Coward
          That's what people call "shared source". Open Source requires that you can distribute modifications of the source. Bernstein doesn't allow that, so consequentially djbdns is not Open Source. This may or may not make it less valuable to you, but don't lie about the facts to lure others into misevaluating the situation.
          • Thanks for posting that so I wouldn't have to :) It's sad to see that many people seem to think availability of source code equals Open Source, when the term is clearly defined by the Open Source Initiative. If we tolerate this, Microsoft will have an easy going convincing people that Open Source doesn't matter since they have "Shared Source" already. You have the source, right?
        • "Now, if he doesn't like your patch, you can post the patch on the internet. You can even put it alongside the source. You can even make an autopatch program that will patch djbdns during make so that dumb users can handle the process"

          Can you make binaries of your new program and distribute them? If not, I can't see how you call this open-source. It cuts off all of the distributors from carrying patched versions that work with their own distribution, instead of whatever way that djb wants.

        • $500 is nothing. (Score:2, Informative)

          by warrax_666 ( 144623 )
          The $500 guantee is worthless. How many hours do you think it takes to audit the djbdns source code? Anything more than 50, and you'd only need to make $10 an hour at your current job to make it a very unprofitable way to spend your time.

          (Also: Who judges the "entrants" for the $500 prize? That's right, DJB does, and there are no formal rules as to exactly what qualifies as a security bug).
          • No, it is worth something. If his software wasn't secure, offering the guarantee would have been an extremely arrogant move. DJB is arguably enough of an asshole that I suspect that there are numerous people who would go out of their way to find security holes in his guaranteed software, just to spite him.
            • No, it is worth something. If his software wasn't secure, offering the guarantee would have been an extremely arrogant move.
              Guess what? DJB is extremely arrogant (as many clever people tend to be).

              DJB is arguably enough of an asshole that I suspect that there are numerous people who would go out of their way to find security holes in his guaranteed software, just to spite him.

              You failed to answer my point about who gets to judge the "entrants" and the rules of the contest.

              Look, it's a simple matter of

              • You failed to answer my point about who gets to judge the "entrants" and the rules of the contest.

                It's irrelevent to my contradiction of your statement, "The $500 guantee is worthless."

                Look, it's a simple matter of economics: Auditing code is mostly tedious and there are sufficiently many ways of earning much more money (and with a guaranteed payoff!) auditing code that no amount of spite is worth it.

                One matter of economics you're not considering is that value and worth are not equivalent to monetary

        • >ufortunately, djbdns is not open-source.
          Incorrect, it is open source. It isn't GPL. There's a big difference.

          The point being made is that djbdns is not open in some pretty important ways, like allowing other people to extend it for example.

          Bernstein is a total control freak, he demands that people install and use his code in very specific ways...

          • Incorrect, it is open source. It isn't GPL. There's a big difference.

            Yes, but the trolls [trollse.cx] have redubbed anything to which you can read the code "Open Source." It confuses the argument, but it makes PHB's feel better about using software not developed by a money-grubbing company (the kind they were taught to like while they were earning their MBAs).

            DJB's software is Open Source. It is free-as-in-beer, not free-as-in-speech, perhaps. That said, just because something is Free Software does not make it sup
            • DJB's software is most definitely NOT Open Source. It violates point 4 of the definition here [opensource.org], which states:

              [...] The license must explicitly permit distribution of software built from modified source code.[...]


              The DJB license does not do that (and even prevents modified source distribution). End of story.
              • You miss my point -- the whole "Open Source" movement clouds the definitions. OSI embraced the original APSL, which in many ways was more restrictive than the DJB licenses.

                There are many things that are open source and not free. DJB's stuff. Quite a bit of UW mail software, etc. etc. You can't distribute a patched version of pine, either, without UW's permission.

                OSI obfuscates these issue because the trolls don't get along with RMS.

                • You miss my point -- the whole "Open Source" movement clouds the definitions. OSI embraced the original APSL, which in many ways was more restrictive than the DJB licenses. There are many things that are open source and not free. DJB's stuff. Quite a bit of UW mail software, etc. etc. You can't distribute a patched version of pine, either, without UW's permission. OSI obfuscates these issue because the trolls don't get along with RMS.

                  Actually, the definition of "open source" used by OSI (launched

            • the parent post that started this all was quick frankly trolling. bind9 was a complete rewrite from the ground up. I don't recall the last time I had an exploit in bind9. I have had multiple openssl and openssh vulnerabilities in the past year however.

              So as I have told many people, every network app is going to have its issues. Some have more than others, but with proper patch management (and despite the original posters claim, you don't have to pay for BIND patches) you can keep your network secure.

              A

        • Incorrect, it is open source.

          Incorrect, it is not open source. You cannot distribute modified versions. And 'modified versions' in his case means so much as having the binaries installed in a different location than they would be by building and installing his source distribution... among other things. You can only redistribute a djbdns package if the effects of installing your package on a system are exactly the same as the effects of installing his official source distribution.

          Because of it not being

        • Incorrect, it is open source. It isn't GPL. There's a big difference.

          Yes, there is a big difference, and djbdns is not Open Source. It violates points #3 and #4 of the Open Source Definition [opensource.org]. (It also doesn't comply with the DFSG [debian.org] which is why Debian has it in non-free.)

          I quote:

          3. Derived Works

          The license must allow modifications and derived works, and must allow them to be distributed under the same terms as the license of the original software.

          4. Integrity of The Author's Source Code

          The l

        • Get real. djbdns' source is 100% available for you to look at and patch to your hearts content. If you find an error, send a fix to DJB and he'll add it after review.

          "Available Source" !== "Free Software".

          You can't redistribute changed, patched DJBDNS. You can't fork it if you figure something requires a fundamental change in design philosophy. You cannot distribute binaries. DJB release a new version every millenium or so - so when you set up Qmail or DJBDNS, you spend a week applying patches and testi
        • You can even make an autopatch program that will patch djbdns during make so that dumb users can handle the process

          Assuming that people have compilers, make, etc. on their production servers ... but you did say "dumb users". ;)
        • Please read at least the first line of the Open Source Definition [opensource.org]:

          Open source doesn't just mean access to the source code.

          Note that opensource.org invented the term "open source" - it was not in use to describe software until they had that meeting where they invented the term - so they certainly get to say what it means.

          DJBDNS is "disclosed source". Big difference.

        • Until a true open source alternative to BIND appears, we're stuck with it.

          By "true alternative" do you mean it has to be GPLable?

          Not necessarily. Being distributable wouln't hurt, though. Being compatible with the DNS standard would also be a plus. Don't get me wrong, I am all for alternatives to BIND, but djbdns cannot even be distributed as a simple rpm or deb package not messing the whole bloody filesystem, for God's sake.

          If you want a name server with such a strong emphasis on security

      • Take a look at PowerDNS
        http://www.powerdns.com/products/powerdn s/
    • Bind9 isn't vulnerable to that. Heck, I doubt even bind8 was.. sounds like a pretty lame attack.

    • Re:90% of the internet is valnerable ... (Score:3, Informative)

      by Anonymous Coward
      No doubt you'll be on +5 informative soon for this 15 year old information.

      BIND hasn't been vulnerable to DNS Poisoning since about version 4.8 unless you set it up allowing external updates from 0.0.0.0 (have to be specified as they're not allowed by default).

      And djbdns is about as useful as a condom machine in the vatican for anyone needing more than a dns cache for a LAN.
    • As the AC above states, BIND hasn't been vulnerable to DNS poisons for many years.

      Because system administrators are anal and fail to realize that software like BIND is not written to be secure.
      Not sure why you say this, ISC have released a constant stream of patches since BIND was released and every announced security hole has been fixed. Not only that but they even added options to chroot the daemon and run it as an unprivileged user. They also have links on its homepage to guides on how to chroot the e
    • stop spreading fud. They do sell support contracts. The patches are freely available. In fact check out their security matrix. It lists all the known problems, versions effected, and suggests a patch or upgrade to get.

    • BIND9... don't get your hopes up. The BIND company sells paches for their software. Meaning that if you don't pay them money then you're going to be running an errornouse DNS server. [original emphasis]

      Still most people use BIND for two reasons: no one wants to learn the crusty details of DNS and 2) Linux comes with BIND as it's default name library.

      Alternative like djbdns [cr.yp.to] should be used.

      I wish it was so simple. There are two most important problems with djbdns, though. Namely:

      1. unlike BIND, d
    • And this has to do with what exactly? Others have ripped your issues with BIND to shreds so I don't need to comment on it. However, nothing in the article discusses BIND and afaik Mr. Kaminsky's hack is going to work with *any* DNS server. If his claims are right and the packet is crafted to look kosher than any DNS server is going to forward it. Even your precious djbdns.

  • helpful (Score:5, Funny)

    by Scythr0x0rs ( 801943 ) * on Sunday August 01, 2004 @07:12AM (#9857177)
    some good people could break into the nameservers of a large ISP such as AOL and send out spoofed NS records for update.windowsupdate.com or whatever it is and deploy linux to all windows users.

    Warning: this update may require a reboot.

  • This is why.... (Score:3, Insightful)

    by Cylix ( 55374 ) on Sunday August 01, 2004 @07:25AM (#9857196) Homepage Journal
    I've set control lists for DNS for a long long time.

    After the IP over DNS tunnel came out... it was actually a bit necessary. Our staff would do anything to get out of doing work...
    • I've set control lists for DNS for a long long time.

      Could you explain in laymans terms what this is/how it works?
    • I've set control lists for DNS for a long long time.

      The use of ACLs is not secure because an atacker may spoof easily the IP address.

      Is a good way , yes, but not the ONLY and FINAL way to protect our networks.
      • an atacker may spoof easily the IP address.

        For what values of easily? (i.e. UDP or TCP?)

      • Yeah, you could proxy DNS and use source address verification. Still, the installation this wasn't a problem.

        We were actually limiting access from the internal to external network. So, all DNS requests were only allowed to a target server. (Our servers of course).

        Specifically, this was implemented to prevent IP over DNS so users couldn't get passed the firewall.

        Yeah... it's stupid we had to police our own staff . If people were doing their jobs... they could have had their fun too. However, this was not

  • Suspicious? (Score:3, Insightful)

    by timgoh0 ( 781057 ) on Sunday August 01, 2004 @07:37AM (#9857218)
    Wouldn't large amounts of DNS traffic look suspicious? Especially if they originated from one machine.

    • Re:Suspicious? (Score:2, Interesting)

      by Anonymous Coward
      I don't think so. I would assume a normal user browsing the net (especially sites with lots of ads) and sending 4-5 emails (without using a relaying proxy) generates quite a bit of DNS traffic.

      I think it may be worth the firewall's while to check if the DNS packets are in the right format - for example if the domain name in the request is ghjj!!&^ then one should frown ! I don't what kind of load this would mean for the firewall, though.

      (I type this even as I recover from the nausea, vomitting and sic
    • Wouldn't large amounts of DNS traffic look suspicious? Especially if they originated from one machine.

      Only if someone or something is checking for it.

  • Cheating Wireless networks (Score:5, Insightful)

    by technothrasher ( 689062 ) on Sunday August 01, 2004 @07:40AM (#9857225)
    I've noticed in the past that many of the public wireless networks that want you to pay to use allow DNS traffic to flow even before you've paid. I've often thought that'd you could use that to build a tunnel and not have to pay for service.

    Mind you, I've never done it because it would be kind of rotten, but it did cross my mind.

    • You are right, I know people who do that when they travel through international airports. It doesn't work that fast (something like a 36k modem) , but it is free. AFAIK you do need a domain and a DNS server you control yourself.
      • Why do you need the domain?
        • not quite sure: but you can probably only connect to the local DNS (caching) server on the WLAN. DNS requests are forwarded to the server that is responsible for a certain domain. So to route the DNS packets (with other traffic encapsulated in it) to your DNS server, you need a domain... I guess ...
        • Why do you need the domain?

          The local wireless Domain Name Server will only accept DNS requests, and will only give you DNS replies.

          So you create bogus DNS requests pointing to various places on your domian. But they aren't real places on your domain - they are encoded data. The wireless service doesn't know the answer to your DNS request, so it forwards the request to the domain to get the answer - it forwards the request to your domain. You configure your domain to decode your bogus DNS requests into g
    • Yep....

      A while ago...

      People were dialing up to MSN's 800 service (the number your system dial's before you have an account) and DNS was completely open.

      Thus spawned IP over DNS. There was a previous slashdot story concerning this. Free dial-up provided you had a modified DNS server.

      Neat huh.

    • You probably could, but that can easily be foiled, if that kind of behaviour becomes commonplace.

      All the wireless network admins have to do is forward all DNS packets to a DNS server that only allows you to look up a specific domain, and block everything else.

    • IP Tunneling Through Nameservers [slashdot.org]. And you can apparently stop that [seclists.org] too, but I doubt it's very efficient unless you whitelist domains unauthenticated clients can look up.
  • my standard iptables rules only allow some ISPs dns-servers.
    • my standard iptables rules only allow some ISPs dns-servers

      And then those ISP's dns-servers relay those messages to the hackers DNS server... The downside is that every packet that goes out has the destination server's domain name marked on it.

  • Misleading Title (Score:1, Informative)

    by Anonymous Coward
    The title of the post is misleading. DNS can't be actually used to attack a network, only to slip sensitive data by firewalls.

  • Harmless? (Score:5, Insightful)

    by jjeffrey ( 558890 ) <`slash' `at' `jamesjeffrey.co.uk'> on Sunday August 01, 2004 @08:12AM (#9857294) Homepage
    I don't think that networks allow DNS because it is harmless, but because it is necessary, that's an important distinction.

  • So? (Score:1)

    by jbb999 ( 758019 )
    If you can send data in any form you can tunnel anything you like over it. Why is this news?
    • I have a protocol which sends data in Morse code by short and long delays in accessing the same web page over and over again. ;)
  • Surely we all know that "DNS" comes at the top of the list of the Internet's vulnerabilities? Tunneling data; many bugs in DNS software over the years; vulnerability to DOS: Surely we all know this already - why is this news?

    DNS was an afterthought - but it seems to me a very necessary one, and one we will have to continue to live with.

  • That's why you use proxies! (Score:5, Informative)

    by wowbagger ( 69688 ) on Sunday August 01, 2004 @08:38AM (#9857396) Homepage Journal
    That is why any GOOD sysadmin will set up the system so that there is a single DNS server for the plant, and that server and that server alone is allowed to send and receive DNS packets to the greater Internet - all other machines are to use the local DNS server.

    Not only does this GREATLY reduce the amount of DNS traffic a shop produces (by caching all requests locally) it helps prevent this sort of foolishness by requiring all packets to be well formed DNS packets - else the server drops them.

    Then, you can block any client that makes more than a few requests a second.

    Yes, it is easier to set up a firewall to be very porous to outbound traffic, but it is more secure to deny all direct access, and force clients to run through proxies for the various services.

    • Doesn't work that way (Score:3, Insightful)

      by Fished ( 574624 )
      The packets in question are (or at least could be) well formed.

      Imagine that I own ISpy.com, and a user does a lookup on "user.jsmith.passwd.12345.ispy.com". Your server, in the middle, will forward that request to the NS for ispy.com more or less unchanged. And it doesn't have to be this obvious - it would certainly be easy enough to come up with some form of steganography appropriate to use in DNS.

      Not that proxies are a bad idea, but in this case proxies will not prevent the attack. Mostly, they'll

    • Yeah, check out the slides. I rather obsessively follow the spec (limit to Base32 my upstream queries, Base64 my downstream TXT records, though I could just as easily use Base32'd CNAME's or MX's).

      The whole point is that DNS is equivalent to every web server proxying, and that this proxy service does have security implications.

      But please, cache stuff locally :-) It makes my radio hack work much much better.

      --Dan
    • Gosh, I even went so far as to state, very clearly, that a key part of defeating this sort of thing was, and I quote my previous post, "block any client that makes more than a few requests a second."

      Now, lets see. DNS packets are limited to 512 bytes per spec (and having just finished implementing an DNS client the spec is quite clear in my mind). Let us take the commonly used value of "less than ten" for the term "a few".

      So, you have less than 5120 bytes/second of throughput. That's assuming that you don
  • There was an old slashdot story [slashdot.org] eons ago about people using DNS tunnels to abuse the free dial up lines used for setting up a dial up ISP account. Covert comms over DNS is nothing new, but oddly it doesn't seem to have ever caught on.
  • Hi,

    I've read somewhere that there are some "implicit" rules in the Firewall 1 default configuration that let DNS through anyway.
    Is that true ? I have the eval CD here, but haven't had the time and the resources to test it.

    cheers,
    Rainer

    • Re:Firewall 1 lets through DNS by default ? (Score:1, Informative)

      by Anonymous Coward
      Yes, for default installation only
      It is quite simple and SHOULD be turned off

      It is a mere matter of unchecking one box and setting up explicit rules for your local DNS server to comminicate to its external DNS resolovers

  • Duh... (Score:5, Funny)

    by blixel ( 158224 ) on Sunday August 01, 2004 @09:34AM (#9857607)
    That flaw in most firms' network security leaves a vulnerability that can be used by hackers to sneak intellectual property outside a company, communicate with a compromised server inside the company,

    In other security news alerts, there was a major hole disocvered in SSH. It turns out if a hacker installs a rogue SSH daemon on the server, he can do nefarious things with it.

    • Re:Duh... (Score:4, Informative)

      by Effugas ( 2378 ) on Sunday August 01, 2004 @04:36PM (#9859558) Homepage
      Most trojans need to poll the outside world periodically, to determine whether they have a new set of operations to execute. With this approach, no polling is necessary -- there's an open pipe _into_ the organization, and the trojan can remain perfectly silent.

      --Dan

  • "without DNS" = LDAP (Score:4, Interesting)

    by Anonymous Coward on Sunday August 01, 2004 @09:56AM (#9857709)
    Note that LDAP is fully capable of doing host name resolution, there's even an RFC for it (AFAIK the one that specifies how to store POSIX user info also specifies how to store host names).
    And in fact, DNS can be used for user details via Hesiod.

    Both LDAP and DNS are hierarchical federated database systems. Personally, I find current LDAP implementations to be more manageable, better designed, and generally nicer (can set very fine grained permissions) than current DNS implementations. A name system based on LDAP rather than DNS would be fully feasible and IMHO as or more globally scalable.

    But we must distinguish between DNS-the-protocol and DNS-the-implementations - It would be possible to have the same piece of software answer both DNS and LDAP queries from the same database. Hey, hello Microsoft Active Directory! But MAD is nasty for other reasons - so where are the Open Source projects to provide a slapd plugin for DNS protocol lookup to openldap databases? It should actually be pretty simple, maybe it's so simple no-one is interested hacking on it....

    • The DNS P2P-server/client system has been proven to be reliable, supporting the unified Internet namespace continuously for hundreds of millions of concurrent users, for many years. Regardless of the techniques used, can LDAP claim that kind of bulletproof track record?

  • How about this : OpenVPN over UDP port 53 ie. DNS (Score:5, Interesting)

    by anti-NAT ( 709310 ) on Sunday August 01, 2004 @10:02AM (#9857747) Homepage

    Thought of this almost two years ago. Run OpenVPN [sourceforge.net] over UDP port 53. I figure a fair number of firewalls may not analyse UDP DNS traffic to see if it actually is UDP DNS traffic. Haven't had a chance to try it out though.

    Thinking big picture, you realise that once opportunistic IPsec becomes available, and with IPv6 it will be, any device in the network trying to interpret traffic, such as firewalls and proxy servers, will become just about useless.

  • nstx (Score:2)

    by cosmol ( 143886 )
    I saw this story through google news and I thought, "better check slashdot." Got an article from 2000.

    http://slashdot.org/article.pl?sid=00/09/10/223024 2&tid=95 [slashdot.org]

    and the current version of nstx:http://nstx.dereference.de/nstx/nstx-1.1-beta 5.tgz [dereference.de]

    • Re:nstx (Score:3, Informative)

      by nutznboltz ( 473437 )
      I was poking around the the FTP site that has nstx and I noticed migr. It's a hack to migrate processes between systems. The migration is not completely transparent to the migrated process since it will lose filepoint locations at least. It appears to reload the migrated process by installing it as a SEGV handler with signal stack and then unmapping most of the loader causing a segfault which starts the migrated process.

  • Quick Summary: What's New (Score:4, Informative)

    by Effugas ( 2378 ) on Sunday August 01, 2004 @04:16PM (#9859470) Homepage
    OK, let me repeat.

    Throwing arbitrary data in DNS -- NOT a big deal.

    Even doing network tunneling over DNS -- ALSO not that big a deal; NSTX has been doing this for a while.

    DNS radio is new. By segmenting audio into small chunks, we actually get universal caching of the streaming signal -- a functionality we've never really had before. Generally, audio broadcast over the Internet falls apart after a few thousand users. Based on this ring-buffer-into-BIND architecture, combined with the utterly minimal bandwidth load of Speex, we should be able to host audio for a much greater number of listeners.

    The entire suite of incoming attacks to firewalls are also new. DNS trusts the hierarchy to tell it the next hop to its target name; since I can acquire second level domains in the hierarchy for minimal cost, it's trivial for me to insert arbitrary destinations along the DNS route path. In technical terms, whenever a recursing resolver comes to my name server to resolve a name, rather than providing an answer, I can redirect that request to another, supposedly authoritative server. That server can be at any address -- even one I cannot IP route to -- but if the resolver communicating with me can route to that address (say 10.0.1.11) my communication will reach that host. If there's an SSH over DNS daemon running on 10.0.1.11, I've now achieved incoming connectivity to the network of my choice, completely bypassing firewalls and a trojan's need to poll.

    Recursion on dual hosted interfaces is not even necessary. There are large numbers of applications that, upon receiving untrusted traffic, execute DNS name lookups. Most commonly, they are reverse PTR lookups, but occasionally there are other types (MX from mail servers, most notably) that can be easily induced. When they are induced, the hierarchy is followed. When the hierarchy is followed, the attacks previously discussed start working. In practice, this means an IDS triggers the DNS server to start proxying traffic between an external attacker host and an internal trojaned machine. Nasty.

    There's some other stuff -- check out the slides and the code -- but long story short, there's some new stuff out :-)

    --Dan
  • are more of a problem than covert channels. Every cell phone is a covert channel out of a business. Since DNS can't be used to deliver advertisements, I don't see a business threat here. It may be a concern to a military installation though.

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