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Cambridge Breached the Great Firewall of China

Posted by Zonk on Tue Jul 04, 2006 12:06 PM
from the didn't-work-against-the-mongol-spammers-either dept.
Security Government Education The Internet Politics
Darren Rayes writes to mention a ZDNet article on Cambridge academics' claims that they have breached the great firewall of China. They also claim that by misusing the firewall they can launch DDoS attacks against IP addresses behind the wall. From the article: "The IDS uses a stateless server, which examines each data packet both going in and out of the firewall individually, unrelated to any previous request. By forging the source address of a packet containing a 'sensitive' keyword, people could trigger the firewall to block access between source and destination addresses for up to an hour at a time."
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[+] Comcast Forging Packets To Filter Torrents 413 comments
An anonymous reader writes "It's been widely reported by now that Comcast is throttling BitTorrent traffic. What has escaped attention is the fact that Comcast, like the Great Firewall of China uses forged TCP Reset (RST) packets to do the job. While the Chinese government can do what they want, it turns out that Comcast may actually be violating criminal impersonation statutes in states around the country. Simply put, while it's legal to block traffic on your network, forging data to and from customers is a big no-no."
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  • Submit details! (Score:5, Funny)

    by Anonymous Coward on Tuesday July 04 2006, @12:10PM (#15656672)
    With enough people working on it, we can temporarily block the entire country from the rest of the Internet. How's that for a fourth of July?

  • Legal action against Cambridge? (Score:5, Insightful)

    by zanderredux (564003) * on Tuesday July 04 2006, @12:11PM (#15656677) Homepage
    Isn't Cambridge deliberately creating an opportunity for the Chinese government to prosecute them?

    What about those inside China using those exploits for legitimate ends?

    Is Cambridge indirectly helping the Chinese government to fix firewall issues?

    Are Cambridge researchers after fame at the expense of the freedom of the Chinese people?

    • six of one... (Score:5, Insightful)

      by Armchair Dissident (557503) * on Tuesday July 04 2006, @12:59PM (#15656850) Homepage
      ...half a dozen of the other.

      Certainly TFA suggests that the DoS attack could be used against chinese government computers, but this could also be used against chinese citizens. An exploit is, after all, an exploit. So I would suggest that in the case of the DoS attack, reporting it to the appropriate people - in this case the Chinese authorities - was the right thing to do.

      Unfortunately, in this case, the very flaw that allows a DoS against machines within China also permits those inside the firewall to ignore the resets sent back, so by reporting the DoS, they've also reported how the censorship can be circumvented. (or, by discovering the censorship circumvention they've unfortunately stumbled upon a DoS attack).

      In this case, I really don't think that there is a One True Answer.

      • Re:Legal action against Cambridge? (Score:3, Funny)

        by Anonymous Coward
        The University of Cambridge is an English university, not an American company, you (obligatory) insensitive clod!

        (It's "obligatory" because it's the only way insightful anonymous coward comments get modded up.)

      • Re:Legal action against Cambridge? (Score:5, Informative)

        by CaymanIslandCarpedie (868408) on Tuesday July 04 2006, @12:34PM (#15656764) Journal
        Cambridge would leap off that cliff as well by helping China to further block any ways for citizens to bypass the firewall and obtain information about "sensitive" topics. It really bothers me that so many in the U.S. who claim to value freedom so much (who are out blowing up fireworks today to celebrate such - fireworks mostly bought from China I might add), will help a country who values freedom so little.

        FYI, Cambridge isn't a U.S. university.
        • Not that it's at all relevant, but Cambridge is very buddy buddy with MIT

          http://www.cambridge-mit.org/cgi-bin/default.pl [cambridge-mit.org]

          /Just showing that they both have very smart technical people learning/researching there.

          • How in the name of @#$(@$#* is knowing how to circumvent the great firewall going to do any good if you don't tell anyone about it.

            This is not helping China. They know how their firewall works, they built it. They also know where Cambridge University is (unlike half the readers of Slashdot).

            Slashdot is helping China by bringing the article to their attention.

            This has been circulating in the security blogs for a week now. There are basically two schools of thought. One is that we might fix the IP stac

          • Part of valuing freedom is valuing Chinese self-governance. It's not freedom if we step in and replace it every time someone disagrees with us. Banging the drum and screaming freedom is not a good reason to go tell the Chinese they're running their own country wrong. That's what self-important plutocrats and warmongers who need justifications behind which to hide do.

            Believe it or not, even America has to say "wow, China, you get to run your own country today" once in a while.

      • They're supposed to be helping them (Score:5, Interesting)

        by Anonymous Coward on Tuesday July 04 2006, @01:08PM (#15656875)
        I'm presenting a paper on Ignoring the Great Firewall of China at the 6th Workshop on Privacy Enhancing Technologies being held here in Cambridge this week. It turns out that this censorship system works by sending reset packets to each end of the connection, rather than blocking packets. If they don't dutifully close, but just discard the packets, the firewall is completely ineffective. More about this in the paper and in my security group blog posting. [http://www.cl.cam.ac.uk/~rnc1/]

        Their research is concerned with DRM ass hat tactics and such...pity!

      • Re:Legal action against Cambridge? (Score:4, Informative)

        by mrogers (85392) on Tuesday July 04 2006, @04:00PM (#15657393) Homepage
        This paper was presented at the Privacy Enhancing Technologies Workshop [petworkshop.org], alongside with papers about Tor [eff.org] and Mixminion [mixminion.net]. I'm pretty confident that the authors aren't trying to help the Chinese government. What they are doing is embarrassing the Chinese government, presenting it with a difficult choice between dismantling its firewall and suffering DoS attacks, and publicising a method of circumventing the firewall. By using the normal channels for vulnerability disclosure, the authors protect themselves from politically-motivated accusations of "cyberterrorism".
      • I think the point they're trying to show that information censorship is useless, and creates more security problems than it prevents. In addition, cheap solutions won't work. If China want's real censorship, then the very least we can do is force them to spend buco bucks on it, or force them into an all or nothing situation. Like it or not, China needs connectivity to the rest of the world more than the rest of the world needs connectivity to China.

        China also has a very "wall" orientated culture. Someb
          • Incidentally, there are more Cambridges in the US than in the UK

            Er. No, there's exactly one of each over 10k people in each [wikipedia.org] nation [wikipedia.org]. Of course, since Cambridge in this context isn't a city at all, and since there's essentially nobody who actually thinks of MIT when someone says Cambridge who has even a passing familiarity with universities, this is essentially moot.

            at least one of which is also notable for its large univerity. Used to confuse the fuck out of me, for one.

            Probably because you're posting with

      • Re:Legal action against Cambridge? (Score:5, Informative)

        by jabuzz (182671) on Tuesday July 04 2006, @12:44PM (#15656798) Homepage
        Wrong Cambridge, Cambridge Univeristy (fourth oldest in the world) is in the South East of England, and not in North America. Full marks you have displayed a typically parochial American outlook on the World.

        • This will make the Chinese government mandates antispoofing by all ISPs. Which actually will be quite a good thing. As a result at least one country in the world will mostly drop off the D.O.S. map. Good thing all around actually.

          Now an interesting Cambridge related question is how it relates to the Great Firewall of Britain, aka Clean Feed (TM) which the dictatorship of el presidente de partida Laborista Antonio Bliar has forced most ISPs to implement (in the name of the children and terrorism of course)

          • arrggghhh!! NO, do you know how long it took me to find an ISP that would actually support spoofed source packets, even though our use for them wasnt evil!!! Just because there is evil uses for a technology doesnt mean that there arent also positive uses!!!

            The Such and Such is evil lets block it mentality is not a good thing(TM)...

            I can understand why spoofed source packets are bad and the majority of the time they are being used for illicit purposes, but should we ban bit torrent because the majority of th
            • Several problems with it:

              The primary problem is that the list is not under direct public control of an independent and accountable body.

              From there on it can be used for blocking any content El Presidente Antonio Bliar can deem undesirable. Further to that, one of the functions of Clean Feed is a transparent redirect which will redirect your traffic to a site different from the one you are requesting.

              Considering the record of this government on telling the truth that is a very dangerous weapon to give to the

  • Mongolians? (Score:5, Funny)

    by veinard (469297) on Tuesday July 04 2006, @12:13PM (#15656683)
    Weird, I didn't know there were many mongolians at cambridge...

  • Stateless? (Score:3, Interesting)

    by Anonymous Coward on Tuesday July 04 2006, @12:13PM (#15656685)
    How exactly does a stateless IDS block connections for up to an hour? Are there other components to the firewall I'm not aware of, or does stateless mean something else these days?

    • Re:Stateless? (Score:5, Informative)

      by Just Some Guy (3352) <kirk+slashdot@strauser.com> on Tuesday July 04 2006, @12:18PM (#15656700) Homepage Journal
      How exactly does a stateless IDS block connections for up to an hour?

      Stateless != ruleless. For example, you could use OpenBSD's "pf" to create a stateless firewall that references an external rules file, then use a cron job to rewrite that rules file once an hour. That might be a pretty reasonable approach if you're filtering billions of packets per hour and can't afford to track state for each connection.

        • That comment is bullshit. A lookup in the state table is actually _way_ more efficient than going through the ruleset for each packet, moreso if the ruleset is larger.

          You misspelled "this".

          State tables aren't happy magic O(zero) constructs - they take resources just like rulesets do. Imagine the case where a firewall is checking a billion simultaneous connections against a ruleset with only one entry. Do you honestly content that it'd be easier to look for the existence of a state table entry than to

  • I can think of one useful application for this (Score:3, Interesting)

    by Ant P. (974313) on Tuesday July 04 2006, @12:19PM (#15656704) Homepage
    An "active" spamfilter that automatically shoots down chinese spammers. The IP gets blocked off for an hour and can't spam anyone at all outside china.

    Of course at the same time I can think of a million abusive applications for this...

  • Solution? (Score:5, Insightful)

    by QuantumFTL (197300) * <justin@wick.gmail@com> on Tuesday July 04 2006, @12:19PM (#15656705) Homepage
    I wonder what the chinese government would do if groups of individuals from around the world used techniques like this to DDoS the firewall. I highly doubt that they could get their population to accept them completely shutting off access to the outside world, and a stateful firewall would be considerably more expensive, assuming they wanted to keep their same (terrible) level of performance.

    What does slashdot think about this?

  • I wonder... (Score:4, Interesting)

    by mike260 (224212) on Tuesday July 04 2006, @12:21PM (#15656718)
    ...what would happen if I sent some packets from google.com to google.cn, containing words like 'democracy' and 'Falun Gong'.

    • Re:I wonder... (Score:4, Interesting)

      by Turn-X Alphonse (789240) on Tuesday July 04 2006, @12:36PM (#15656770) Journal
      Yes because a Chinese firewall is going to black English words right? They'll block the Chinese words obviously.

      • Re:I wonder... (Score:5, Interesting)

        by TubeSteak (669689) on Tuesday July 04 2006, @12:57PM (#15656842) Journal
        http://www.google.cn/search?q=Falun [google.cn]

        Falun Gong Is a Cult
        www.china-embassy.org

        Research Society of Falun Dafa and the Falun Gong organization under its control are held to be illegal
        english.people.com.cn

        Fifteen Falun Gong Cult followers attempted to sabotage cable TV network equipment
        app1.chinadaily.com.cn

        southcn:Falun Gong Cult OUTLAWED
        www.newsgd.com

        Here we should point out that the banning of "Falun Gong" by the Chinese government is also part of
        www.chinaembassycanada.org

        Falun Gong Practitioner Not Sorry for Killing Father, Wife
        news.xinhuanet.com

        Now compare all that to
        http://www.google.com/search?q=Falun [google.com]

        Now, if the Chinese Gov't is making Google filter based on English keywords, you think they're not going to do the same with their uber-firewall?

        Many Chinese schools teach english. It isn't like they only speak various Chinese dialects over there.
        • Interesting bit of facts you posted here. So Google does not simply censor keywords like "Falun". They block some web pages and let through others, those which say things convenient for the China government. Effectively, google.cn is an extension of the Chinese propaganda ministry. I wonder whether Google checks the content of the pages on its own, or does it get a list of the allowed pages from the Chinese? "Don't be evil" :))

  • That isn't technically a DDoS (Score:5, Informative)

    by Jeian (409916) on Tuesday July 04 2006, @12:31PM (#15656756)
    DDoS is using multiple computers to "flood" a target off the Internet. This would be a plain DoS attack using a software weakness to deny service.
    • A DDoS attack is an attack that is distributed across many machines colaborating to bring down a target machine. It does not necessarialy have to flood a target off the machine in the sense of a SYN attack. For that matter - as in the case of the SYN attack - it doesn't have to be from multiple identifiable sources; simply from many sources.

      RTFA. The attack can be either from a single machine, or it can be distributed. The source of the attack is unimportant. Either a single machine can generate the pa

  • Try the Saudi firewall (Score:5, Interesting)

    by Anonymous Coward on Tuesday July 04 2006, @12:40PM (#15656781)
    Chinese firewall is nothing - try getting through the Saudi firewall. As I understand it, the Chinese are at least a bit less modest about what is banned, so you should be able to at least get some legit porn sites through Chinese internet. However Saudi internet would block not just porn sites, but womens rights websites, womens magazines websites, even medical sites - anything that would display a photograph or illustration of a naked woman or man was stricly banned. Even it was just part of a human body, i.e. shoulders up.

  • Benefits of the wall (Score:3, Interesting)

    by debrain (29228) on Tuesday July 04 2006, @12:52PM (#15656825) Journal
    I think there are some good points to the existence of the firewall. While the firewall itself is a bad thing, no doubt, the fact that the Chinese have access to the internet at all is a huge step forward for them. We're talking about a country that was totalitarian for centuries, with virtually no interest in or comprehension of indivdiual human freedoms.

    It also speaks to the power of the internet's design. Here is a nation notorious for its control of information, and the techniques they use are easy to discover, and possible to circumvent. If China can't restrict the internet, then there's hope that other governments and maybe even multinational corporations won't be able to pull it off either.

    With luck, the firewall will become an irony of the past, as the importance of human dignity becomes apparant to the Chinese government.

  • National Security (Score:5, Insightful)

    by subl33t (739983) on Tuesday July 04 2006, @01:31PM (#15656961)
    Go ahead, mod me down.

    Couldn't the Chinese government view this as an act of terrorism? In the interest of national security the Chinese government will start an ambiguous "War on Terror" after the the US "War on Terror" and "War on Drugs" which are _also_ unwinnable and declared solely to keep the ruling party in power via fear.

    • The Terrorist Song
      by Usurper_ii
      (Sung to the tune of Python's The Lumber Jack Song)

      I'm a terrorist and I'm OK
      I read at night and I work all day.

      The Government:
      He's a terrorist and he's OK
      He reads at night and he works all day.

      I read a lot and I seek the truth
      I go to the lavatory.
      After OKC, I saw some things that didn't make sense to me.

      The Government:
      He doesn't believe our story about OKC,
      We monitor when he goes to the lavatory.
      On Wednesday night, he went to an unapproved web site.

      Chorus:
      He's a terrorist and he's OK
      He reads at night and he works all day.

      When, after 9-11 didn't all add up,
      I met with others on the net, to talk it up.

      The government:
      He didn't believe our story about 9-11.
      We followed him to unapproved web sites after hours.
      In our report, well say he had bomb-making materials under his sink.

      Chorus:
      He's a terrorist and he's OK
      He reads at night and he works all day.

      I don't think a plane hit the Pentagon.
      I think the World Trade Center buildings fell all wrong.
      I wish I could convince my dear ol' mom!!

      The government:
      He's a terrorist and we're going to make him pay?!
      We read his e-mail and didn't like what he had to say?!...

      Just me:
      I wish I'd been born, back when America was really free!!

      The Government:
      He's a terrorist and we're going to make him pay
      He reads the Constitution and knows his rights.
      He's just like McVeigh, Bin Laden, and al-Qaeda!!

      Chorus:
      He's a terrorist and he's OK
      He reads at night and he works all day.

       

  • Cyber Attacks, a good thing?? (Score:5, Insightful)

    by Theovon (109752) on Tuesday July 04 2006, @01:33PM (#15656966)
    Is it just me, or does it seem rather unkind to go about declaring, "Look at me! I just conducted a cyber-attack against China!" Hey, I'm no fan of China's government or censorship, and I am aware that China have tried to attack other countries' computers, but two wrongs don't make a right. Unless we're doing something defensive to ward off an attack from China, I see little point in taunting them and giving them reason to tighten security even further. It just doesn't seem right.

  • Last weeks news - original post here (Score:5, Informative)

    by erik_norgaard (692400) on Tuesday July 04 2006, @02:39PM (#15657186) Homepage
    It appears the link to the source is missing - I first read about it last week on Schneiers blog, linking ot the original blog post found here:

        http://www.lightbluetouchpaper.org/2006/06/27/igno ring-the-great-firewall-of-china/ [lightbluetouchpaper.org]

    And for all the details, the paper to be presented is here:

        http://www.cl.cam.ac.uk/~rnc1/ignoring.pdf [cam.ac.uk]

    I think the interesting thing is that by configuring our end to ignore the invalid resets from the Great Firewall of China we can aid the distribution of otherwise censored material.

    DDoS attacks against the GFC seems not to be that easy, as the article mentions the GFC is not one giant router at the backbone, but rather smaller machines closer to the end stations - the firewall is distributed accross an unknown number of gateways.

    • Re:Congratulations (Score:4, Insightful)

      by Trigun (685027) <evil@nosPAM.evilempire.ath.cx> on Tuesday July 04 2006, @12:12PM (#15656682)
      Better they do it from the outside then the Chinese government find the guys doing it from the inside.

    • Re:Congratulations (Score:5, Interesting)

      by TubeSteak (669689) on Tuesday July 04 2006, @12:47PM (#15656806) Journal
      Well done on writting a 'how-to' on pointers to make the firewall better.
      Actually, this flaw is inherent to the design of the great firewall.

      It's not something that is trivial to fix. Others can do a better job of explaining why, but for now, suffice it to say that it'd require a significant effort on the part of the Chinese Gov't.

      Maybe it can be fixed in The Great Firewall of China v2.0

    • Re:Congratulations; Same old tired argument. (Score:5, Interesting)

      by posterlogo (943853) on Tuesday July 04 2006, @01:11PM (#15656891)

      Well done on writting a 'how-to' on pointers to make the firewall better. Im sure people out there new these things, and used them to their advantage. Now all holes will be plugged and even more censorship will rein in China. You have now had your 15mins of fame.

      This is the same old tired argument we hear here on Slashdot over and over again. Expose the flaws and you either 1) alert the hackers on how to expose them or 2) Allow the admins to patch them. It's funny how depending on your political ideology, people will swing either way. How about a consistent opinion in favor of revealing flaws? Those who favor security by obscurity deserve neither.

        • There's a reason people never agree on security through obscurity. Hell you've generalized that people believing in it don't like public disclosure. I personally feel it can deter script kiddies as their scripts occasionally look for banners, etc. There are cases it can help. Not everyone is smart enough to use a program to determine OS type, or other fingerprinting strategies.

          I think these researchers just proved once again that nothing is uncrackable. The idea of security is similar to the titanic.

            • Re:Congratulations; Same old tired argument. (Score:4, Informative)

              by John Courtland (585609) on Tuesday July 04 2006, @04:52PM (#15657538)
              The banner can tell you program version information and sometimes the host OS, machine architecture and running modules. Apache's webserver banner is a good example. It can, if set up to, tell you the version of apache, the version of PHP, the host OS kernel revision, and what processor is hosting that OS. That's a lot of information that really isn't necessary. Usually it's displayed when a ErrorDocument handler returns a 404 itself.
    • It's information.

      They're academics.

      Their whole raison d'etre is to learns and share their learning. The information itself is ethically neutral. It can be used for good or for bad.

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