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Obscurity Is a Valid Security Layer

• hammock 10y ago
  This argument is a strawman. Does OP have a real example of someone arguing that obscurity as a layer on top of good security is a bad thing?
  • danpalmer 10y ago
    I don't think it's that bad, but if you believe that security through obscurity is not secure, and you are using it with something that is secure, then it is in practice adding nothing, and not worth it.
  • pjungwir 10y ago
    I hear people call moving the ssh port "security by obscurity" all the time. For instance: http://serverfault.com/questions/189282/why-change-default-ssh-port http://serverfault.com/questions/189282/why-change-default-s... http://serverfault.com/questions/316516/does-changing-default-port-number-actually-increase-security http://serverfault.com/questions/316516/does-changing-defaul...
  • raesene2 10y ago
    Yeah go look on security stackexchange and you'll see it quite a bit, people just cargo cult the idea of obscurity == bad and don't consider the points made in OP's article
• danpalmer 10y ago
  It seems here that the author has a different definition of security through obscurity to many who criticise it. The important aspect is whether the knowledge required to break the system is the system itself, or the key. AES is not security through obscurity because everyone can look up how it works, and it's only the key that we have to keep secret. Port knocking is the same (just with a weaker key). Moving your SSH to port 24 however is security through obscurity because if anyone knows the mechanics of how you use it, they can use it. This differentiation is subtle, and can be somewhat of a grey area sometimes, but I find it good at differentiating between the two most of the time.
  • kevincox 10y ago
    Couldn't you argue that the port SSH listens on is a 16 bit key? It's small and easy to brute force (among numerous other ways it is easy to discover) but I don't really see distinction you are trying to make.
    • eximius 10y ago
      At the information theoretic level, isn't everything? The only thing that makes this more like a 'key' is that there is a simple test for it. More complex configurations of obscurity are not really brute-forceable, just discoverable. That was less clear than I'd have like.
    • danpalmer 10y ago
      Yes, this is what I mean by it being a subtle and not always clear difference, but I think it's usually pretty easy to apply common sense to this.
  • theandrewbailey 10y ago
    > Moving your SSH to port 24 however is security through obscurity because if anyone knows the mechanics of how you use it, they can use it. An attacker still needs to authenticate against SSH on that non-standard port. The whole world could know about it, but the security of the system is not greatly impacted.
    • AstralStorm 10y ago
      Except said port is not tested all the time by helpful automated test systems developed by attackers.
      • PeterisP 10y ago
        If you're running a real service behind that port, then those "helpful automated test systems" aren't helping you since either they don't succeed and don't do anything, or they succeed and hurt you. If you're running a honeypot behind port 22, well, that works well with putting the real service on another port or behind port knocking.
• Confiks 10y ago
  It's good someone finally took the effort to write this up. When discussing some security by obscurity measure, other people almost invariably come up with the "security by obscurity is bad" slogan without having spent much thought on /why/ it is bad in that instance. Now this piece can be conveniently linked. Somewhat differently, sometimes security by obscurity is confused with using a proper key. For example, with most webservers you can pretty safely restrict access to a file by giving it a filename containing some key that cannot realistically be guessed. Barring other ways in which an attacker could find out about the presence of the file – which is quite easy to fuckup in some environments, and is why you shouldn't do this if you really want to be secure – someone without the key cannot access the file, and thus it shouldn't be called security by obscurity; the method is public, the key is not.
  • mikeash 10y ago
    What should be said is that security only through obscurity is bad. Security through obscurity is fine as long as you're not relying on it. At the worst, it doesn't hurt, just don't count on it to save your bacon.
    • dllthomas 10y ago
      > At the worst, it doesn't hurt At the worst, it imposes cost for little benefit.
      • sametmax 10y ago
        Obscurity almost always drive down script kiddies and generic bots away so the cost is amortized by the ressource you save and can focus on real threats.
        • AstralStorm 10y ago
          Or instead assume that your untested defences are working. Or in case of an obscure algorithm, assume it is good, because it had not been challenged.
• omginternets 10y ago
  I've often felt there was an interesting discussion to have about obscurity. It's interesting because although the infosec community has such a strong reaction to the phrase "security by obscurity", it has a very different reaction to the phrase "obfuscation". I'd like to propose a distinction between the two: - "security by obscurity" would refer to the non-declaration of configuration and parameters - "obfuscation" would refer to the deliberate fuzzing of statistical means by which such configuration and parameters can be discovered. The distinction is admittedly fuzzy, but the idea is that "security by obscurity" is trivially defeated by treating the target system as a statistical problem. If said system can be repeatedly probed, then useful information can be gleaned. With obfuscation, one is deliberately injecting noise into the signal that the attacker is trying to analyze. What do you all think? Is this a useful distinction? To be perfectly clear, I don't mean to imply that obfuscation is a sufficient security mechanism, but rather: 1. that obfuscation is more useful than plain-old obscurity 2. we should understand that infosec attacks are often statistical in nature Regarding point 2, I think this ends up shedding more light on what, exactly, is wrong with "security by obscurity" as it's often debated.
  • blakesterz 10y ago
    1. & 2. Totally agree. On point 2 I've recently come to the conclusion that I can't worry about every damn thing. I follow all the ITSec news pretty closely and there's just SO MUCH WRONG with everything (or at least it feels like it). Security researchers seem to love to freak out about everything (it's their job after all)_but I just don't have the time. If something is going to be a likely attack, easily done, remotely, today or next month, then it's something I need to worry about. If this is a theoretical attack based on something happening in the room next door I need to shrug it off, for now. There's many many things that fall in between those two extremes, and that's where I'm afraid I'm not sure what to worry about sometimes.
    • omginternets 10y ago
      I'd like to follow up on your post because you raise a lot of good points. In particular, we have a problem in infosec whereby "security" is implicitly equated to "security with cryptographic guarantees". I understand that "cryptographically secure" is the gold standard for infosec, but this misses a certain reality on the ground. Often times, your system doesn't need to be Fort Knox: it just needs to be a more difficult target than the other guy's system. I think this is where obfuscation comes in. With regards to well-known vulnerabilities, clearly cryptographic-grade solutions are required, but the best defense against zero-day attacks is to make your system hard to probe for odd behaviors. Why waste time doing statistical analyses on a system in the hopes of extracting a faint signal when another system literally responds to a port scan? I think the camouflage analogy in the article is a good one. Hardening your asset is necessary, but hiding it is even better. In my former military days, we were always told that "concealment is better than cover". It's hard to pull a flanking maneuver on a target you can't locate, but trivial to do so against a target you simply can't hit. I wouldn't go as far as to claim that the same is true in infosec, but it stands to reason that there's a place for concealment.
• fideloper 10y ago
  Can port knocking be used in the "real world"? In other words, would ~/.ssh/config or some other setting be able to automate the sequence? I'm picturing some current workflows I use if port knocking was enabled. In particular, unless there's a way to automate the knocking sequence, SSH'ing in via Ansible would be an issue and a SaaS we use to help with deployments would no longer work. (Altho I'd imagine making firewall exception rules (e.g. "allow this ip address in") for these services would be a way around that).
  • justinsaccount 10y ago
    I used to use something like this in ~/.ssh/config : Host Box Proxycommand ~/bin/do_knock %h %p Where do_knock was simply #!/bin/sh host=$1 port=$2 knock $host 1 2 3 4 5 nc $host $port && exit knock $host 1 2 3 4 5 sleep 1.5 nc $host $port Simply, but it worked well enough for a few years. On android I used to port knocking app that integrated with connectbot, so I had one tap access to the host.
  • jerf 10y ago
    Yes, it's off-the-shelf tech now. For example, see http://www.zeroflux.org/projects/knock http://www.zeroflux.org/projects/knock It's perhaps not as slick as you might hope, but it should be enough to shell script up some things.
• cdevs 10y ago
  Agreed considering I know someone who web scraped a entire dataset because they were selling 2500 sources for $15,000 a year and the API request were sequential ids 0-2500....so just curl 2500 request and call it a day because you didn't hash your ids
  • majewsky 10y ago
    By the way, hashing IDs would be a perfect example of security by obscurity if the hash was not salted. You just have to notice that you were given sha256("1234") instead of "1234".
• Tiquor 10y ago
  A valid security layer, but obscurity is not security.
• tptacek 10y ago
  I agree that obscurity has value in security designs --- security is in large part about imposing asymmetric costs on attackers. I do not believe that port knocking and single-packet authentication are good examples of this; both are sort of textbook examples of cosmetic security mechanisms that are made irrelevant by SSH public key authentication.
  • Tomte 10y ago
    I wouldn't focus on "security" when it comes to port-knocking. There are benefits beyond security: for example, less strange login attempts mean less clutter in your logs. If you're actually trying to investigate login attempts (don't!), it means less time wasted. The "security by obscurity" screaming people are usually thinking too narrowly, in my opinion.
    • tptacek 10y ago
      In discussions of port knocking and SPA among my security friends, it always comes down to this argument: cleaning up the logs. Why not just alter the way SSH logs? Perhaps it can just log once every couple of minutes, "yes, people are still probing this server".
      • justinsaccount 10y ago
        Here's a simple example: Running sshd on port 22, seeing repeated authentication failures in the logs. conclusion: business as usual for sitting on the internet. signal to noise ratio: almost 0. Running sshd on port $RANDOM, seeing ANY authentication failures in the logs. conclusion: someone is specifically targeting me or my network, I might want to pay some attention to this. signal to noise ratio: 1.
        • zeveb 10y ago
          Running on a random port isn't the same as using port knocking; if you're on a random port you'll get hit anyway (I think it falls under 'business as usual for sitting on the Internet'). Port knocking & single-packet authorisation, though, do provide some protection: if you get a failed login attempt via PK/SPA-protected SSH, then you know you're targeted (and also, your PK/SPA key is bad).
• diziet 10y ago
  The real problem with obscurity as a security layer is that it complicates day to day work that you'd be doing with that system. Each new person needs to be constantly trained and reminded about your specific system quicks and configuration outside the standard norm before they can do work using the system. That has a real cost, and it is a cost analysis question.
  • jlg23 10y ago
    That really depends on the use case. We too have sshd listening on a non-standard port and the overhead to tell people what to put into their .ssh/config is negligible. We use SPA only on very few select servers that less people need to access and those just get the shell script they need to run instead of typing "ssh $host". After about 2 years of running things this way: The time saved in checking system logs in a single week was much more than the time spent on "training" people in those 2 years.
• justinsaccount 10y ago
  Nice work. There are a lot of claims out there about this sort of thing, and not a lot of hard data. If you had used a port other than 24 you would have seen 0 attempts. Port 24 is still scanned fairly frequently, something like 22X where X !=2 is almost never scanned. If you block port 22 and use iptables to redirect a random high port to port 22, you'll never see any connection attempts - unless someone is really targeting you. I did a bunch of reporting/math against our data a few months ago the last times this came up on reddit. I found a few interesting things and tried to counter some bogus claims. First bogus claim: Shodan scans everything, so you can't hide. I checked for the entire month of feburary for a large address space, shodan scanned these ports: 0 3 7 11 13 15 17 19 21 22 23 25 26 37 49 53 67 69 70 79 80 81 82 83 84 88 102 110 111 119 123 129 137 143 161 175 179 195 311 389 443 444 445 465 500 502 503 504 515 520 523 554 587 623 626 631 666 771 789 873 902 992 993 995 1010 1023 1025 1099 1177 1200 1234 1311 1434 1471 1604 1723 1777 1883 1900 1911 1962 1991 2000 2067 2082 2083 2086 2087 2123 2152 2181 2222 2323 2332 2375 2376 2404 2455 2480 2628 3000 3128 3306 3386 3388 3389 3460 3541 3542 3689 3749 3780 3784 3790 4000 4022 4040 4063 4064 4369 4443 4444 4500 4567 4848 4911 4949 5000 5001 5006 5007 5008 5009 5060 5094 5222 5269 5353 5357 5432 5555 5560 5577 5632 5672 5800 5900 5901 5984 5985 5986 6000 6379 6664 6666 6667 6881 6969 7071 7218 7474 7547 7548 7657 7777 7779 8000 8010 8060 8069 8080 8081 8086 8087 8089 8090 8098 8099 8112 8139 8140 8181 8333 8334 8443 8554 8649 8834 8880 8888 8889 9000 9001 9002 9051 9080 9100 9151 9160 9191 9200 9443 9595 9600 9943 9944 9981 9999 10000 10001 10243 11211 12345 13579 14147 16010 17000 18245 20000 20547 21025 21379 23023 23424 25105 25565 27015 27017 28017 30718 32400 32764 37777 44818 47808 49152 49153 50070 50100 51106 55553 55554 62078 64738 2nd bogus claim: "A single host on a decent connection will be able to scan all ports on a /16 in less then an hour. I see scans like this all the time." It is the same amount of work to scan every ipv4 address on port 22 as it is to scan every port on a /16. Every port on a /16 is 2^32 (65536 ports on 65536 hosts) or 4294967296 ports. Saying it can be done on a "decent" connection in less than an hour, at 4294967296 ports in 3600 seconds works out to 1,193,046 packets/second. Line rate gigE maxes out at 1,488,095 pps. You would need to saturate a full gigabit for an hour to fully scan a /16 - and a full gigabit at whatever site you are scanning. with 0% packet loss. 3rd bogus claim: (re port knocking) Faster internet speeds means more scanning power which means that it gets easier to find your hidden service If I am using a non cryptographic port knocking daemon with a 4 port knocking sequence, that has 65536^4 combinations. One should probably figure out what the length of the shorter De Bruijn sequence is for guessing 4 port sequences, which I believe just works out to around "only" 65536^4 packets instead of 4 times that. Also assuming the correct sequence would be found halfway through, that would mean 9223372036854775808 packets required to be sent. At line rate gigE, that would take 6198107000463 seconds, or 196,540 years. Only 19,654 years at line rate 10gig though!
• goodside 10y ago
  This argument seems disingenuous. It's no great insight that port knocking reduces unauthorized login attempts. What's disputed is whether it's better to have a system that's rarely challenged vs. a system that's regularly challenged and still holds. The argument against is that adding layers of bad security makes it easier for problems in the "real" security to go undetected or ignored since the obscurity layer works too well.
  • dogma1138 10y ago
    I agree people confuse obscurity with "operational security". Reducing your footprint, and keeping information disclosure to a minimum isn't obscurity. On the more specific examples while port knocking is an acceptable security mechanism (so is geoblocking, and even whitelisting specific IP's only) it's again not obscurity, putting connections on random ports is and it can also be a very bad practice because obscurity often works both ways. In a large organization even one with great documentation and knowledge management things will fall between the cracks, if we take their example to the then while the attacker might be slightly less likely to identify a non standard SSH port (because for some reason they assume that port scanning is expensive) it can also mean that your own security teams and tools can miss them just as easily. When heartbleed came out for example people run it on the common SSL ports internally, pretty much all of it was patched rather quickly but from time to time you still find an instance of it and usually it's because some developer somewhere decided port 23216 is a good port for SSL. The attackers are considerably more likely to perform allot of information gathering on their target, more so than internal teams, internal security tools often limit their tests to standard and specified ports because when the security team has a 4 hour window each month to turn their vuln scan a full TCP port scan is probably out of the question on a network with few 1000's of IP's and larger. By adding unnecessary obscurity to your system you are effectively only increasing the likelihood of you missing something while the attacker is just as likely to find it as anything else.
• geggam 10y ago
  I think port knocking is like anti virus ... it makes you feel safe so you run obsolete software and get p0wned
• Grollicus 10y ago
  Why is moving the SSH port Security by Obscurity? Its log cleaning by avoiding annoying portscans, nothing else.. There is NO Security gained by moving the port. If you think random portscans are a security risk to your SSH server you should seriously reconsider your SSH configuration.
  • zippergz 10y ago
    So you don't think you're less likely to be compromised by a 0day OpenSSH worm if your sshd is running on a non-standard port? Why?
    • xyience 10y ago
      You might not get compromised in the first wave of IP scanners that try the 0day on port 22, port 2222, and maybe a few other common alternatives. This first wave will pass in about 5 minutes. Subsequent waves will just try every port. This isn't costly, they have an army of compromised machines from the first wave.
      • zippergz 10y ago
        Can you give me an example of a real-world worm that has scanned every port on every system on the internet? I haven't seen one, but if it exists, I'd be curious to see it. I'm speaking based on the actual exploits I've seen in the wild over the past 15-20 years, not what is hypothetically possible.
        • xyience 10y ago
          Not every port, but maybe you remember this: http://arstechnica.com/security/2013/03/guerilla-researcher-created-epic-botnet-to-scan-billions-of-ip-addresses/ http://arstechnica.com/security/2013/03/guerilla-researcher-... The article also details an earlier cataloging where a researcher probed 18 ports 3-4 times a day over the ipv4 address space. Tools like ZMap or MASSCAN make it easy for anyone to scan as many ports as they can, but I haven't heard of any worm that systematically tried all 65535 ports of all addresses. Though I would bet a lot of money that an OpenSSH 0day that bypassed all authentication would result in several such worms from multiple actors who already control hundreds of thousands of devices.
• jfindley 10y ago
  Moving the SSH port is a bad idea. The article falls into a number of common pitfalls here. A connection to your SSH server does not usefully equate to someone "trying to hack" your server. If I had $1 for every time I've heard this complaint, I'd be very rich, but it's total rubbish. Stop worrying about it. The mass scanners that fill your logs with brute force attempts on port 22 are looking for trivially obvious username/password combinations. If there is any chance they could actually get in with this approach, you've screwed up so badly that moving the port will not save you. If you're using key-based authentication, no amount of scanning is ever going to compromise your server, unless the attacker learns your key. The reason moving your port is pointless is that against an attacker sophisticated enough to have any chance of compromising your SSH server, no amount of hiding the port is going to do more than delay them a few minutes. Compromising SSHv2 is hard. You need either a key compromise (difficult to achieve, likely some sort of APT malware against your laptop), or a zero-day sshd vulnerability. Against someone motivated and able to do that, your "clever trick" of moving sshd to port 24 is totally useless. It's a bad idea to propose, too, as it will require users to either update SELinux rules to allow sshd to bind to a different port, or disable SELinux entirely. And as many of the ports <= 1024 are used for other things, users will tend to do things like bind to ports > 1024, such as 2222. As any system user can bind to ports > 1024, you're actually reducing security, and opening up a potential priv escalation vector (user with unpriv shell access causes sshd to crash via XYZ, starts their own malicious daemon on 2222, steals your credentials, etc). There are cases where obscurity helps. Reducing the amount of information an attacker has about the environment they are attacking is often a very valid defence, and is something any security audit should consider. Moving the sshd port is not one of these cases. In short, make sure you're using key-based authentication (ed25519 is preferred IMO, but happy for others to debate this). Make sure password authentication is disabled. Make sure direct root ssh is disabled, and passwordless sudo is disabled. Leave the port sshd listens on well alone - it's just fine where it is.
  • draw_down 10y ago
    It's not meant as a defense against a sophisticated attacker.
    • 10y ago
• domador 10y ago
  As long as the goal of obscurity isn't to hide a weak or poor underlying security system, there might be some benefit to obscurity as an ADDITIONAL layer, as claimed.
• TheGuyWhoCodes 10y ago
  Moving the SSH port if you are already using port knocking with SPA is kinda useless, nevertheless I agree with the premise of the article, I really like the M1 analogy.
• zeveb 10y ago
  > Remember, the NSA most likely has great algorithms, but they still don’t publish them. Not quite: https://en.wikipedia.org/wiki/NSA_Suite_B_Cryptography https://en.wikipedia.org/wiki/NSA_Suite_B_Cryptography They don't publish all of them, I'm sure, but they did publish Suite B.
  • nickpsecurity 10y ago
    The ones relevant to the quote are here: https://en.wikipedia.org/wiki/NSA_Suite_A_Cryptography https://en.wikipedia.org/wiki/NSA_Suite_A_Cryptography They along with the Type 1 development and certification process are used for stuff they trust the most. Suite B algorithms can be used with Type 1 implementation for very, critical stuff as well. The Type 1 is the key for assurance more than the algorithms themselves. It ensures the protocols and algorithms are rigorously implemented. Includes considerations on RNG's, common coding flaws, covert channel analysis, and TEMPEST shielding. Only smartcard sector comes anywhere near assurance activities that go into Suite A or Type 1 products in terms of crypto.
• jijojv 10y ago
  Agree that changing SSH ports on public facing servers is a great use case for obscurity but I hate when "security minded" people use that inside private data centers which just makes scp/rsync etc. very annoying without adding the same security value.
• floatboth 10y ago
  I'm not even sure if I agree or not. I get the point, but I kinda want random attack bots to try logging into my sshd with common passwords. It's like a free security scan!
  • AstralStorm 10y ago
    Use a separated or virtualized clone in a honeypot though. It is not good to risk your main servers and security for this.
    • ryanlol 10y ago
      This shouldn't qualify as a security risk, if it does there's something very wrong with your setup.
      • AstralStorm 10y ago
        Of course. But in case something is seriously wrong, you probably want the compromise to happen on an isolated system and not main production one or one containing critical data. Separation of concerns and compartmentalization are both very good things from security point of view.
• throw7 10y ago
  Obscurity is "bad" security because when you're told "how it works" it's usually very weak and easily defeated. Pairing up obscurity with "good" security should be more of a "do the benefits outweigh the costs?" type of question and only each site can answer this question. I sincerely believe no one, crosses finger, argues that security by obscurity alone is good security. -.-
• apaprocki 10y ago
  I know some people who try to extend this thinking to software libraries. Ask yourself if the world would be better served if OpenSSL was closed-source and therefore could not be analyzed for bugs so easily by attackers. It's a slippery slope... but I see regular arguments why a particular piece of software is "technically" more secure by some level of obscurity (restricting access).
• nickpsecurity 10y ago
  Obfuscation has been one of my strongest measures for security for a long time. Cold War espionage writing taught me it's absolutely critical to defeating nation-state opponents given they'll always outsmart your specific, known techniques. What obfuscation does, if used effectively, is require the attacker to already have succeeded in some attack to even launch an attack. Defeating that paradox forces them to attack you in many ways, increasing work and exposure risk. The more obfuscation you have built in, the more that goes up. Very important moves to keep them effective are to ensure the obfuscation is invisible from users' or network perspective, make sure obfuscation itself doesn't negate key properties of security controls, make darned sure there are security controls rather than only obfuscation, only a few individual people knowing the obfuscations, and air gapped (or guarded) machines controlling them. Here are some obfuscations I've used in practice with success, including against strong attackers, per monitoring results, third party tests, and occasional feedback from sysadmins that apply them or independently invented them: 1. Use non-x86 and non-ARM processor combined with strong Linux or BSD configuration that also advertises as x86 box. Leave no visible evidence you're buying non-x86 boxes. This can work for servers. Some did it with PPC Mac's after they got discontinued. This one trick has stopped so many code execution attempts for so long it's crazy. I really thought a clever shortcut would appear by now outside browser Javascript, memory leaks, or something. An expansion on it with FPGA's is randomized instruction sets with logs & fail-safe for significant, repeated failures. 2. Non-standard ports, names, whatever for about everything. Works best if you're not relying on commercial boxes that might assume specific ports and such. So, be careful there. This one, though, just keeps out riff raff. Combine it with strong HIDS and NIDS in case smarter attackers slip up. Don't rely on it for them, though. 3. Covert, port-knocking schemes. An example of a design I think I modified and deployed was SILENTKNOCK. It gives no evidence a port-knocking scheme is in use unless they have clear picture of network activity. Even still, they can't be sure how your traffic was authorized by looking at the packets. Modifications to that scheme that don't negate security properties and/or use of safety-enhanced languages/compilers can improve its effectiveness. My deployment strategy for this and guards was a box in front of the server that did it transparently. Lets you protect Windows services prone to 0-days. Think it stopped an SSH attack or something on Linux once. Can't recall. Very flexible. Can be improved if combined with IP-level tunneling protocol machine-to-machine in intranet. Which can also be obfuscated. 4. Use of unpopular, but well-coded, software for key servers or apps. I especially did this for mail, DNS, web servers, and so on. Black hat economics means they usually focus on what brings them the most hacks for least time investment. This obfuscation counters their economic incentive by making them invest in attacking a niche market with almost no uptake. Works on desktops, too, where I recommended alternative Office suits, PDF readers, browsers, and so on that had at least same quality but not likely same 0-days as what was getting hit. 5. Security via Diversity. This builds on 4 where you combine economics and technology to force black hats to turn a general, one-size-fits-all hack into a targeted attack specifically for you. You might choose among safe libraries, languages, protocols, whatever without advertising their use in the critical app or service. Additionally, there's work in CompSci on compilers that automatically transform your code into equivalent, but slightly different, code with different probabilities of exploits due to different internal structure. That's not mature, yet, imho. You could say all the randomization schemes in things like OpenBSD and grsecurity fit into this too. Those are more mature & field-tested. If Googling, the key words for CompSci research here are "moving target," "security," "diversity," and "obfuscation" in various combinations. 6. My old, polymorphic crypto uses obfuscation. The strongest version combined three AES candidates in counter mode in layers. The candidates, their order, the counters, and of course the keys/nonces were randomized with exception being same one couldn't be used twice. That came from only criticism I got with evidence: DES meet in middle. FPGA's got good at accelerating specific algorithms. So, I modified it to allow weaker ciphers like IDEA or Blowfish in middle layer but no less than one AES candidate in evaluated configuration and implementation preferrably on outer layer. Prefferably two AES + 1 non-AES for computational complexity. All kinds of crypto people griped about this but never posted a single attack against such a scheme. Whereas, I provably stop one-size-fits-all attacks on crypto by layering several randomly with at least one strong one. Later, I saw TripleSec do a tiny subset of it with some praise. Also convinced Markus Ottella of Tinfoil Chat to create a non-OTP variant using a polycipher. He incorporated that plus our covert-channel mitigations to prevent traffic analysis. Fixed-size, fixed-transmission is obfuscation that does that I learned from high-security, military stuff. 7. Last one, inspired by recent research, is to use any SW or HW improvements from academia that have been robustly coded and evaluated. These usually make your system immune to common attacks [2], mitigate unauthorized information flows [3], create minimal TCB's [4] [5], use crypto to protect key ops [6], or obfuscate the crap out of everything [7]. I mainly recommend 1-6, though. ;) Then, don't advertise which ones you use. Also, I encourage FOSS developers to build on any that have been open-sourced to get them into better shape and quality than academics leave them. Academics tend to jump from project to project. They deserve the effort of making something production-quality if they designed a practical approach and kindly FOSS'd the demo for us. [1] http://www-users.cs.umn.edu/~hopper/silentknock_esorics.pdf http://www-users.cs.umn.edu/~hopper/silentknock_esorics.pdf [2] https://www.cis.upenn.edu/acg/softbound/ https://www.cis.upenn.edu/acg/softbound/ [3] https://www.cs.cornell.edu/projects/fabric/ https://www.cs.cornell.edu/projects/fabric/ Note: See related project in bottom-right for other good tech this builds on or was inspired by. [4] http://genode.org/ http://genode.org/ [5] https://robigalia.org/ https://robigalia.org/ [6] https://theses.lib.vt.edu/theses/available/etd-10112006-204811/unrestricted/edmison_joshua_dissertation.pdf https://theses.lib.vt.edu/theses/available/etd-10112006-2048... [7] http://www.ics.forth.gr/_publications/papadog-asist-ccs.pdf http://www.ics.forth.gr/_publications/papadog-asist-ccs.pdf
• Daviey 10y ago
  Security BY Obscurity is always bad. This article doesn't address this, but rather as an additional tool. ie, I wouldn't use telnet to control all of my servers and then think i am being secure because the IP addresses are not put in a server-list.txt on each server. However, using a secure protocol and not providing a network map on each server does provide a level of obscurity.
• marcosdumay 10y ago
  Well, yes, technically any amount of obscurity you add to your service increases your overall security. So let's go. You make a 256 bit level key. That's 256 bits of security there. For each binary thing that must be guessed together with the key (let's call those multiplicative), you gain an extra bit there. So, if you could somehow (what you can't) not disclose your encryption algorithm, you'd gain some easy 3 extra bits of security there. Now, if you have a secret that can be verified independently from your other secrets (let's call those additive), you'll gain one extra bit of security for every secret that has your overall security level. That is, if you add a 256 bit secure port knocking step (16 knocks on completely random pots) to your 256 bit secure key, you'll get 257 bits of security overall. If you add a 16 bit non-standard port, you'll get some fraction of a bit, starting with some dozens of zeros after the comma. Thus, since security is all about trade-off, think very hard about the costs of any additive measure you want to create.
  • stestagg 10y ago
    I think this reasoning is missing something. The maths assumes that the security of your system is entirely defined by the complexity of your key. Obscurity gives you the option of hiding the /lock/, which is different.
    • deleted 10y ago
      [deleted]
    • marcosdumay 10y ago
      I think you should read my comment again. Anyway, hiding your lock is additive (spreading fake locks would be multiplicative). How many bits of entropy does your lock obscurity have again? What does it cost?
  • contravariant 10y ago
    I think you're on to something, it makes sense to define the 'key' to represents everything that is secret, making "security through obscurity" contradictory. That said, the way you treated the additional information is somewhat disingenuous. It disregards that even though there might be 2^16 options they're not equally likely, assigning the same amount of information to each doesn't really represent the situation well. An alternative method would be to measure the information using the Kullback-Leibler divergence, which represents the information disadvantage a distribution has to the actual distribution. In this case the attacker would believe the key to have a probability distribution, whereas the target knows the key exactly. In which case the expression for the KL-divergence is simply -log(p), where p is the probability the attacker assigns to the actual key. When there are N options, all equally likely this agrees with the usual notion of entropy. However if the attacker assigns a very low probability to some option (i.e. using a different port) then the effective key complexity could become quite high. If the attacker considers the key impossible (i.e. p=0) the the effective key complexity would even be infinite. In the article they gave an example of 18,000 connections vs 5, which would effectively give you 12 extra bits of security (with very little effort). I'm not sure entirely sure what the optimal tactic would be for searching a non-uniformly distributed key space, but from it's definition the KL-divergence does measure the amount of information to determine the 'actual' distribution. I strongly suspect that there is no way to get around this (on average).
• jdblair 10y ago
  I just checked my home ssh endpoint, which runs on a non-standard port on my firewall. I was surprised to discover there have been zero scan attempts. I am using comcast xfinity for my home internet access.
• burnstek 10y ago
  Great sentiments. I don't see security being discussed nearly enough in terms of risk and ROI. I usually see it discussed only in absolute terms, i.e. unless a solution fits the "CIA" model to a T, then it's unacceptable. I think that we should layer the CIA triad on top of the Time-Cost-Quality triad when implementing application security.
• seanwilson 10y ago
  Heavily agree with this. I read people stating "security by obscurity is bad" without really thinking about it all the time. For example, I think changing the SSH server port and WordPress login pages are a good idea because 1) if a hacker cannot find the login location in the first place, your chance of getting hacked must decrease and 2) the number of intrusion attempts being logged will be significantly less so you can more usefully survey these for targeted attacks. Of course, relying only on obscurity is a terrible idea but you should have several layers of obstacles so if one fails the security violation will get caught at the next layer. Avoiding security through obscurity completely is more something you should do when designing a secure protocol or algorithm.
  • TickleSteve 10y ago
    There is the concept of "Defense in depth", used by the military for many years... This acknowledges that each layer is bound to have holes, therefore the best you can hope for is to delay the inevitable breach. Therefore, any additional layer you can add to the security increases the time taken and hence gives you a better chance at rebutting the attack.
• seanwilson 10y ago
  For people saying security through obscurity should always be avoided, if you have a web service that is only required internally on the private network, would you make it public?
  • Kliment 10y ago
    There's a difference between public, as in publicly accessible, and public as in externally visible. In your situation, you should not make it externally accessible, so it doesn't make a difference if it's externally visible or not (though there is no reason to make it externally visible).
    • seanwilson 10y ago
      Is making it externally invisible not a form of obscurity though? If so, why is this not frowned upon as well?
• mrdrozdov 10y ago
  Passive scans that hit your port 22 can hardly be called a security issue, and changing your port number definitely does not add any sort of security. This is a confusing concept, since changing your port number might decrease the probability your server gets taken advantage of (temporarily). It's a trivial fix for attackers everywhere to scan multiple ports instead of one at marginal cost.
• Havoc 10y ago
  Its valid in a way, but the second you count it as one of you security layers you risk relying on it...and thats where it becomes dangerous. Should really be more of a bonus layer so to speak.
• eslaught 10y ago
  There is a certain danger with obscurity in it can obscure to your own vulnerabilities. I believe this is most well-known with crypto, where essentially any proprietary crypto algorithm should be assumed to be broken (because crypto is just that hard), but it applies to all forms of security. To put it another way: public (and popular) security measures have the benefit of having been validated by many eyes. When you choose proprietary security instead (which obsurity requires by definition, otherwise the technique would be known), you're betting that your own security team can do better. Is that a bet you can sometimes win? Perhaps, but I personally wouldn't want to bet too hard.
• EGreg 10y ago
  It is only useful if you don't publish open source software.a new, underfunded open source project is not the best place to find top-notch security. All the code is published so there is no obscurity, either. It takes a long time for security to be worked out, and in the meantime, systems can be compromised by dedicated hackers.
• BWStearns 10y ago
  The other thing to consider is that obscurity makes threat detection easier. If your sshd_config is set up for some random port and you get 18K attempts, then it's pretty clear that someone is interested in your server. If you're running it on port 22, then a slew of login attempts could be difficult to disambiguate from regular portscanning weather.
• Illniyar 10y ago
  The question isn't whether Obscurity provides security at all, but rather if the tradeoff you make with ease of use and maintenance is worth it. From my experience obscurity is usually trivial for a determined attacker to overcome, and if it's not a determined attacker your normal security layer will probably be insurmountable to an attacker of opportunity. For the small time (let's say an hour) that it'll add to a determined attacker's time you force your users to use an extra key just to detect the ssh port your using (the example he used in the article).
  • danielrm26 10y ago
    The point is to apply all your real security and then add obscurity afterwards to lower your risk even further. Wear the armor, then engage your cloaking device. Don't substitute the cloaking device for the armor, but also don't dismiss the value of not being targeted.
• lmm 10y ago
  > Let’s say that there’s a new zero day out for OpenSSH that’s owning boxes with impunity. Is anyone willing to argue that someone unleashing such an attack would be equally likely to launch it against non-standard port vs. port 22? If not, then your risk goes down by not being there, it’s that simple. You need to compare equal-cost approaches to security. For the amount of effort it takes to use a non-standard port, you could use a real security measure like single-use passwords instead - which would increase your security more? And you need to measure what your outcomes look like. If there's a new zero-day, do you really think those 5 attacks on the non-standard port won't use it? Do you think a targeted attack wouldn't use it? The result of getting caught in an ssh-scan of the whole internet is relatively benign - your server gets used to send some spam, you wipe it and rebuild. That's not the existential threat that security measures are about preventing.
• jrochkind1 10y ago
  I mean, I guess a password can be considered "security by obscurity", in the sense that it relies on keeping your password secret, the lack of knowledge about your password. So, sure, obscurity is a valid security layer. The problem is when people start thinking that port knocking is something different than a needlessly (emphasis on needlessly) complex method of implementing a very weak system-wide password.
• RawInfoSec 10y ago
  There's a number of things I disagree with in the article, but it does have a few good points. Here's what I disagree with and why: - Portknocking. I've found from experience that it's far better to allow SSH access (for example) from only known IP addresses. Portknocking is far too easy to beat and really doesn't impede much. - Non-standard ports. Sure if you're only interested in blocking bulk network scanners that limit themselves to known ports. Any manual scan or a solid in-depth scan is going to map every one of the lower 1024 ports, and possibly the rest depending on how interesting the target is. - The Tank camouflage example. It all sounds fine and dandy until a maintenance crew roam the desert for 10 days looking for a tank they can no longer see. Same with security and IT... obscurity leads to lots of wasted time when newer techs try to diagnose things that aren't as they seem, and are undocumented. Not only that, but the since the enemy know that the new armour requires a special ammunition to beat, they will just throw new ammo at everything that moves in case it is a tank. i.e. you're going to scan for hidden SSID's, your going to nmap every port, etc etc. Takes more time, but you still get in. - If there's a 0-day SSH vector, it's getting owned no matter which port it's on unless your security team are on top of patching. What if the new-hire that's told to go patch all the SSH servers accidentally misses the undocumented one that's running on port 24? It also doesn't matter if there's 10x more hits on port 22 than 24. All it takes is 1. It's that simple. I just don't think obscurity belongs in an environment where clarity matters so much.
  • lazyant 10y ago
    > Portknocking is far too easy to beat and really doesn't impede much. If you have to guess a random 3 port sequence in a 65k port space, how long will it take you to break? at 1 try of 3 ports per second I get almost 9 million years for exhaustive search.
    • RawInfoSec 10y ago
      Why guess when you can just sniff the network for the sequence? Port knocking requires the network that you're using to knock is in fact as secure and trusted as the one you're knocking. So there's really no point as you could easily just limit SSH access to that network and save yourself all the bother and risk.
• dlitz 10y ago
  It's still pretty expensive for very little added security benefit, which the added complexity might negate. How many bits of security does this add? 5 or 6? Maybe 32? People deploy ad hoc obscurity hacks like port-knocking because we have doubts our standard access-control infrastructure (e.g. libssl, SSH). It would be less wasteful to take the resources being spent on these hacks, and pool them together into projects that would boost our confidence in the infrastructure, instead. I can think of lots of security infrastructure projects that could probably use more resources: - The various libssl projects could probably use more resources. - There is at least one team working on formal proofs of implementation correctness for libssl. - Sandstorm.io is developing ways to move web access control (including CSRF protection) to an intermediate layer, rather than relying on individual web applications to get it right. - U2F is trying to bring cheap hardware tokens to web users, but it needs better support across the web. - Let's Encrypt/ACME is working on making it feasible to deprecate plaintext HTTP. There's still a lot of distro integration work to be done. - There's an IETF working group working on moving transport security into TCP itself (tcpinc). If it's done well (i.e. gets enough eyeballs), this could replace "libssl version hell" with straightforward socket file descriptors. - Most developers have no idea how to develop formal proofs of implementation correctness alongside their code. Educational materials would be great, here! - There are many, many legacy systems running still known-insecure software/protocols that need to be upgraded or worked around.
• gravypod 10y ago
  I think this is something very unsafe to preach to people. I'm not sure if this is a joke, or if this person and other comment authors are serious. The idea of Security-by-Obscurity is flawed inherently. Let me first start by defining security: "the state of being free from danger or threat." Now this is definitely not the best definition, it's just the one that came up when I googled the word and so this will work for now. The only way for security by obscurity to work, is for you to be able to design a system that is impossible to figure out or comprehend. Let's assume that one was able to design a system that is incomprehensible to anyone. Let's initially ignore the fact that if the system is not understandable to the user, it couldn't have been invented in the first place. I'll pose these questions: - If the system is so obscure to foreign users, how will it be maintained - If someone who knows the secrets of how this system is fired, what happens if they sell of their knowledge? - What would happen if there turns out to be a bug in this massive amorphous blob of crap that no one understands? How do you start debugging it without invalidating it's "security" I'll never use security-by-obscurity as a model. This is mainly due to one of my core beliefs: there are much smarter people out in the world then you. If you think "this is un-guessable" or "this is unbreakable" when slapping a bitshift on a stream of data and calling it "encryption" you need to understand that there are people smart enough in this world that can smell that from a mile away. I've worked with some of these people, and before then I may have said "yea security by obscurity" is fine; but having worked along side people who are FAR more intelligent then I am. Anything I can think of to circumvent their actions can be trivially figured out by someone out there who is smarter then I am.
• grymoire1 10y ago
  The phrase I use is "Security through obscurity provides temporary security which degrades over time"