The Center for Education and Research in Information Assurance and Security (CERIAS)
The Center for Education and Research inInformation Assurance and Security (CERIAS)
[tags]diversity, complexity, monocultures[/tags]
In my last post, I wrote about the problems brought about by complexity. Clearly, one should not take the mantra of “simplification” too far, and end up with a situation where everything is uniform, simple, and (perhaps) inefficient. In particular, simplification shouldn’t be taken to the point where diversity is sacrificed for simple uniformity.
Nature penalizes monocultures in biological systems. Monocultures are devastated by disease and predators because they have insufficient diversity to resist. The irish potato famine, the emerald ash borer, and the decimation of the Aztecs by smallpox are all examples of what happens when diversity is not present. Nature naturally promotes diversity to ensure a robust population.
We all practice diversity in our everyday lives. Diversity of motor vehicles, for instance supports fitness for purpose—a Camero, is not useful for hauling dozens of large boxes of materials. For that, we use a truck. However, for one person to get from point A to point B in an economical fashion, a truck is not the best choice. It might be cheaper and require less training to use the same vehicle for everything, but there are advantages to diversity. Or tableware—we have (perhaps) too many forks and spoon types in a formal placesetting, but try eating soup with a fork and you discover that some differentiation is useful!
In computing, competition has resulted in advances in hardware and software design. Choice among products has kept different approaches moving forward. Competition for research awards from DARPA and NSF has encouraged deeper thought and more focused proposals (and resultant development). Diversity in operating systems and programming languages brought many advancements in the era 1950-2000. However, expenses and attempts to cut staff have led to widespread homogenization of OS, applications, and languages over approximately the last decade.
Despite the many clear benefits of promoting diversity, too many organizations have adopted practices that prevent diversity of software and computing platforms. For example, the OMB/DoD Common Desktop initiative is one example where the government is steering personnel towards a monoculture that is more maintainable day-to-day, but which is probably more vulnerable to zero-day attacks and malware.
Disadvantages of homogeneity:
Advantages of homogeneity:
Disadvantages of heterogeneity:
Advantages of heterogeneity:
Reviewing the above lists makes clear that entities concerned with self-continuation and operation will promote diversity, despite some extra expense and effort. The potential disadvantages of diversity are all things that can be countered with planning or budget. The downsides of monocultures, however, cannot be so easily addressed.
Dan Geer wrote an interesting article for Queue Magazine about diversity, recently. It is worth a read.
The simplified conclusion: diversity is good to have.
[tags]complexity,security,virtualization,microkernels[/tags]
One of the key properties that works against strong security is complexity. Complexity poses problems in a number of ways. The more complexity in an operating system, for instance, the more difficult it is for those writing and maintaining it to understand how it will behave under extreme circumstances. Complexity makes it difficult to understand what is needed, and thus to write fault-free code. Complex systems are more difficult to test and prove properties about. Complex systems are more difficult to properly patch when faults are found, usually because of the difficulty in ensuring that there are no side-effects. Complex systems can have backdoors and trojan code implanted that is more difficult to find because of complexity. Complex operations tend to have more failure modes. Complex operations may also have longer windows where race conditions can be exploited. Complex code also tends to be bigger than simple code, and that means more opportunity for accidents, omissions and manifestation of code errors.
It is simple that complexity creates problems.
Saltzer and Schroeder identified it in their 1972 paper in CACM. They referred to “economy of mechanism” as their #1 design principle for secure systems.
Some of the biggest problems we have now in security (and arguably, computing) are caused by “feature creep” as we continue to expand systems to add new features. Yes, those new features add new capabilities, but often the additions are foisted off on everyone whether they want them or not. Thus, everyone has to suffer the consequences of the next exapnded release of Linux, Windows (Vista), Oracle, and so on. Many of the new features are there as legitimate improvements for everyone, but some are of interest to only a minority of users, and others are simply there because the designers thought they might be nifty. And besides, why would someone upgrade unless there were lots of new features?
Of course, this has secondary effects on complexity in addition to the obvious complexity of a system with new features. One example has to do with backwards compatibility. Because customers are unlikely to upgrade to the new, improved product if it means they have to throw out their old applications and data, the software producers need to provide extra code for compatibility with legacy systems. This is not often straight-forward—it adds new complexity.
Another form of complexity has to do with hardware changes. The increase in software complexity has been one motivating factor for hardware designers, and has been for quite some time. Back in the 1960s when systems began to support time sharing, virtual memory became a necessity, and the hardware mechanisms for page and segment tables needed to be designed into systems to maintain reasonable performance. Now we have systems with more and more processes running in the background to support the extra complexity of our systems, so designers are adding extra processing cores and support for process scheduling.
Yet another form of complexity is involved with the user interface. The typical user (and especially the support personnel) now have to master many new options and features, and understand all of their interactions. This is increasingly difficult for someone of even above-average ability. It is no wonder that the average home user has myriad problems using their systems!
Of course, the security implications of all this complexity have been obvious for some time. Rather than address the problem head-on by reducing the complexity and changing development methods (e.g., use safer tools and systems, with more formal design), we have recently seen a trend towards virtualization. The idea is that we confine our systems (operating systems, web services, database, etc) in a virtual environment supported by an underlying hypervisor. If the code breaks…or someone breaks it…the virtualization contains the problems. At least, in theory. And now we have vendors providing chipsets with even more complicated instruction sets to support the approach. But this is simply adding yet more complexity. And that can’t be good in the long run. Already attacks have been formulated to take advantage of these added “features.”
We lose many things as we make systems more complex. Besides security and correctness, we also end up paying for resources we don’t use. And we are also paying for power and cooling for chips that are probably more powerful than we really need. If our software systems weren’t doing so much, we wouldn’t need quite so much power “under the hood” in the hardware.
Although one example is hardly proof of this general proposition, consider the results presented in 86 Mac Plus Vs. 07 AMD DualCore. A 21-year old system beat a current top-of-the-line system on the majority of a set of operations that a typical user might perform during a work session. On your current system, do a “ps” or run the task manager. How many of those processes are really contributing to the tasks you want to carry out? Look at the memory in use—how much of what is in use is really needed for the tasks you want to carry out?
Perhaps I can be accused of being a reactionary ( a nice word meaning “old fart:”), but I remember running Unix in 32K of memory. I wrote my first full-fledged operating system with processes, a file system, network and communication drivers, all in 40K. I remember the community’s efforts in the 1980s and early 1990s to build microkernels. I remember the concept of RISC having a profound impact on the field as people saw how much faster a chip could be if it didn’t need to support complexity in the instruction set. How did we get from there to here?
Perhaps the time is nearly right to have another revolution of minimalism. We have people developing low-power chips and tiny operating systems for sensor-based applications. Perhaps they can show the rest of us some old ideas made new.
And for security? Well, I’ve been trying for several years to build a system (Poly^2) that minimalizes the OS to provide increased security. To date, I haven’t had much luck in getting sufficient funding to really construct a proper prototype; I currently have some funding from NSF to build a minimal version, but the funding won’t allow anything close to a real implementation. What I’m trying to show is too contrary to conventional wisdom. It isn’t of interest to the software or hardware vendors because it is so contrary to their business models, and the idea is so foreign to most of the reviewers at funding agencies who are used to build ever more complex systems.
Imagine a system with several dozen (or hundred) processor cores. Do we need process scheduling and switching support if we have a core for each active process? Do we need virtual memory support if we have a few gigabytes of memory available per core? Back in the 1960s we couldn’t imagine such a system, and no nation or company could afford to build one. But now that wouldn’t even be particularly expensive compared to many modern systems. How much simpler, faster, and more secure would such a system be? In 5 years we may be able to buy such a system on a single chip—will we be ready to use it, or will we still be chasing 200 million line operating systems down virtual rat holes?
So, I challenge my (few) readers to think about minimalism. If we reduce the complexity of our systems what might we accomplish? What might we achieve if we threw out the current designs and started over from a new beginning and with our current knowledge and capabilities?
[Small typo fixed 6/21—thanks cfr]
Copyright © 2007 by E. H. Spafford
[posted with ecto]
[tags]phishing, web redirection[/tags]
Jim Horning suggested a topic to me a few weeks ago as a result of some email I sent him.
First, as background, consider that phishing and related frauds are increasingly frequent criminal activities on the WWW. The basic mechanism is to fool someone into visiting a WWW page that looks like it belongs to a legitimate organization with which the user does business. The page has fields requesting sensitive information from the user, which is then used by the criminals to commit credit card fraud, bank fraud or identity theft.
Increasingly, we have seen that phishing email and sites are also set up to insert malware into susceptible hosts. IE on Windows is the prime target, but attacks are out there for many different browsers and systems. The malware that is dropped can be bot clients, screen scrapers (to capture keystrokes at legitimate pages), and html injectors (to modify legitimate pages to ask for additional information). It is important to try to keep from getting any of this malware onto your system. One aspect of this is to be careful clicking on URLs in your email, even if they seem to come from trusted sources because email can be spoofed, and mail can be sent by bots on known machines.
How do you check a URL? Well, there are some programs that help, but the low-tech way is to look at the raw text of a URL before you visit it, to ensure that it references the site and domain you expected.
But consider the case of short-cut URLs. There are many sites out there offering variations on this concept, with the two I have seen used most often being “TinyURL” and “SnipURL”. The idea is that if you have a very long URL that may get broken when sent in email, or that is simply too difficult to remember, you submit it to one of these services and you get a shortened URL back. With some services, you can even suggest a nickname. So, for example, short links to the top level of my blog are <http://tinyurl.com/2geym5>, <http://snipurl.com/1ms17> and <http://snurl.com/spafblog>.
So far, this is really helpful. As someone who has had URLs mangled in email, I like this functionality.
But now, let’s look at the dark side. If Jim gets email that looks like it is from me, with a message that says “Hey Jim, get a load of this!” with one of these short URLs, he cannot tell by looking at the URL whether it points somewhere safe or not. If he visits it, it could be a site that is dangerous to visit (Well, most URLs I send out are dangerous in one way or another, but I mean dangerous to his computer. 
). The folks at TinyURL have tried to address this by adding a feature so that if you visit <http://preview.tinyurl.com/2geym5> you will get a preview of what the URL resolves to; you can set this (with cookies) as your default. That helps some.
But now step deeper into paranoia. Suppose one of these sites was founded by fraudsters with the intent of luring people into using it. Or the site gets acquired by fraudsters, or hijacked. The code could be changed so that every time someone visits one of these URLs, some code at the redirect site determines the requesting browser, captures some information about the end system, then injects some malicious javacode or ActiveX before passing the connection to the “real” site. Done correctly, this would result in largely transparent compromise of the user system. According to the SnipURL statistics page, as of midnight on May 30th there have been nearly a billion clicks on their shortened URLs. That’s a lot of potential compromises!
Of course, one of the factors to make this kind of attack work is for the victim to be running a vulnerable browser. Unfortunately, there have been many vulnerabilities found for both IE and Firefox, as well as some of the less well-known browsers. With users seeking more functionality in their browsers, and web designers seeking more latitude in what they deliver, we are likely to continue to see browser exploits. Thus, there is likely to be enough of a vulnerable population to make this worthwhile. (And what browser are you using to read this with?)
I should make it clear that I am not suggesting that any of these services really are being used maliciously or for purposes of fraud. I am a happy and frequent user of both TinyURL and SnipURL myself. I have no reason to suspect anything untoward from those sites, and I certainly don’t mean to suggest anything sinister. (But note that neither can I offer any assurances about their motives, coding, or conduct.) Caveat emptor.
This post is simply intended as commentary on security practices. Thinking about security means looking more deeply into possible attack vectors. And one of the best ways to commit such attacks is to habituate people into believing something is safe, then exploiting that implicit trust relationship for bad purposes.
Hmm, reminds me of a woman I used to date. She wasn’t what she appeared, either…. But that’s a story for a different post.
[posted with ecto]
[tags]viruses,OpenOffice,Word,Microsoft,Office,Powerpoint,Excel[/tags]
In my last post, I ranted about a government site making documents available only in Word. A few people have said to me “Get over it—use OpenOffice instead of the Microsoft products.” The problem is that those are potentially dangerous too—there is too much functionality (some of it may be undocumented, too) in Word (and Office) documents.
Now, we have a virus specific to OpenOffice. We’ve had viruses that run in emulators, too. Trying to be compatible with something fundamentally flawed is not a security solution. That’s also my objection to virtualization as a “solution” to malware.
I don’t mean to be unduly pejorative, but as the saying goes, even if you put lipstick on a pig, it is still a pig.
Word and the other Office components are useful programs, but if MS really cared about security, they would include a transport encoding that didn’t include macros and potentially executable attachments—and encourage its use! RTF is probably that encoding for text documents, but it is not obvious to the average user that it should be used instead of .doc format for exchanging files. And what is there for Excel, Powerpoint, etc?
[tags]DHS,MS Word,threats[/tags]
Earlier, I wrote about the security risks of using Microsoft Word documents as a presentation and encoding format for sending files via email (see posts here and here). Files in “.doc” format contain macros, among other things, that could be executable. They also have metadata fields that might give away sensitive information, and a lot of undocumented cruft that may be used in the process of exploiting security. It is no wonder that exotic exploits are showing up for Word documents. And only today it was revealed that the latest version of Office 2007 may not have even gotten the most recent patch set.
Want to find some vulnerabilities in Word? Then take a look at the list of US-CERT alerts on that software; my search returns almost 400 hits. Some of these are not yet patched, and there are likely many as-yet unpatched flaws still in there.
Clearly, the use of Word as a document exchange medium is Bad (that’s with a definite capital B). People who understand good security practices do not exchange Word files unless they are doing collaborative editing, and even then it is better to use RTF (if one continues to be beholden to Microsoft formats). Good security hygiene means warning others, and setting a good example.
Now, consider that DHS has released BAA07-09 to solicit research and prototypes to get fixes for current cyber infrastructure vulnerabilities. I could rant about how they claim it is for R&D but is really a BAA for further product development for fundamentally flawed software that cannot be fixed. But that isn’t the worst part. No, the BAA is only available as Word documents!
Can you say “irony”? This is the agency charged with helping guide us to a more secure infrastructure? If so, electronically KYAG.
Update: A response from Dr. Douglas Maughn at DHS points out that the site I indicated for the BAA is actually FedBizOps rather than DHS. The DHS posting site actually has it in PDF…although the FedBizOps link is the one I’ve seen in several articles (and in a posting in SANS NewsBites).
Of course, it would be great if DHS could get the folks at FedBizOps to clean up their act, but at least in this case, DHS—or rather, DHSARPA—got it right. I stand corrected.
