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Centers of Academic .... Adequacy
History
Back in 1997, the year before CERIAS was formally established, I testified before Congress on the state of cyber security in academia. In my testimony, I pointed out that there were only four established research groups, and their combined, yearly PhD production was around 3 per year, not counting cryptography.
Also in that testimony, I outlined that support was needed for new centers of expertise, and better support of existing centers.
As a result of that testimony, I was asked to participate in some discussions with staff from OSTP, from some Congressional committees (notably, the House Science Committee), and Richard Clarke's staff in the Executive Office of the President. I was also invited to some conversations with leadership at the NSA, including the deputy director for information security systems (IAD) (Mike Jacobs). Those discussions were about how to increase the profile of the area, and get more people educated in information security.
Among the ideas I discussed were ones expanded from my testimony. They eventually morphed into the Scholarship for Service program, the NSF CyberTrust program, and the NSA Centers of Academic Excellence (CAE). [NB. I am not going to claim sole or primary credit for these programs. I know I came up with the ideas, briefed people about them, discussed pros & cons, and then those groups took them and turned them into what we got. None of them are quite what I proposed, but that is how things happen in DC.]
The CAE program was established by the NSA in late 1998. The CAE certification was built around courses meeting CNSS requirements. Purdue was one of the first seven universities certified as CAEs, in May of 1999. We remained in the CAE program until earlier this year (2008). In 2003, DHS became a co-sponsor of the program.
Why Purdue is No Longer a CAE
In 2007, we were informed that unless we renewed our CNSS certifications by the end of August, we would not be eligible for CAE renewal in 2008. This prompted discussion and reflection by faculty and staff at CERIAS. As noted above, the mapping of CNSS requirements to our classes is non-trivial. The CAE application was also non-trivial. None of our personnel were willing to devote the hours of effort required to do the processing. Admittedly, we could have "faked" some of the mapping (as we know some schools have done in the past), but that was never an option for us. We had other objections, too (see what follows).As a result, we did not renew the certifications, and we dropped out of the CAE program when our certification expired earlier this year.
Our decision was not made lightly -- we nearly dropped out in 2004 when we last renewed (and were not grandfathered into the new 5 year renewal cycle, much to our annoyance), and there was continuing thought given to this over intervening years. We identified a number of issues with the program, and the overhead of the mapping and application process was not the only (or principal) issue.
First, and foremost, we do not believe it is possible to have 94 (most recent count) Centers of Excellence in this field. After the coming year, we would not be surprised if the number grew to over 100, and that is beyond silly. There may be at most a dozen centers of real excellence, and pretending that the ability to offer some courses and stock a small library collection means "excellence" isn't candid.
The program at this size is actually a Centers of Adequacy program. That isn't intended to be pejorative -- it is simply a statement about the size of the program and the nature of the requirements.
Some observers and colleagues outside the field have looked at the list of schools and made the observation that there is a huge disparity among the capabilities, student quality, resources and faculties of some of those schools. Thus, they have concluded, if those schools are all equivalent as "excellent" in cyber security, then that means that the good ones can't be very good ("excellent" means defining the best, after all). So, we have actually had pundits conclude that cyber security & privacy studies can't be much of a discipline. That is a disservice to the field as a whole.
Instead of actually designating excellence, the CAE program has become an ersatz certification program. The qualifications to be met are for minimums, not for excellence. In a field with so few real experts and so little money for advanced efforts, this is understandable given one of the primary goals of the CAE program -- to encourage schools to offer IA/IS programs. Thus, the program sets a relatively low bar and many schools have put in efforts and resources to meet those requirements. This is a good thing, because it has helped raise the awareness of the field. However, it currently doesn't set a high enough bar to improve the field, nor does it offer the resources to do so.
Setting a low bar also means that academic program requirements are being heavily influenced by a government agency rather than the academic community itself. This is not good for the field because it means the requirements are being set based on particular application need (of the government) rather than the academic community's understanding of foundations, history, guiding principles, and interaction with other fields. (E.g., Would your mathematics department base its courses on what is required to produce IRS auditors? We think not!) In practice, the CAE program has probably helped suppress what otherwise would be a trend by our community to discuss a formal, common curriculum standard. In this sense, participation in the CAE program may now be holding us back.
Second, and related, the CNSS standards are really training standards, and not educational standards. Some of them might be met by a multi-day class taught by a commercial service such as SANS or CSI -- what does that say about university-level classes we map to them? The original CNSS intent was to provide guidance for the production of trained system operators -- rather than the designers, researchers, thinkers, managers, investigators and more that some of our programs (and Purdue's, in particular) are producing.
We have found the CNSS standards to be time-consuming to map to courses, and in many cases inappropriate, and therefore inappropriate for our students. Tellingly, in 9 years we have never had a single one of our grads ask us for proof that they met the CNSS standards because an employer cared! We don't currently intend to offer courses structured around any of the CNSS standards, and it is past the point where we are interested in supporting the fiction that they are central to a real curriculum.
Third, we have been told repeatedly over the years that there might be resources made available for CAE schools if only we participated. It has never happened. The Scholarship for Service program is open to non-CAE schools (read the NSF program solicitation carefully), so don't think of that as an example. With 100 schools, what resources could reasonably be expected? If the NSA or DHS got an extra $5 million, and they spread it evenly, each would get $50,000. Take out institutional overhead charges, and that might be enough for 1 student scholarship...if that. If there were 10 schools, then $500,000 each is an amount that might begin to make a difference. But over a span of nearly 10 years the amount provided has been zero, and any way you divide that, it doesn't really help any of us. Thus, we have been investing time and energy in a program that has not brought us resources to improve. Some investment of our energy & time to bolster community was warranted, but that time is past.
Fourth, the renewal process is a burden because of the nature of university staffing and the time required. With no return on getting the designation, we could not find anyone willing to invest the time for the renewal effort.
Closing Comments
In conclusion, we see the CAE effort as valuable for smaller schools, or those starting programs. By having the accreditation (which is what this is, although it doesn't meet ISO standards for such), those programs can show some minimal capabilities, and perhaps obtain local resources to enhance them. However, for major programs with broader thrusts and a higher profile, the CAE has no real value, and may even have negative connotations. (And no, the new CAE-R program does not solve this as it is currently structured.)
The CAE program is based on training standards (CNSS) that do not have strong pedagogical foundations, and this is also not appropriate for a leading educational program. As the field continues to evolve over the next few years, faculty at CERIAS at Purdue expect to continue to play a leading role in shaping a real academic curriculum. That cannot be done by embracing the CAE.
We are confident that people who understand the field are not going to ignore the good schools simply because they don't have the designation, any more than people have ignored major CS programs because they do not have CSAB accreditation. We've been recognized for our excellence in research, we continue to attract and graduate excellent students, and we continue to serve the community. We are certain that people will recognize that and respond accordingly.
More importantly, this goes to the heart of what it means to be "trustworthy." Security and privacy issues are based on a concept of trust and that also implies honesty. It simply is not honest to continue to participate in (and thereby support) a designation that is misleading. There are not 94 centers of excellence in information and cyber security in the US. You might ask the personnel at some of the schools that are so designated as to why they feel the need to participate and shore up that unfortunate canard.
The above was originally written in 2008. A few years later, the CAE requirements were changed to add a CAE-R designation (R for research), and several of our students did the mapping so we were redesignated. Most of the criticisms remain accurate even in 2012.
Who ya gonna call?
This morning I received an email, sent to a list of people (I assume). The subject of the email was "Computer Hacker's service needed" and the contents indicated that the sender was seeking someone to trace back to the sender of some enclosed email. The email in question? The pernicious spam email purporting to be from someone who has been given a contract to murder the recipient, but on reflection will not do the deed if offered a sum of money.
This form of spam is well-known in most of the security and law enforcement communities, and there have been repeated advisories and warnings issued to the public. For instance, Snopes has an article on it because it is so widespread as to have urban legend status. The scam dates back at least to 2006, and is sometimes made to seem more authentic by including some personalized information (usually taken from online sources). A search using the terms "hitman scam spammer" returns over 200,000 links, most of the top ones being stories in news media and user alert sites. The FBI has published several alerts about this family of frauds, too. This is not a rare event.
However, it is not that the author of the email missed those stories that prompts this post. After all, it is not the case that each of us can be aware of everything being done online.
Rather, I am troubled that someone would ostensibly take the threat seriously, and as a follow-up, seek a "hacker" to trace the email back to its sender rather than report it to law enforcement authorities.
One wonders if the same person were to receive the same note on paper, in surface email, whether he would seek the services of someone adept at breaking into mail boxes to seek out the author? Even if he did that, what would it accomplish? Purportedly, the author of the note is a criminal with some experience and compatriots (these emails, and this one in particular, always refer to a gang that is watching the recipient). What the heck is the recipient going to do with someone -- and his gang -- who probably doesn't live anywhere nearby?
Perhaps the "victim" might know (or suspect) it is a scam, but is trying to aid the authorities by tracing the email? But why spend your own money to do something that law enforcement is perhaps better equipped to do? Plus, a "hacker" is not necessarily going to use legal methods that will allow the authorities to use the results. Perhaps even more to the point, the "hacker" may not want to be exposed to the authorities -- especially if they regularly break the law to find people!
Perhaps the victim already consulted law enforcement and was told it was a scam, but doesn't believe it? Well, some additional research should be convincing. Plus, the whole story simply isn't credible. However, if the victim really does have a streak of paranoia and a guilty conscience, then perhaps this is plausible. However, in this case, whoever is hired would likewise be viewed with suspicion, and any report made is going to be doubted by the victim. So, there is no real closure here.
Even worse, if a "hacker" is found who is willing to break the rules and the laws to trace back email, what is to say that he (or she) isn't going to claim to have found the purported assassin, he's real, and the price has gone up but the "hacker" is willing to serve as an intermediary? Once the money is paid, the problem is pronounced "fixed," This is a form of classic scam too -- usually played on the gullible by "mystics" who claim that the victim is cursed and can only be cured by a complicated ritual involving a lot of money offered to "the spirits."
Most important -- if someone is hired, and that person breaks the law, then the person hiring that "hacker" can also be charged under the law. Hiring someone to break the law is illegal. And having announced his intentions to this mailing list, the victim has very limited claims of ignorance at this point.
At the heart of this, I am simply bewildered how someone would attempt to find a "hacker" -- whose skill set would be unknown, whose honesty is probably already in question, and whose allegiances are uncertain -- to track down the source of a threat rather than go to legitimate law enforcement. I can't imagine a reasonable person (outside of the movies) receiving a threatening letter or phone call then seeking to hire a stranger to trace it back rather than calling in the authorities.
Of course, that is why these online scams -- and other scams such as the "419 scams" continue to work: people don't think to contact appropriate authorities. And when some fall for it, it encourages the spammers to keep on -- increasing the pool of victims.
(And yes, I am ignoring the difficulty of actually tracing email back to a source: that isn't the point of this particular post.)
Barack Obama, National Security, and Me
[Update 7/17: Video of the Senator's opening remarks and the panel session (2 parts) are now online at this site. I have also added a few links.]
This story (somewhat long) is about Senator Barack Obama's summit session at Purdue University today (Wednesday, July 16). on security challenges for the 21st century. I managed to attend, took notes, and even got my name mentioned. Here's the full story.
Prelude Monday night, I received email from a colleague here at Purdue asking if I could get her a ticket to see Senator Obama on campus. I was more than a little puzzled -- I knew of no visit from the Senator, and I especially didn't know why she thought I might have a ticket (although there are people around here who frequently ask me for unusual things). Another exchange of email resulted in the discovery that the Senator was coming to Purdue today (the 16th of July) with a panel to hold a summit meeting on security issues for the 21st century. Cyber security was going to be one of the topics. The press was told that Purdue was chosen because of the leading role our researchers have in various areas of public safety and national security -- including the leading program in cyber security -- although some ascribed political motives as the primary reason for the location. I found it rather ironic that security would be given as the reason for being at Purdue, and yet those of us most involved with those security centers had not been told about the summit or given invitations. It appears that the organizers gave a small number of tickets to the university, and those were distributed to administrators rather than faculty and students working in the topic areas. I found this all very ironic and interesting, and expressed as much in email to several friends and colleagues -- including several who I knew had some (indirect) link to the Senator's campaign. I had faint hope of getting a ticket, but was more interested in simply getting the word back that there was a misfire in the organization of the event. Late last night (I was in the office until 6:30) I got a call from someone associated with the Obama campaign. He apologized for the lack of an invitation, and informed me that a ticket was awaiting me at the desk the next day. The Event I went over to the Purdue Union at 11:30; the official event was to start at 12. I encountered a number of Purdue administrators in the crowd. Security was apparent for the event, including metal detectors at the door run by uniformed officers, some of whom I believe were with the Secret Service uniformed division. The officers everywhere were polite and cheerful, but watchful. I found a seat in the back of the North Ballroom with about 500 other guests...and nearly as many members of the press, entourage, ushers, protection detail, and so on. I won't try to summarize everything said by the Senator and panel -- you can find the full video here (in two parts). I will provide some impressions of specific things that were said. The event started almost on time (noon) with Senator Evan Bayh introducing Senator Barack Obama. Sen. Obama then read from a prepared set of remarks. His comments really resonated with the crowd (I encourage you to follow the link to read them). His comment about how we have been "fighting the last war" is particularly appropriate. He made some very nice comments about Senator Richard Lugar, the other Senator from Indiana. Senator Lugar is a national asset in foreign policy, and both Senators Obama and Bayh (and former Senator Nunn) had nothing but good things to say about him -- and all have worked with him on disarmament and peace legislation. One of the lighter moments was when Senator Obama said that Senator Lugar was a great man in every way except that he was a Republican! Early in his statement, he deviated from his script as reproduced in the paper, and dropped my name as he was talking about cyber security. I was very surprised. He referred to me as one of the nation's leading experts in cyber security when he mentioned Purdue being in the lead in this area. Wow! I guess someone I sent my email to pushed the right button (although my colleagues and our students deserve the recognition, as much or more than I do). His further comments on officially designating the cyber infrastructure as a strategic asset is important for policy & legal reasons, and his comments on education and research also seemed right on. It was a strong opening, and there was obviously a lot in his comments for a number of different audiences, including the press. Panel Part I The first 1/3 of the panel discussion was on nuclear weapons issues. The experts present to talk on the issue were (former) Senator Sam Nunn (who joked that in Indiana everyone thought his last name was actually Nunn-Lugar), Senator Bayh, and Dr. Graham Allison, the director of the Belfer Center at Harvard. There was considerable discussion about the proliferation of nuclear materials, the need for cooperation with other countries rather than ignoring them (viz. North Korea and Iran), and the control of fissionable material. There were some statements that I found to be a bit of hyperbole: For instance, the statement that a single bomb could be made by terrorists to destroy a whole city. Not to minimize the potential damage, but without sophisticated nation-state assistance and machining, a crude fission weapon is about all that a terrorist group could manage, and it wouldn't be that large or that easy to build. A few tens of kilotons of fission explosion could definitely ruin your day, but a detonation at ground level wouldn't destroy a whole city of any size. (Lafayette, IN would be mostly destroyed by one, but that isn't a major city.) Plutonium is too dangerous to handle, so over 100 pounds of U-235 (or U-233) would be needed, and machined appropriately, for such a weapon. Without accelerators and specially shaped charges & containers, getting fission fast enough and long enough is difficult and....well, there is a very serious threat, and the nuances may be lost on the average crowd, but the focus on terrorists building a significant bomb seemed wrong to me. There were some excellent remarks made about opportunity cost. For instance, the one figure that stood out was that we could fully fund the Nunn-Lugar initiative and some other plans to secure loose nuclear materials by spending the equivalent of 1 month of what we now spend in Iraq over the next 4 years around the world; the war in Iraq is breeding terrorists and making US enemies, while securing loose nukes would help protect generations to come around the world. As both a taxpayer and a parent (as well as someone immersed in defense issues), I know where I would prefer to see the money spent! One other number given is that currently less than 1/4 of 1% of the defense budget is spent on containing nuclear materials, despite it being a declared priority of President Bush. Professor Allison said that despite grade inflation at Harvard, the President still gets an "F" in this area. Another interesting factoid stated was that about 10% of the lights in the US are powered by electricity generated from reprocessed fissile material taken from Russian nukes rendered safe under the Nunn-Lugar initiative. That sounds high to me given the amount of nuclear power generated in the US, but even if off by a factor of 10, darned impressive. Panel Part II The second part of the panel was on bio weapons. The panelists were Dr. Tara O'Toole of the Center for Biosecurity at Pitt, and Dr. David Relman of Stanford. Their discussion was largely what I expected, about how bio-weapons can be produced by rogue actors as well as rogue states. They made the usual references to plague (with a funny interchange about prairie dogs being carriers, and keeping the Senator's campaign away from them), anthrax and Ebola. Again, there was a bit of exaggeration coupled with the dialog. It was pointed out that there has still been no apprehension of the perpetrator of the 2001 anthrax attacks. It was then stated that the anthrax in the envelope sent to Senator Daschle was enough to kill a billion people. No mention was made about how impossible it would be to meter and deliver such dosages in the most appropriate manner to achieve that. In fact, no discussion was made about the difficulty in weaponizing most biological agents, limiting their use as a targeted weapon over a large area. And furthermore, no mention at all was made of chemical weapons. The conclusion here was that investment in better research and international cooperation was key. The statement was made that better integration of electronic health records would be important, too, although some studies I recall indicate that their utility is probably not so great as some would hope. It was also concluded that benefits in faster medical response and better vaccine production would help in non-crisis times as well. I don't think we can argue too much with that, although the whole issue of how we pay for medicine and health issues looms large. Panel Part III The last panel featured Alan Wade, former CIO of the CIA, and Paul Kurtz of Good Harbor Consulting, speaking on the cyber threat. I've known Paul for years, and he is a great person to talk on these issues. The fact that cyber technology is universal and ubiquitous was highlighted. So was the asymmetry inherent in the area. Some mention was made about how nothing has been done by the current administration until very recently. Sadly, that is clearly the case. The National Strategy in 2002, the PITAC report in 2005, and the CSTB report in 2007 (to name 3 examples) all generated no response. As a member of the PITAC that helped write the 2005 report, I was shocked at the lack of Federal investment and the inaction we documented (I knew it was bad, but didn't realize until then how bad it was); the reaction from the White House was to dissolve the committee rather than address the real problems highlighted in the report. As one of today's panelists put it -- the current administration's response has been "...late, fragmented, and inadequate." Amen. I was disappointed that so much was said about terrorism and denial of service. Paul did join in near the end and point out that alteration of critical data was a big concern, but there was no mention of alteration of critical services, about theft of intellectual property, about threats to privacy, or other more prominent threats. Terrorism online is not the biggest threat we face, and we have a major crisis in progress that doesn't involve denial of service. We need to ensure that our policymakers understand the scope of the threat. On the plus side, Senator Obama reiterated how he sees cyber as a national resource and critical infrastructure. He wants to appoint a national coordinator to help move protection forward. (If he is elected I hope he doesn't put the position in DHS!) Paul pointed out the need for more funds for education and research. He also made a very kind remark, mentioning me by name, and saying how we were a world-class resource built with almost no funding. That's not quite true, but sadly not far off. I have chafed for years at how much more we could do with even modest on-going support that wasn't tied to specific research projects.... Conclusions I was really quite impressed with the scope of the discussion, given the time and format, and the expertise of the panelists. Senator Obama was engaged, attentive, and several of his comments and questions displayed more than a superficial knowledge of the material in each area. Given our current President referring to "the Internets" and Senator McCain cheerfully admitting he doesn't know how to use a computer, it was refreshing and hopeful that Senator Obama knows what terms such as "fission" and "phishing" mean. And he can correctly pronounce "nuclear"! :-) His comments didn't appear to be rehearsed -- I think he really does "get it." (Before someone picks on me too much.... I believe Senator McCain is an honorable man, a dedicated public servant, and a genuine American hero. I am grateful to have people like him intent on serving the public. However, based on his comments to the press and online, I think he is a generation out of date on current technology and important related issues. That isn't a comment related to his age, per se, but to his attitude. I'd welcome evidence that I am mistaken.) Senator Obama is a great orator. I also noticed how his speed of presentation picks up for the press (his opening remarks) but became more conversational during the panel. Senator Obama kept bringing the panel back to suggestions about what could be done to protect the nation. I appreciated that focus on the goal. He also kept returning to the idea that problems are better solved early, and that investments without imminent threat are a form of insurance -- paying for clean-up is far greater than some prudent investment early on. He also repeatedly mentioned the need to be competitive in science and technology, and how important support for education is -- and will be. After the session was over, I didn't get a chance to meet any of the campaign staff, or say hello to Paul. I did get about 90 seconds with Senator Bayh and invited him to visit. After my name had been mentioned about 3 times by panelists and Senator Obama, he sort of recognized it when I introduced myself. We'll see if he follows up. I've visited his office and Senator Lugar's, repeatedly, and neither have ever bothered to follow up to see what we're doing or whether they could help. Several people in the audience commented on my name being mentioned. I'm more than a little embarrassed that they didn't refer to CERIAS and my colleagues, and in fact I was the only Purdue person mentioned by name during the entire 2 hours, and then it happened multiple times. I'm not sure if that's good or not -- we'll see. However, as P.T. Barnum said, there's no such thing as bad publicity ... so long as they spell my name correctly. %-P None of the local or national press seem to have picked it up, however, so even spelling isn't an issue. The press, in fact, hasn't seemed to focus on the substance of the summit at all. I've read about 15 accounts so far, and all have focused on his choice of VP or the status of the campaign. It is so discouraging! These are topics of great importance that are not well understood by the public, and the press simply ignores them. Good thing Angelina Jolie gave birth earlier in the week or the summit wouldn't have even made the press. :-S I wish more of the population would take the time to listen to prolonged discussion like this. 15-second sound bites serve too often as the sole input for most voters. And even then, too many are insufficiently educated (or motivated) to understand even the most basic concepts. I wonder if more than 5 people will even bother to read this long a post -- most people want blogs a single page in length. As for my own political opinions and voting choices, well, I'm not going to use an official Purdue system to proselytize about items other than cyber security, education, research and Purdue. You can certainly ask me if you see me. Now, if only I had confidence in the electronic voting equipment that so many of us are going to be forced to use in November (hint: I'm chair of the USACM). Last Tongue-in-Cheek Word And no, I'm not particularly interested in the VP position.
Virtualization Is Successful Because Operating Systems Are Weak
- Availability
- Minimized downtime for patching OSes and applications
- Restart a crashed OS or server
- Scalability
- More or different images as demand changes
- Isolation and compartmentalization
- Better hardware utilization
- Hardware abstraction for OSes
- Support legacy platforms
- Availability
- Minimized downtime for patching applications
- Restart crashed applications
- Scalability
- More or different processes as demand changes
- Isolation and compartmentalization
- Protected memory
- Accounts, capabilities
- Better hardware utilization (with processes)
- Hardware abstraction for applications
VMWare ESX Server runs its own OS with drivers. Xen and offerings based on it have a full, general purpose OS in domain 0, in control and command of the VMM (notwithstanding disaggregation). Microsoft's "Hyper-V" requires a full-blown Windows operating system to run it. So what we're doing is really exchanging an untrusted OS for another, that we should trust more for some reason. This other OS also needs patches, configuration and maintenance. Now we have multiple OSes to maintain! What did we gain? We don't trust OSes but we trust "virtualization" that depends on more OSes? At least ESX is "only" 50 MB, simpler and smaller than the others, but the number of defects/MB of binary code as measured by patches issued is not convincing.
I'm now not convinced that a virtualization solution + guest OS is significantly more secure or functional than just one well-designed OS could be, in theory. Defense in depth is good, but the extent of the spread of virtualization may be an admission that we don't trust operating systems enough to let them stand on their own. The practice of wiping and reinstalling an OS after an application or an account is compromised, or deploying a new image by default suggests that there is little trust in the depth provided by current OSes.
As for ease of management and availability vs patching, I don't see why operating systems would be unable to be managed in a smart manner just like ESX is, migrating applications as necessary. ESX is an operating system anyway... I believe that all the special things that a virtualization solution does for functionality and security, as well as the "new" opportunities being researched, could be done as well by a trustworthy, properly designed OS; there may be a thesis or two in figuring out how to implement them back in an operating system.
What virtualization vendors are really doing is a clever way to smoothly replace one operating system with another. This may be how an OS monopoly could be dislodged, and perhaps would explain the virtualization-unfriendly clauses in the licensing options for Vista: virtualization could become a threat to the dominance of Windows, if application developers started coding for the underlying OS instead of the guest. Of course, even with a better OS we'd still need virtualization for testbeds like ReAssure, and for legacy applications. Perhaps ReAssure could help test new, better operating systems.
(This text is the essence of my presentation in the panel on virtualization at the 2008 CERIAS symposium).
Related reading:
Heiser G et al. (2007) Towards trustworthy computing systems: Taking microkernels to the next level. ACM Operating Systems Review, 41
Tanenbaum AS, Herder JN and Bos H (2006) Can we make operating systems reliable and secure? Computer, 39


