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Summary of July 15th, 2020 Purdue Seminar on Control System Cyber Security

Joe Weiss

Guest Blog by Joe Weiss, Applied Control Systems, Inc

Wednesday July 15, 2020 I gave a 1 hour presentation on control system cyber security for the Purdue University Summer Seminar Series.


The statistics from the call include:

There were 183 pre-registrations of which 119 attended. The registrations were from 16 countries – Australia, Austria, Brazil, China, Germany, India, Israel, Kuwait, Lithuania, Mexico, Netherlands, New Zealand, Saudi Arabia, Singapore, UK, US. Actual attendees were from India, Israel, Kuwait, Lithuania, Mexico, Netherlands, Saudi Arabia, Singapore, UK, US.

For those unable to attend, the recording will be on the Purdue Cerias website at: https://ceri.as/weiss

After 20 years, control system cyber security has made significant strides in monitoring and securing OT (control system) networks. However, after 20 years, control system cyber security has made minimal strides in monitoring or securing the actual control system devices (e.g., process sensors, actuators, drives, analyzers, etc.) and lower level device networks which is where you go “boom in the night”. Much of this is because of the culture clash between the engineering community who understand the devices but generally have been removed form control system cyber security efforts and the network security personnel who do not understand control system devices or control system processes. The impact of the culture gap is at least partially due to network security’s erroneous assumptions:

  • Process sensor input to all OT networks are uncompromised, authenticated, and correct so that securing the network packers is sufficient to protect the control systems and physical processes,
  • control system devices can only be accessed from Ethernet (IP) network,
  • all control system anomalies can be found from Ethernet (IP) network,
  • network vulnerabilities directly correspond to physical system impacts,
  • cyber security frameworks can be directly applied to control system cyber security, and
  • cyber security is about zero trust.


There were 10 questions raised that I did not have a chance to answer on the webinar. I thought the questions and answers would be of general interest.

1). Q: Joe, this is great. You said "Our information sharing doesn't work." What do you think needs to be improved, and how would you improve it?

Answer: Information sharing on cyber network vulnerabilities are addressed in DHS and vendor disclosures as well as industry ISACs. The information sharing that is missing is about actual cyber-related incidents. NERC Lessons Learned don’t address incidents as being cyber-related. The various industry ISACs have not addressed cyber incidents occurring within their industry. The sharing on control system incidents to date most often has been by engineers who have seen incidents that were out of the ordinary. Informally, my old conference (ICS Cyber Security Conference which no longer exists) served as an informal information sharing vehicle for the engineers to discuss real control system cyber-related incidents. Unfortunately, I don’t believe the government can help because of the private organizations concern about making these incidents public. I wrote a chapter in my book, Protecting Industrial Control Systems from Electronic Threats Chapter 9 “Information Sharing and Disclosure”. I will have more to say about this subject in a separate blog at www.controlglobal.com/unfettered.

2). Q: What is your view on Executive order for going back to analog system? We are all driving through zero carbon and digitalization- How to achieve the balance between them?

Answer: Hardwired analog systems with no “intelligence” such as electromechanical float switches as part of a hard-wired relay ladder logic system would be independent of a cyber attack from external threat agents, including hardware backdoors. However, adding any intelligence and modern communication capabilities would make the analog systems as vulnerable as digital systems to a backdoor sensor attack. Both smart and dumb systems would be potentially vulnerable with respect to a physical, hands on insider attack. That is the reason for defense-in-depth. The only way to get the balance between zero carbon and digitalization (or manufacturing and digitalization) is to have engineering and network security work the issues together.

3). Q: What approach do we take to secure level 0 and level 1 equipment?

Answer: I mentioned in my presentation that a major misconception is that all process sensor communications have traverse the Ethernet IP network and that network monitoring can identify any sensor anomalies. Consequently, there is a need to develop control system policies, procedures, and use existing equipment (as well as network) monitoring technologies. However, existing equipment or network monitoring technologies likely will not be sufficient to identify counterfeit devices or address hardware backdoors. This would most likely require new sensor monitoring technology that address the “physics” of the sensors which would be the input to both equipment and network monitoring. This new sensor monitoring technology has been proven in laboratory testing against multiple sensor vendors. In addition, there needs to be an industry recognition that the requirements within standards like ISA 62443 apply to the entire control system, level 0 through to the DMZ. Part of this understanding is that the control system and its network is owned by engineering personnel (operations, engineering support, maintenance) rather than the IT personnel, who should be used in a support role as a service provider.

4). Q: So to keep validating the low-level sensor data real time, we will need to know the algorithm that computes the result (e.g., temperature, pressure, etc.) but manufacturers may not wish to share their proprietary algorithms. Then, what can be done?

Answer: The sensors need to be identified by physics “fingerprinting” (see above). This would identify counterfeits as well as identify any sensor deviations agnostically. That is, it will identify deviations whether from sensor drift, loose screws, calibration issues, hardware problems, or cyber compromises. Once the deviation is identified, there are available tools that should be capable of determining the cause. It is a shame to say in 2020 we still don’t know when to use our diagnostic toolboxes because of the lack of awareness.

5). Q: Could you also have an engineer's SOC rather than an IT/OT SOC.? They would focus on the engineering aspects.

Answer: Without being flippant, that is the control room or control center.

6). Q: How to mitigate supply chain risks?

Answer: This is a very complex question because supply chain risks can range from an entire device to software, to firmware, to microprocessors, as well as integration of multiple instances of these. It requires the cooperation of procurement, physical security, cyber security, test shops/labs, engineering, and maintenance. Sensor monitoring to detect counterfeit or hardware backdoors would be a critical piece of the solution. Asset owners should also require their product and service providers to comply with standards like ISA 62443-2-4 and then to vet them against those requirements. I would be happy to further discuss my thoughts offline.

7). Q: Two questions : Is there any validated OT architecture that may hinder the possibility of backdoor attacks where the device would look for a master to trigger?

Answer: I don’t think so as the backdoor could bypass the OT architecture – the reason for the Presidential Executive Order.

8). Q: I had a question about the levels. Do you think there is an advantage in separating level-0 devices to continuously-monitored devices (PLCs, HMIs) and smart IO Devices (IO Link based devices, Ethernet IP devices/Profinet devices)

Answer: Two years ago, we created a special ISA99 Working Group on Level 0,1 devices – ISA99.04-07 to address Level 0,1 devices. The working group concurred that “legacy“ Level 0,1 devices cannot be secured to current cyber security requirements. Additionally, the Purdue Reference Model was identified as being out-of-date for addressing modern control system device technology for cyber and communication capabilities as there no longer are clear distinctions between levels even for the same device. There is an advantage to segregating sensors based on the zone they are located. Each zone should have its security requirements based on risk and countermeasures that are unique to that zone. For instance, a safety-instrumented system (SIS) involves sensors, logic solver, final elements as well as an engineering workstation. Having a SIS zone makes it easier to accomplish least privilege from both a physical and logical access perspective.

9). Q: Are Controls devices companies taking any action to certify programmable hardware electronics to validate no malicious logic is included on logic or printed circuit hardware?

Answer: I think that is the ultimate intent of ISASecure and commercial test/certification companies. The devices certified to date are controllers and master stations. None of the Level 0,1 devices has completed cyber security certifications.

10). Q: Another questions I had was about a recent change in the industry direction, to put all devices on the IP network now.¬ I bring new machines to our plant, and 100% of our machines have an Ethernet network and a NAT gateway to expose device.

Answer: Unfortunately, that is becoming a common practice especially with Industry4.0 and other digital upgrade initiatives. However, I believe there is a real need to question whether safety devices should be part of the overall integrated plant Ethernet network. Moreover, I think there needs to be a reassessment of the need to connect control system devices directly to the Internet without some form of proxy to shield them from public access.

-Joe Weiss

COAST, Machine names, Sun, and Microsoft


I received considerable feedback from people who read the last post on the history of the COAST Lab. Several people asked for more history, and a few former students volunteered some memories.

I'll do a few posts with some specific recollections. If others want to send stories to me or enter them in the comments, we may document a little history. Eventually, I'll get around to the formation of CERIAS and some history of that effort.

COAST & Computers

In the earliest days, we had limited funding to apply to our research infrastructure; my priority for funding was student support. Everyone had an account on CS departmental machines, but we were limited in what we could do -- especially those requiring kernel configuration. Recall that this was in the era of 1992-1997, so neither "cheap" PCs running a Linux clone nor VMs were available. We needed access to workstations and a server or two.

I had contacts at several companies, and Purdue -- having the oldest degree-granting CS department in the world -- was also reasonably well-connected with vendors. I reached out to several of them.

HP stepped up to donate a workstation, but it was underpowered, and we didn't have the money for expansion. As I recall, HP at the time wasn't interested in making a donation beyond what they had already provided. Later, we also got a steep discount on an office laser printer. HP had some very clear divisions internally, so even though several groups wanted to engage, the ones with spending authority weren’t going to help.

I also recall donations of some Intel-based machines (from Intel). Other big vendors of the time -- Sequent, IBM, Pyramid, DEC -- indicated that they weren't concerned with security, so we got nothing from them. (3 of the 4 are now out of business, so go figure.) [Correction: in 1997 we were loaned a Dec ALPHA workstation for about 6 months, but weren't allowed to keep it. It was the primary computation engine for the work that led to the Kerberos 4 flaw paper.]


The company that helped the most was Sun Microsystems. (The late) Emil Sarpa was one of the people at Sun who took particular interest in what we were doing, although there were quite a few others there who interacted with us. (Mark Graff, head of their response team was one I remember, in particular.)

I don't recall if Emil was among our first contacts at Sun, but he quickly became an internal champion for us as their Manager of External Research Relations. He helped arrange some donations of equipment in return for (a) research results, and (b) access to potential hires. (That has long been the standard quid pro quo for collaboration with universities.).

Over time, including time as CERIAS, we received many workstations, a server, a lab of Sun Rays, a SunScreen firewall, and even some Java rings and readers. In return, Sun got quite a few reports of issues they could fix in their systems, and dozens of hires.


With upwards of two dozen machines in the lab we needed hostnames for all the computers. CS used names from the Arthurian legends for their machines. We knew that the CS department at Wisconsin used names of cheeses, one university (Davis?) used names of wine varieties, and there were other themes in use elsewhere. I decided that we would use the names of places from myth, legend, and science fiction/fantasy. Not only were there many candidates, but the idea of us working from places that didn't exist seemed like a good inside joke. (This also related to my long-standing interest in using deception defensively.)

Thus, we started naming machines after non-existent places: yavin, narnia, dorsai, trantor, solaria, barnum, xanadu, atlantis, lilliput, and more. We had a few disagreements in the lab when new machines came in ("I want to have Endor!"), but they all resolved amicably. I bought an atlas of imaginary places to serve as additional source material. We never really lacked for new names. Many of those names are still in use today, although the machines have been replaced many times.

COAST received a server-class machine from Sun in the mid-1990s. It had lots more space and memory than anything we had seen before, so naturally, it was named "brobdingnag." It became our central file server and mail machine. However, it soon became apparent that some of the lab denizens couldn't recall how to spell it, and petitioned for an alias. Thus, an alternate name in the host table came into being: "basm," for "big-assed server machine." A server named "basm" still exists at CERIAS to this day.

We decided to use a different naming scheme for printers and named them after Lands in the Oz mythos. Kansas, Oz, and Ix were the three I remember, but we had more.


A few machine names, in particular, have a story associated with them. One of the Intel machines we received was running Windows, and we named it "hades." (We were not Windows fans at the time.) A few years into COAST -- I don't recall when -- we attracted attention and support of Microsoft, in the form of David Ladd. He was (at that time) involved in academic outreach.

David was visiting us and saw all the Sun machines. He asked if we had anything running Windows. Someone pointed to "hades." He didn't say anything about that, but a few weeks later, we received two new Windows machines, fully configured. They went online as "nifilheim" and "tartarus." On his next visit, David quietly noted the machines. A few weeks later, two more showed up. I think those became "hel" and "duzkah." At his next visit, I observed that we were at a university, and I had access to scholars of history, religion, and sociology. I think we got a few more machines periodically to test us, but they all got named in the same scheme.

That isn't to imply that our relationship with Microsoft was adversarial! To the contrary, it was collaborative. In fall 1996, when Windows Server NT 4 came out, I offered a special-topics penetration testing class. About two dozen people enrolled. Under NDA with Microsoft, we proceeded to poke and prod the OS while also reading some of the classic literature on the topic.

Within two days, the class had discovered that NT 4 failed spectacularly if you exhausted memory, disk space, or file descriptors. By the end of the semester, everyone had found at least 4 significant flaws -- significant meaning "crashed the system" or "gained administrative privileges." We thus reported about 100 security flaws to the Windows support team. At that time, Microsoft was not as concerned about security as they are today, so we were told (eventually) that about 80 of the reports were for "expected but undocumented behavior" that would not be addressed. (Those numbers are not exact as they are based on the best of my recollection, but they are about right on the ratio.) That class provided several grads who went to work for Microsoft, as well as at least two who went to work for national agencies. I have not offered the class since that time as there have always been higher-priority needs for my teaching.

Over the years, many COAST (and eventually, CERIAS) graduates went to work at Microsoft. David --and MS -- remained supportive of our efforts until he moved into a new position well into the CERIAS days.

A Test of Time: COAST and an award-winning paper


The Paper

IEEE Test of Time Award

Today, various awards were announced at the 41st IEEE Symposium on Security & Privacy, including Test of Time Awards. One of the papers recognized was "Analysis of a Denial of Service Attack on TCP," written by a group of my former students -- Christoph Schuba, Ivan Krsul, Markus Kuhn, Aurobindo Sundaram, Diego Zamboni -- and me. The paper originally appeared in the 1997 S&P conference.

The paperreported results of work done in the COAST Laboratory -- the precursor to CERIAS. In this post, I'll make a few comments about the paper, and provide a little history about COAST.

The Paper & Authors

When we received notice of the award, we were all a bit taken aback. 23 years? At the time, we were one of only two or three recognized academic groups working in cybersecurity (although that word had yet to be used). As such, we managed to attract over a dozen very talented students — including the other authors of this paper.

In the second half of 1996, several network denial-of-service attacks took place across the Internet. We discussed these at one of our regular lab meetings. I challenged the students to come up with ways to mitigate the problem, especially to protect our lab infrastructure. The first step involved replicating the attack so it could be studied. That only took the students a few days of effort.

After a week or two of further work, we had another group discussion that included the students presenting a detailed review of how the attack worked, using the TCP diagram as illustration. There was a discussion of some partial solutions that were disappointing in scale or efficacy. I remember suggesting that if they could model the attack as a state machine, a solution might be developed the same way — noting good and bad hosts.

Within a week, the students had coded a working prototype to test against our model attack. Thereafter, there was some extended tinkering and tuning, and a rush to produce a paper to submit to the conference. Purdue later obtained a patent (U.S. Patent 6725378) on the idea, although it was never licensed for use.

Thereafter, Christoph received his PhD in 1997 with work in firewalls and went on to a career leading to his current position as a Senior Security Architect at Apple Computer. Ivan received his PhD in 1998 with work on security vulnerability classification and he currently runs a company, Artexacta, that he founded in Bolivia. Markus finished his MS in 1997, and after completing his PhD at Cambridge, joined the faculty there. Robin finished his MS in 2017 and is now the Head of Information Assurance and Data Protection at RELX. Diego finished his PhD in 2001 with work in agent-based intrusion detection and is now an Enterprise Security Architect at Swisscom in Switzerland.

The COAST Laboratory

Purdue has a long history of being involved in cybersecurity. Notably, Dorothy E. R. Denning completed her Ph.D. at Purdue in 1975, with a thesis on secure information flow. She then became an assistant professor and offered a graduate course in Data Security, which has been offered continuously to this day as CS 555.

Dorothy was at Purdue until 1983. One of her notable students was Matt Bishop, who completed his M.S. and Ph.D. (1984) in information security on take-grant models. Matt has gone on to also be a major force in the field.

Sam Wagstaff joined the CS department in 1983 and took on the teaching of CS 555 after Dorothy left. His primary area of interest was cryptography, and he has had many notable discoveries and publications during his career at Purdue (Sam retired in 2019). He even has a form of prime number named after him: the Wagstaff Prime!

I joined Purdue's CS department in 1987. My primary research focus was in software engineering and distributed systems. I was involved with the newly-formed Software Engineering Research Center (SERC, an NSF-supported industry-university cooperative research center) at Purdue and the University of Florida. System security was a "hobby" area for me because there was not much of an interest in academia at the time other than in formal methods and cryptography. (I've discussed this elsewhere.)

In 1988, the Internet Worm incident occurred, as did my involvement in responding to it. Soon after that, I was the lead author of the first English-language technical reference book on computer viruses and co-authored the 1st edition of Practical Unix Security with Simson Garfinkel. I also was doing some highly visible research, including the work with Dan Farmer on COPS.

My work in the SERC had resulted in some great results, but I never saw them transitioning into practice. Meanwhile, my work in security had some immediate impact. Thus, I gradually started moving the focus of my work to security. This change was a bit risky halfway to my tenure decision, but it was what I felt compelled to do. I continued my work in intrusion detection and began research in software forensics (my work started that as a formal field).

The increased visibility of security also meant that some good students were coming to Purdue to work in the field and that some external funding started becoming available. Most of the students wanted to build systems-oriented security tools, but we knew there was potential for a very wide set of topics. So, Sam and I decided to form a laboratory within the CS department. The department head at the time, John Rice, gave us a room for the lab and encouraged us to seek out funding.

The COAST name

We knew that we needed a catchy name for the group. I threw it out as a challenge to a few of my students. Steve Chapin (now at LLNL) -- who was my first Ph.D. student in a security-related topic -- came up with COAST as an acronym for "Computer Operations, Audit, and Security Technologies." It also was a sarcastic reference to how funding agencies thought good computer science only occurred at the coasts. We knew immediately it was the perfect name, and we seldom used anything except for the acronym itself.

I, along with a couple of the students, played a bit with the desktop publishing tools of the day (recall, it was 1992) and came up with the logo: logo

We knew that we needed funding to make the lab viable and keep the space. I approached several of the current partners of the SERC along with some other friends of the CS department to see if we could get some initial funding to support equipment purchases and support for the students. Four stepped forward: Sun Microsystems, Bell-Northern Telecom (BNR), Schlumberger Laboratories, and Hughes Laboratories.

We were open for business as of spring in 1992!

Over the next six years, COAST grew in faculty, students, and research, establishing itself as the largest research group in computing security in the country, reaching a peak research budget of over one million dollars per year (pretty good for its time).

COAST's success became notable for several innovative and groundbreaking projects, including the Tripwire tool, the IDIOT intrusion detection system, vulnerability classification work by Aslam and Krsul that influenced the CVE system, the first-ever papers describing software forensics by Krsul, Spafford, and Weeber, the discovery of a serious lurking Kerberos 4 encryption flaw by Dole and Lodin, and the firewall reference model by Schuba -- among others.

Next chapter

As COAST grew and added faculty from across the university, it was clear that it was more than Computer Science. Some of the CS faculty members were hostile to the work, dismissing it as "merely systems administration." (A few still have that attitude.) The CS Ph.D. qualifying exams of the time had mandatory exams in both theory of computation and numerical analysis (the department had its roots -- from 1962 -- in mathematics). Some of the faculty in those two areas were particularly unbending, and as a result, several very promising security grad students exited Purdue with only an M.S. degree. In retrospect, that worked out okay for all of them as they went on to stellar careers in government and industry, all paid much better than any of those professors!

Those factors, and others, led to the transformation of COAST into a university-wide institute, CERIAS, in May of 1998. I've discussed this elsewhere and may do a follow-on post with some of that history.

See some of the recollections in COAST, Machine names, Sun, and Microsoft.

Near the Root of Cybersecurity Dysfunction


I’ve been missing from the CERIAS blog for much of the last year+ as I enjoyed a long-overdue sabbatical.

While I was away, I was going through some materials in my account and found slides from a talk I was giving many years ago. I referenced those in a post back in February, entitled A Common Theme. I polished that up a little, gave it a few times, and then presented it in the CERIAS Security Seminar when I returned to campus this fall.

Basically, I attribute a large portion of why we continue to have problems in what we call “cybersecurity” is that we don’t have a precise—and agreed-upon—definition of “security.” Coupled with that, we don’t have agreed-upon characteristics, nor do we have well-defined metrics. The result is that we can’t tell if something addresses needs, we have no idea if the money we spent has made a difference that corresponds to the outlay, and we can’t compare different approaches. That is simply the start!

If you want to watch the presentation then visit this link. (Note that we have videos of presentations going back 15 years—over 400 videos—all available at no charge!)


Challenging Conventional Wisdom


In IT security ("cybersecurity") today, there is a powerful herd mentality. In part, this is because it is driven by an interest in shiny new things. We see this with the massive pile-on to new technologies when they gain buzzword status: e.g., threat intelligence, big data, blockchain/bitcoin, AI, zero trust. The more they are talked about, the more others think they need to be adopted, or at least considered. Startups and some vendors add to the momentum with heavy marketing of their products in that space. Vendor conferences such as the yearly RSA conference are often built around the latest buzzwords. And sadly, too few people with in-depth knowledge of computing and real security are listened to about the associated potential drawbacks. The result is usually additional complexity in the enterprise without significant new benefits — and often with other vulnerabilities, plus expenses to maintain them.

Managers are often particularly victimized by these fads as a result of long-standing deficiencies in the security space: we have no sound definition of security that encompasses desired security properties, and we, therefore, have no metrics to measure them. If a manager cannot get some numeric value or comparison of how new technology may make things better vs. its cost, the decision is often made on "best practice." Unfortunately, "best practice" is also challenging to define, especially when there is a lot of talk and excitement by people about vending the next new shiny thing. Additionally, enterprise needs are seldom identical, so “best” may not be uniform. If the additional siren call is heard about "See how it will save you money!" then it is nearly impossible to resist, even if the "savings" are only near-term or downright illusory.

This situation is complicated because so much of what we use is defective, broken, or based on improperly-understood principles. Thus, to attempt to secure it (really, to gain greater confidence in it) solutions that sprinkle magic pixie dust on top are preferred because they don't mean sacrificing the sunk cost inherent in all the machines and software already in use. Magic fairy dust is shiny, too, and usually available at a lower (initial) cost than actually fixing the underlying problems. So that is why we have containers on VMs on systems with multiple levels of hypervisor behind firewalls and IPS --and turtles all the way down — while the sunk costs keep getting larger. This is also why patching and pen testing are seen as central security practices— they are the flying buttresses of security architecture these days.

The lack of a proper definition and metrics has been known for a while. In part, the old Rainbow series from the NCSC (NSA) was about this. The authors realized the difficulty of defining "secure" and instead spoke of "trusted." The series established a set of features and levels of trust assurance in products to meet DOD needs. However, that was with a DOD notion of security at the time, so issues of resilience and availability (among others) weren't really addressed. That is one reason why the Rainbow Series was eventually deprecated: the commercial marketplace found it didn't apply to their needs.

Defining security principles is a hard problem, and is really in the grand challenge space for security research. It was actually stated as such 16 years ago in the CRA security Grand Challenges report (see #3). Defining accompanying metrics is not likely to be simple either, but we really need to do it or continue to come up against problems. If the only qualities we can reliably measure for systems are speed and cost, the decisions are going to be heavily weighted towards solutions that provide those at the expense of maintainability, security, reliability, and even correctness. Corporations and governments are heavily biased towards solutions that promise financial results in the next year (or next quarter) simply because that is easily measured and understood.

I've written and spoken about this topic before (see here and here for instance). But it has come to the forefront of my thinking over the last year, as I have been on sabbatical. Two recent issues have reinforced that:

  • I was cleaning up my computer storage and came across some old presentations from 10-20 years ago. With minor updating, they could be given today. Actually, I have been giving a slightly updated version of one from 11 years ago, and the audiences view it as "fresh." The theme? How we don't define or value security appropriately. (Let me know if you’d like me to present it to your group; you can also view a video of the talk given at Sandia National Laboratories,)
  • I was asked by people associated with a large entity with significant computing presence to provide some advice on cloud computing. They have been getting a strong push from management to move everything to the cloud, which they know to be a mistake, but their management is countering  their concerns about security with "it will cost less." I have heard this before from other places and given informal feedback to the parties involved. This time, I provided more organized feedback, now also available as a CERIAS tech report (here). In summary, moving to the cloud is not always the best idea, nor is it necessarily going to save money in the long term.

I hope to write some more on the issues around defining security and bucking the "conventional wisdom" once I am fully recovered from my sabbatical. There should be no shortage of material. In the meantime, I invite you to look at the cloud paper cited above and provide your comments below.