Category Archives: Security engineering

Bad security, good security, case studies, lessons learned

Job ad: post-doctoral researcher in security, operating systems, computer architecture

Jobs, Operating systems, Processors, Programming languages

We are pleased to announce a job opening at the University of Cambridge Computer Laboratory for a post-doctoral researcher working in the areas of security, operating systems, and computer architecture.

Research Associate in compiler-assisted instrumentation of operating system kernels
University of Cambridge – Faculty of Computer Science and Technology
Salary: £27,578-£35,938 pa

The funds for this post are available for up to two years:

We are seeking a Post-doctoral Research Associate to join the CTSRD and MRC2 projects, which are investigating fundamental revisions to CPU architecture, operating system (OS), programming language, and networking structures in support of computer security. The two projects are collaborations between the University of Cambridge and SRI International, and part of the DARPA CRASH and MRC research programmes on clean-slate computer system design.

This position will be an integral part of an international team of researchers spanning multiple institutions across academia and industry. The successful candidate will contribute to low-level aspects of system software: compilers, language run-times, and OS kernels. Responsibilities will include researching the application of novel dynamic instrumentation techniques to C-language operating systems and applications, including adaptation of the FreeBSD kernel and LLVM compiler suite, and evaluation of the resulting system.

Continue reading Job ad: post-doctoral researcher in security, operating systems, computer architecture →

Some evidence on multi-word passphrases

Academic papers, Authentication, Security engineering, Security psychology, Usability, Web security

Using a multi-word “passphrase” instead of a password has been suggested for decades as a way to thwart guessing attacks. The idea is now making a comeback, for example with the Fastwords proposal which identifies that mobile phones are optimised for entering dictionary words and not random character strings. Google’s recent password advice suggests condensing a sentence to form a password, while Komanduri et al.’s recent lab study suggests simply requiring longer passwords may be the best security policy. Even xkcd espouses multi-word passwords (albeit with randomly-chosen words). I’ve been advocating through my research though that authentication schemes can only be evaluated by studying large user-chosens distribution in the wild and not the theoretical space of choices. There’s no public data on how people choose passphrases, though Kuo et al.’s 2006 study for mnemonic-phrase passwords found many weak choices. In my recent paper (written with Ekaterina Shutova) presented at USEC last Friday (a workshop co-located with Financial Crypto), we study the problem using data crawled from the now-defunct Amazon PayPhrase system, introduced last year for US users only. Our goal wasn’t to evaluate the security of the scheme as deployed by Amazon, but learn more how people choose passphrases in general. While this is a relatively limited data source, our results suggest some caution on this approach. Continue reading Some evidence on multi-word passphrases →

Three-paper Thursday: capability systems

Operating systems, Processors, Programming languages, Three Paper Thursday

This week, my contribution to our three-paper Thursday research reading list series is on capability systems. Capabilities are unforgeable tokens of authority — capability systems are hardware, operating, or programming systems in which access to resources can occur only using capabilities. Capability system research in the 1970s motivated many fundamental insights into practical articulations of the principle of least privilege, separation of mechanism and policy, and the interactions between program representation and security. They also formed the intellectual foundation for a recent renaissance in capability-oriented microkernels (L4, sel4) and programming languages (Joe-E, Caja, ECMAScript 5). Capability systems have a long history at Cambridge, including the CAP Computer, and more recently, our work on Capsicum: practical capabilities for UNIX. I’ve selected three “must read” papers, but there are plenty of other influential pieces that, unfortunately, space doesn’t allow for!
Continue reading Three-paper Thursday: capability systems →

Social authentication – harder than it looks!

Academic papers, News coverage, Privacy technology, Security economics, Security psychology, Usability

This is the title of a paper we’ll be presenting next week at the Financial Crypto conference (slides). There is also coverage in the New Scientist.

Facebook has a social authentication mechanism where you may be asked to recognise some of your friends from photos as part of the login process. We analysed this and found it to be vulnerable to guessing by your friends, and also to modern face-recognition systems. Most people want privacy only from those close to them; if you’re having an affair then you want your partner to not find out but you don’t care if someone in Mongolia learns about it. And if your partner finds out and becomes your ex, then you don’t want them to be able to cause havoc on your account. Celebrities are similar, except that everyone is their friend (and potentially their enemy).

Second, if someone outside your circle of friends is doing a targeted attack on you, then by friending your friends they can get some access to your social circle to collect photos, which they might use in image-recognition software or even manually to pass the test.
Continue reading Social authentication – harder than it looks! →

How hard are PINs to guess?

Academic papers, Authentication, Banking security, Usability

Note: this research was also blogged today at the NY Times’ Bits technology blog.

I’ve personally been researching password statistics for a few years now (as well as personal knowledge questions) and our research group has a long history of research on banking security. In an upcoming paper at next weel’s Financial Cryptography conference written with Sören Preibusch and Ross Anderson, we’ve brought the two research threads together with the first-ever quantitative analysis of the difficulty of guessing 4-digit banking PINs. Somewhat amazingly given the importance of PINs and their entrenchment in infrastructure around the world, there’s never been an academic study of how people actually choose them. After modeling banking PIN selection using a combination of leaked data from non-banking sources and a massive online survey, we found that people are significantly more careful choosing PINs then online passwords, with a majority using an effectively random sequence of digits. Still, the persistence of a few weak choices and birthdates in particular suggests that guessing attacks may be worthwhile for an opportunistic thief. Continue reading How hard are PINs to guess? →

Cloudy with a Chance of Privacy

Privacy technology, Protocols, Social networks, Three Paper Thursday, Usability

Three Paper Thursday is an experimental new feature in which we highlight research that group members find interesting.

When new technologies become popular, we privacy people are sometimes miffed that nobody asked for our opinions during the design phase. Sometimes this leads us to make sweeping generalisations such as “only use the Cloud for things you don’t care about protecting” or “Facebook is only for people who don’t care about privacy.” We have long accused others of assuming that the real world is incompatible with privacy, but are we guilty of assuming the converse?

On this Three Paper Thursday, I’d like to highlight three short papers that challenge these zero-sum assumptions. Each is eight pages long and none requires a degree in mathematics to understand; I hope you enjoy them.

Continue reading Cloudy with a Chance of Privacy →

Observations from two weeks of SSH brute force attacks

Authentication, Protocols

Earlier this month, I blogged about monitoring password-guessing attacks on a server, via a patched OpenSSH. This experiment has now been running for just over two weeks, and there are some interesting results. I’ve been tweeting these since the start.

As expected, the vast majority of password-guessing attempts are quite dull, and fall into one of two categories. Firstly there are attempts with a large number of ‘poor’ passwords (e.g. “password”, “1234”, etc…) against a small number of accounts which are very likely to exist (almost always “root”, but sometimes others such as “bin”).

Secondly, there were attempts on a large number of accounts which might plausibly exist (e.g. common first names and software packages such as ‘oracle’). For these, there were a very small number of password attempts, normally only trying the username as password. Well established good practices such as choosing a reasonably strong password and denying password-based log-in to the root account will be effective against both categories of attacks. Surprisingly, there were few attempts which were obviously default passwords from software packages (but they perhaps were hidden in the attempts where username equalled password). However, one attempt was username: “rfmngr”, password: “$rfmngr$”, which is the default password for Websense RiskFilter (see p.10 of the manual).

There were, however, some more interesting attempts. Continue reading Observations from two weeks of SSH brute force attacks →

Metrics for dynamic networks

Academic papers, Security engineering, Social networks

There’s a huge literature on the properties of static or slowly-changing social networks, such as the pattern of friends on Facebook, but almost nothing on networks that change rapidly. But many networks of real interest are highly dynamic. Think of the patterns of human contact that can spread infectious disease; you might be breathed on by a hundred people a day in meetings, on public transport and even in the street. Yet if we were facing a flu pandemic, how could we measure whether the greatest spreading risk came from high-order static nodes, or from dynamic ones? Should we close the schools, or the Tube?

Today we unveiled a paper which proposes new metrics for centrality in dynamic networks. We wondered how we might measure networks where mobility is of the essence, such as the spread of plague in a medieval society where most people stay in their villages and infection is carried between them by a small number of merchants. We found we can model the effects of mobility on interaction by embedding a dynamic network in a larger time-ordered graph to which we can apply standard graph theory tools. This leads to dynamic definitions of centrality that extend the static definitions in a natural way and yet give us a much better handle on things than aggregate statistics can. I spoke about this work today at a local workshop on social networking, and the paper’s been accepted for Physical Review E. It’s joint work with Hyoungshick Kim.

Job ad: post-doctoral researcher in security, operating systems, computer architecture

Hardware & signals, Jobs, Operating systems, Processors

We are pleased to announce a job opening at the University of Cambridge Computer Laboratory for a post-doctoral researcher working in the areas of security, operating systems, and computer architecture.

Research Associate
University of Cambridge – Faculty of Computer Science & Technology

Salary: £27,428 – £35,788 pa
The funds for this post are available for one year:

We are seeking a Post-doctoral Research Associate to join the CTSRD Project, which is investigating fundamental improvements to CPU architecture, operating system (OS), and programming language structure in support of computer security. The CTSRD Project is a collaboration between the University of Cambridge and SRI International, and part of the DARPA CRASH research programme on clean-slate computer system design.

This position will be an integral part of an international team of researchers spanning multiple institutions across academia and industry. The successful candidate will contribute to low-level aspects of system software: compilers, language run-times, and OS kernels. Responsibilities will include researching the application of novel dynamic techniques to C-language operating systems and applications, including adaptation of the FreeBSD kernel and LLVM compiler suite, and measurement of the resulting system.

An ideal candidate will hold (or be close to finishing) a PhD in Computer Science, Mathematics, or similar with a strong background in low-level system software development, which should include at least of one of strong kernel development experience (FreeBSD preferred; Linux acceptable), or compiler internals experience (LLVM preferred; gcc acceptable). Strong experience with the C programming language is critical. Some background in computer security is also recommended.

Candidates must be able to provide evidence of relevant work demonstrated by a research publication track record or industrial experience. Good interpersonal and organisational skills and the ability to work in a team are also essential. This post is intended to be filled as soon as practically possible after the closing date.

Applications should include:

  • Curriculum Vitae
  • Brief statement of the particular contribution you would make to the project
  • A completed form CHRIS6

Completed applications should be sent by post to: Personnel-Admin,Computer Laboratory, William Gates Building, JJ Thomson Avenue, Cambridge, CB3 0FD, or by email to: personnel-admin@cl.cam.ac.uk

Quote Reference: NR10692
Closing Date: 10 January 2012

The University values diversity and is committed to equality of opportunity.

Privacy event on Wednesday

Legal issues, News coverage, Politics, Privacy technology, Security economics, Security engineering

I will be talking in London on Wednesday at a workshop on Anonymity, Privacy, and Open Data about the difficulty of anonymising medical records properly. I’ll be on a panel with Kieron O’Hara who wrote a report on open data for the Cabinet Office earlier this year, and a spokesman from the ICO.

This will be the first public event on the technology and policy issues surrounding anonymisation since yesterday’s announcement that the government will give wide access to anonymous versions of our medical records. I’ve written extensively on the subject: for an overview, see my book chapter which explores the security of medical systems in general from p 282 and the particular problems of using “anonymous” records in research from p 298. For the full Monty, start here.

Anonymity is hard enough if the data controller is capable, and motivated to try hard. In the case of the NHS, anonymity has always been perfunctory; the default is to remove patient names and addresses but leave their postcodes and dates of birth. This makes it easy to re-identify about 99% of patients (the exceptions are mostly twins, soldiers, students and prisoners). And since I wrote that book chapter, the predicted problems have come to pass; for example the NHS lost a laptop containing over eight million patients’ records.