Category Archives: Security engineering

Bad security, good security, case studies, lessons learned

Offender tagging 2.0

Academic papers, Legal issues, News coverage, Security engineering

Three of our clients have been acquitted of tampering with curfew tags after the Ministry of Justice and G4S were unwilling to have an independent forensic team examine their evidence. This brings to five the number of tag-tampering prosecutions that have been withdrawn or collapsed when the defence says “Right, prove it then.” I reported the first case here.

The three latest matters were high-profile terrorism cases, involving three of the nine men tagged under the new Terrorism Prevention and Investigation Measure (TPIM) – a kind of national-security ASBO handed out by MI5, and which had already been criticised by David Anderson QC, the government’s independent reviewer of terrorism legislation, for low standards of proof. Unlike a normal ASBO which a court gives “on the balance of probabilities”, you can get a TPIM if the Home Secretary declares she has a “reasonable suspicion”.

The Ministry of Justice should perhaps, when they let the tagging contracts, have read our 1994 paper on the John Munden case, or the post here about the similar case of Jane Badger. If you’re designing a system one of whose functions is to provide evidence, you’d better design it to withstand hostile review. “Trust us” doesn’t cut it in criminal trials, and neither does “I’m afraid that’s commercially confidential.”

We're hiring again

Security economics, Security engineering, Security psychology, Spam, Web security

We have a vacancy for a postdoc to work on the economics of cybercrime for two years from January. It might suit someone with a PhD in economics or criminology and an interest in online crime; or a PhD in computer science with an interest in security and economics.

Security economics has grown rapidly in the last decade; security in global systems is usually an equilibrium that emerges from the selfish actions of many independent actors, and security failures often follow from perverse incentives. To understand better what works and what doesn’t, we need both theoretical models and empirical data. We have access to various large-scale sources of data relating to cybercrime – email spam, malware samples, DNS traffic, phishing URL feeds – and some or all of this data could be used in this research. We’re very open-minded about what work might be done on this project; possible topics include victim analysis, malware analysis, spam data mining, data visualisation, measuring attacks, how security scales (or fails to), and how cybercrime data could be shared better.

This is an international project involving colleagues at CMU, SMU and the NCFTA.

Google funding of open-source security projects

Open-source security, Operating systems, Security engineering

I was pleased to contribute to a recent blog article by Ben Laurie, a frequent collaborator with the Cambridge security group, on the Google Open Source Programs Office blog. We describe open-source security work OSPO has sponsored over the last couple of years, including our joint work on Capsicum, and its followup projects funded jointly by Google and the FreeBSD Foundation. He also talks about Google support for Certificate Transparency, OpenSSL, Tor, and Libpurple — projects focussed not just on communications security, but also communications privacy on the Internet.

Capsicum

Over the last decade or so, it has become increasingly (and painfully) apparent that ACLs and MAC, which were originally designed to protect expensive mainframes from their users, and the users from each other, are failing to secure modern cheap machines with single users who need protecting from the software they run.

Instead, we need fine-grained access control and strong sandboxing.
Continue reading Google funding of open-source security projects →

Offender tagging

Hardware & signals, Legal issues, News coverage, Politics, Usability

August was a slow month, but we got a legal case where our client was accused of tampering with a curfew tag, and I was asked for an expert report on the evidence presented by Serco, the curfew tagging contractor. Many offenders in the UK are released early (or escape prison altogether) on condition that they stay at home from 8pm to 8am and wear an ankle bracelet so their compliance can be monitored. These curfew tags have been used for fourteen years now but are controversial for various reasons; but with the prisons full and 17,500 people on tag at any one time, the objective of policy is to improve the system rather than abolish it.

In this spirit I offer a redacted version of my expert report which may give some insight into the frailty of the system. The logs relating to my defendant’s case showed large numbers of false alarms; some of these had good explanations (such as power cuts) but many didn’t. The overall impression is of an unreliable technology surrounded by chaotic procedures. Of policy concern too is that the tagging contractor not only supplies the tags and the back-end systems, but the call centre and the interface to the court system. What’s more, if you break your curfew, it isn’t the Crown Prosecution Service that takes you before the magistrates, but the contractor – relying on expert evidence from one of its subcontractors. Such closed systems are notoriously vulnerable to groupthink. Anyway, we asked the court for access not just to the tag in the case, but a complete set of tagging equipment for testing, plus system specifications, false alarm statistics and audit reports. The contractor promptly replied that “although we continue to feel that the defendant is in breach of the order, our attention has been drawn to a number of factors that would allow me to properly discontinue proceedings in the public interest.”

The report is published with the consent of my client and her solicitor. Long-time readers of this blog may recall similarities with the case of Jane Badger. If you’re designing systems on whose output someone may have to rely in court, you’d better think hard about how they’ll stand up to hostile review.

Eavesdropping a fax machine

Hardware & signals, News coverage

I was intrigued this morning to see on the front page of the Guardian newspaper a new revelation by NSA whistleblower Edward Snowden: a US eavesdropping technique “DROPMIRE implanted on the Cryptofax at the EU embassy [Washington] D.C.”. I was even more intrigued by an image that accompanied the report (click for higher resolution):

The Guardian, 1 July 2013, page 1

Having done many experiments to eavesdrop on office equipment myself, the noisy image at the bottom third of the picture above looked instantly familiar: it is what you might get from listening with a radio receiver on the compromising emanations of a video signal of a page of text. Continue reading Eavesdropping a fax machine →

Security and Human Behaviour 2013

Academic papers, Politics, Security economics, Security psychology, Social networks, Usability

I’m liveblogging the Workshop on Security and Human Behaviour which is being held at USC in Los Angeles. The participants’ papers are here; for background, see the liveblogs for SHB 2008-12 which are linked here and here. Blog posts summarising the talks at the workshop sessions will appear as followups below. (Added: there is another liveblog by Vaibhav Garg.)

A further observation on quantum computing

Academic papers, Security engineering

Today we’ve published a paper showing that Bell’s inequality is violated in fluid mechanics. What has this to do with computing or security? Well, when we posted a paper back in February pointing out that hydrodynamic models of quantum physics raise questions about the scalability of quantum computing, a number of people asked for a better explanation of how this squares with the Bell tests. John Bell proved an inequality in 1964 that applies to classical particles but that is broken by quantum mechanical ones. In today’s paper we show that Bell’s inequality does not hold in classical fluid dynamics, as angular momentum and energy are delocalised in the fluid.

This may have implications for engineering, science and philosophy. On the engineering front, nine-figure sums have been poured into developing quantum computers, but even advocates of quantum computing admit they don’t really work. As our February paper argued, a hydrodynamic interpretation of quantum mechanics may suggest reasons why.

On the scientific front, the Bell tests are commonly seen as excluding not just local hidden-variable models of quantum mechanics, but local realism too. Our paper shows that the two are distinct, and thus leaves more room for research on quantum foundations. It also shows that we should be more careful in our use of terms such as ‘local’ – which might be of interest to the philosophers; the Bell tests do not draw quite as clear a dividing line between the quantum and classical worlds as many have believed.

Revisiting secure introduction via hyperlinks

Academic papers, Protocols, Security engineering, Web security

Today at W2SP I presented a new paper making the case for distributing security policy in hyperlinks. The basic idea is old, but I think the time is right to re-examine it. After the DigiNotar debacle, the community is getting serious about fixing PKI on the web. It was hot topic at this week’s IEEE Security & Privacy (Oakland), highlighted by Jeremy Clark and Paul van Oorschot’s excellent survey paper. There are a slew of protocols under development like key pinning (HPKP), Certificate Transparency, TACK, and others. To these I add s-links, a complementary mechanism to declare support for new proposals in HTML links. Continue reading Revisiting secure introduction via hyperlinks →

A search engine for code

Academic papers, Security engineering, Seminars, Useful software

In a seminar today, we will unveil Rendezvous, a search engine for code. Built by Wei-Ming Khoo, it will analyse an unknown binary, parse it into functions, index them, and compare them with a library of code harvested from open-source projects.

As time goes on, the programs we need to reverse engineer get ever larger, so we need better tools. Yet most code nowadays is not written from scratch, but cut and pasted. Programmers are not an order of magnitude more efficient than a generation ago; it’s just that we have more and better libraries to draw on nowadays, and a growing shared heritage of open software. So our idea is to reframe the decompilation problem as a search problem, and harness search-engine technology to the task.

As with a text search engine, Rendezvous uses a number of different techniques to index a target binary, some of which are described in this paper, along with the main engineering problems. As well as reverse engineering suspicious binaries, code search engines could be used for many other purposes such as monitoring GPL compliance, plagiarism detection, and quality control. On the dark side, code search can be used to find new instances of disclosed vulnerabilities. Every responsible software vendor or security auditor should build one. If you’re curious, here is the demo.