Category Archives: Security engineering

Bad security, good security, case studies, lessons learned

Internet of Bad Things

A lot of people are starting to ask about the security and privacy implications of the “Internet of Things”. Once there’s software in everything, what will go wrong? We’ve seen a botnet recruiting CCTV cameras, and a former Director of GCHQ recently told a parliamentary committee that it might be convenient if a suspect’s car could be infected with malware that would cause it to continually report its GPS position. (The new Investigatory Powers Bill will give the police and the spooks the power to hack any device they want.)

So here is the video of a talk I gave on The Internet of Bad Things to the Virus Bulletin conference. As the devices around us become smarter they will become less loyal, and it’s not just about malware (whether written by cops or by crooks). We can expect all sorts of novel business models, many of them exploitative, as well as some downright dishonesty: the recent Volkswagen scandal won’t be the last.

But dealing with pervasive malware in everything will demand new approaches. Our approach to the Internet of Bad Things includes our new Cambridge Cybercrime Centre, which will let us monitor bad things online at the kind of scale that will be required.

Efficient multivariate statistical techniques for extracting secrets from electronic devices

That’s the title of my PhD thesis, supervised by Markus Kuhn, which has become available recently as CL tech report 878:

In this thesis I provide a detailed presentation of template attacks, which are considered the most powerful kind of side-channel attacks, and I present several methods for implementing and evaluating this attack efficiently in different scenarios.

These contributions may allow evaluation labs to perform their evaluations faster, show that we can determine almost perfectly an 8-bit target value even when this value is manipulated by a single LOAD instruction (may be the best published results of this kind), and show how to cope with differences across devices, among others.

Some of the datasets used in my experiments along with MATLAB scripts for reproducing my results are available here:


Emerging, fascinating, and disruptive views of quantum mechanics

I have just spent a long weekend at Emergent Quantum Mechanics (EmQM15). This workshop is organised every couple of years by Gerhard Groessing and is the go-to place if you’re interested in whether quantum mechanics dooms us to a universe (or multiverse) that can be causal or local but not both, or whether we might just make sense of it after all. It’s held in Austria – the home not just of the main experimentalists working to close loopholes in the Bell tests, such as Anton Zeilinger, but of many of the physicists still looking for an underlying classical model from which quantum phenomena might emerge. The relevance to the LBT audience is that the security proofs of quantum cryptography, and the prospects for quantum computing, turn on this obscure area of science.

The two themes emergent from this year’s workshop are both relevant to these questions; they are weak measurement and emergent global correlation.

Weak measurement goes back to the 1980s and the thesis of Lev Vaidman. The idea is that you can probe the trajectory of a quantum mechanical particle by making many measurements of a weakly coupled observable between preselection and postselection operations. This has profound theoretical implications, as it means that the Heisenberg uncertainty limit can be stretched in carefully chosen circumstances; Masanao Ozawa has come up with a more rigorous version of the Heisenberg bound, and in fact gave one of the keynote talks two years ago. Now all of a sudden there are dozens of papers on weak measurement, exploring all sorts of scientific puzzles. This leads naturally to the question of whether weak measurement is any good for breaking quantum cryptosystems. After some discussion with Lev I’m convinced the answer is almost certainly no; getting information about quantum states takes exponentially much work and lots of averaging, and works only in specific circumstances, so it’s easy for the designer to forestall. There is however a question around interdisciplinary proofs. Physicists have known about weak measurement since 1988 (even if few paid attention till a few years ago), yet no-one has rushed to tell the crypto community “Sorry, guys, when we said that nothing can break the Heisenberg bound, we kinda overlooked something.”

The second theme, emergent global correlation, may be of much more profound interest, to cryptographers and physicists alike.

Continue reading Emerging, fascinating, and disruptive views of quantum mechanics

CHERI: Architectural support for the scalable implementation of the principle of least privilege

[CHERI tablet photo]
FPGA-based CHERI prototype tablet — a 64-bit RISC processor that boots CheriBSD, a CHERI-enhanced version of the FreeBSD operating system.
Only slightly overdue, this post is about our recent IEEE Security and Privacy 2015 paper, CHERI: A Hybrid Capability-System Architecture for Scalable Software Compartmentalization. We’ve previously written about how our CHERI processor blends a conventional RISC ISA and processor pipeline design with a capability-system model to provide fine-grained memory protection within virtual address spaces (ISCA 2014, ASPLOS 2015). In our this new paper, we explore how CHERI’s capability-system features can be used to implement fine-grained and scalable application compartmentalisation: many (many) sandboxes within a single UNIX process — a far more efficient and programmer-friendly target for secure software than current architectures.

Continue reading CHERI: Architectural support for the scalable implementation of the principle of least privilege

Four cool new jobs

We’re advertising for four people to join the security group from October.

The first three are for two software engineers to join our new cybercrime centre, to develop new ways of finding bad guys in the terabytes and (soon) petabytes of data we get on spam, phish and other bad stuff online; and a lawyer to explore and define the boundaries of how we share cybercrime data.

The fourth is in Security analysis of semiconductor memory. Could you help us come up with neat new ways of hacking chips? We’ve invented quite a few of these in the past, ranging from optical fault induction through semi-invasive attacks generally. What’s next?

Double bill: Password Hashing Competition + KeyboardPrivacy

Two interesting items from Per Thorsheim, founder of the PasswordsCon conference that we’re hosting here in Cambridge this December (you still have one month to submit papers, BTW).

First, the Password Hashing Competition “have selected Argon2 as a basis for the final PHC winner”, which will be “finalized by end of Q3 2015”. This is about selecting a new password hashing scheme to improve on the state of the art and make brute force password cracking harder. Hopefully we’ll have some good presentations about this topic at the conference.

Second, and unrelated: Per Thorsheim and Paul Moore have launched a privacy-protecting Chrome plugin called Keyboard Privacy to guard your anonymity against websites that look at keystroke dynamics to identify users. So, you might go through Tor, but the site recognizes you by your typing pattern and builds a typing profile that “can be used to identify you at other sites you’re using, were identifiable information is available about you”. Their plugin intercepts your keystrokes, batches them up and delivers them to the website at a constant pace, interfering with the site’s ability to build a profile that identifies you.

Crypto Wars 2.0

Today we unveil a major report on whether law enforcement and intelligence agencies should have exceptional access to cryptographic keys and to our computer and communications data generally. David Cameron has called for this, as have US law enforcement leaders such as FBI Director James Comey.

This policy repeats a mistake of the 1990s. The Clinton administration tried for years to seize control of civilian cryptography, first with the Clipper Chip, and then with various proposals for ‘key escrow’ or ‘trusted third party encryption’. Back then, a group of experts on cryptography and computer security got together to explain why this was a bad idea. We have now reconvened in response to the attempt by Cameron and Comey to resuscitate the old dead horse of the 1990s.

Our report, Keys Under Doormats: Mandating insecurity by requiring government access to all data and communications, is timed to set the stage for a Wednesday hearing of the Senate Judiciary Committee at which Mr Comey will present his proposals. The reply to Comey will come from Peter Swire, who was on the other side twenty years ago (he was a Clinton staffer) and has written a briefing on the first crypto war here. Peter was recently on President Obama’s NSA review group. He argues that the real way to fix the problems complained of is to fix the mutual legal assistance process – which is also my own view.

Our report is also highly relevant to the new ‘Snoopers’ Charter’ that Home Secretary Teresa May has promised to put before parliament this fall. Mrs May has made clear she wants access to everything.

However this is both wrong in principle, and unworkable in practice. Building back doors into all computer and communication systems is against most of the principles of security engineering, and it also against the principles of human rights. Our right to privacy, set out in section 8 of the European Convention on Human Rights, can only be overridden by mechanisms that meet three tests. First, they must be set out in law, with sufficient clarity for their effects to be foreseeable; second, they must be proportionate; third, they must be necessary in a democratic society. As our report makes clear, universal exceptional access will fail all these tests by a mile.

For more, see the New York Times.

Phishing that looks like another risk altogether

I came across an unusual DHL branded phish recently…

The user receives an email with the Subject of “DHL delivery to [ xxx ]June ©2015” where xxx is their valid email address. The From is forged as “DHLexpress<>” (the criminal will have used this domain since hasn’t yet adopted DMARC whereas has a p=reject policy which would have prevented this type of forgery altogether).

The email looks like this (I’ve blacked out the valid email address):
DHL email body
and so, although we would all wish otherwise, it is predictable that many recipients will have opened the attachment.

BTW: if the image looks in the least bit fuzzy in your browser then click on the image to see the full-size PNG file and appreciate how realistic the email looks.

I expect many now expect me to explain about some complex 0-day within the PDF that infects the machine with malware, because after all, that’s the main risk from opening unexpected attachments isn’t it ?

But no!
Continue reading Phishing that looks like another risk altogether

Which Malware Lures Work Best?

Last week at the APWG eCrime Conference in Barcelona I presented some new results about an old Instant Messaging (IM) worm from a paper written by Tyler Moore and myself.

In late April 2010 users of the Yahoo and Microsoft IM systems started to get messages from their buddies which said, for example:
foto ☺
where the email address was theirs and the URL was for some malware.

Naturally, since the message was from their buddy a lot of folks clicked on the link and when the Windows warning pop-up said “you cannot see this photo until you press OK” they pressed OK and (since the Windows message was in fact a warning about executing unknown programs downloaded from the Internet) they too became infected with the malware. Hence they sent foto ☺ messages to all their buddies and the worm spread at increasing speed.

By late May 2010 I had determined how the malware was controlled (it resolved hostnames to locate IRC servers then joined particular channels where the topic was the message to be sent to buddies) and built a Perl program to join in and monitor what was going on. I also determined that the criminals were often hosting their malware on hosting sites with world-readable Apache weblogs so we could get exact counts of malware downloads (how many people clicked on the links).

Full details, and the story of a number of related worms that spread over the next two years can be found in the academic paper (and are summarised in the slides I used for a very short talk in Barcelona and a longer version I presented a week earlier in Luxembourg).

The key results are:

  • Thanks to some sloppiness by the criminals we had some brief snapshots of activity from an IRC channel used when the spreading phase was complete and infected machines were being forced to download new malware — this showed that 95% of people had clicked OK to dismiss the Microsoft warning message.
  • We had sufficient download data to estimate that around 3 million users were infected by the initial worm and we have records of over 14 million distinct downloads over all of the different worms (having ignored events caused by security monitoring, multiple clicks by the same user, etc.). That is — this was a large scale event.
  • We were able to compare the number of clicks during periods where the criminals vacillated between using URL shorteners in their URLs and when they used hostnames that (vaguely resembled) brands such as Facebook, MySpace, Orkut and so on. We found that when shorteners were used this reduced the number of clicks by almost half — presumably because it made users more cautious.
  • From early 2011 the worms were mainly affecting Brazil — and the simple “foto ☺” had long been replaced by other textual lures. We found that when the criminals used lures in Portuguese (e.g. “eu acho que é você na”, which has, I was told in Barcelona, a distinctive Brazilian feel to it) they were far more successful in getting people to click than when they used ‘language independent’ lures such as “hahha foto”

There’s nothing here which is super-surprising, but it is useful to see our preconceptions borne out not in a laboratory experiment (where it is hard to ensure that the experimental subjects are behaving quite the way that they would ‘in the wild’) but by large scale measurements from real events.

Thinking of selling your old phone? Watch out!

Today we unveil two papers describing serious and widespread vulnerabilities in Android mobile phones. The first presents a Security Analysis of Factory Resets. Now that hundreds of millions of people buy and sell smartphones secondhand and use them for everything from banking to dating, it’s important to able to sanitize your phone. You need to clean it when you buy it, so you don’t get caught by malware; and even more when you sell it, so you don’t give away your bank credentials or other personal information. So does the factory reset function actually work? We bought a couple of dozen second-hand Android phones and tested them to find out.

The news is not at all good. We were able to retrieve the Google master cookie from the great majority of phones, which means that we could have logged on to the previous owner’s gmail account. The reasons for failure are complex; new phones are generally better than old ones, and Google’s own brand phones are better than the OEM offerings. However the vendors need to do a fair bit of work, and users need to take a fair amount of care.

Attacks on a sold phone that could not be properly sanitized are one example of what we call a “user-not-present” attack. Another is when your phone is stolen. Many security software vendors offer a facility to lock or wipe your phone remotely when this happens, and it’s a standard feature with mobile antivirus products. Do these ‘solutions’ work?

You guessed it. Antivirus software that relies on a faulty factory reset can only go so far, and there’s only so much you can do with a user process. The AV vendors have struggled with a number of design tradeoffs, but the results are not that impressive. See Security Analysis of Consumer-Grade Anti-Theft Solutions Provided by Android Mobile Anti-Virus Apps for the gory details. These failings mean that staff at firms which handle lots of second-hand phones (whether lost, stolen, sold or given to charity) could launch some truly industrial-scale attacks. These papers appear today at the Mobile Security Technology workshop at IEEE Security and Privacy.