Category Archives: Politics

Text mining is harder than you think

Academic papers, Internet censorship, Legal issues, News coverage, Politics, Security engineering

Following last year’s row about Apple’s proposal to scan all the photos on your iPhone camera roll, EU Commissioner Johansson proposed a child sex abuse regulation that would compel providers of end-to-end encrypted messaging services to scan all messages in the client, and not just for historical abuse images but for new abuse images and for text messages containing evidence of grooming.

Now that journalists are distracted by the imminent downfall of our great leader, the Home Office seems to think this is a good time to propose some amendments to the Online Safety Bill that will have a similar effect. And while the EU planned to win the argument against the pedophiles first and then expand the scope to terrorist radicalisation and recruitment too, Priti Patel goes for the terrorists from day one. There’s some press coverage in the Guardian and the BBC.

We explained last year why client-side scanning is a bad idea. However, the shift of focus from historical abuse images to text scanning makes the government story even less plausible.

Detecting online wickedness from text messages alone is hard. Since 2016, we have collected over 99m messages from cybercrime forums and over 49m from extremist forums, and these corpora are used by 179 licensees in 55 groups from 42 universities in 18 countries worldwide. Detecting hate speech is a good proxy for terrorist radicalisation. In 2018, we thought we could detect hate speech with a precision of typically 92%, which would mean a false-alarm rate of 8%. But the more complex models of 2022, based on Google’s BERT, when tested on the better collections we have now, don’t do significantly better; indeed, now that we understand the problem in more detail, they often do worse. Do read that paper if you want to understand why hate-speech detection is an interesting scientific problem. With some specific kinds of hate speech it’s even harder; an example is anti-semitism, thanks to the large number of synonyms for Jewish people. So if we were to scan 10bn messages a day in Europe there would be maybe a billion false alarms for Europol to look at.

We’ve been scanning the Internet for wickedness for over fifteen years now, and looking at various kinds of filters for everything from spam to malware. Filtering requires very low false positive rates to be feasible at Internet scale, which means either looking for very specific things (such as indicators of compromise by a specific piece of malware) or by having rich metadata (such as a big spam run from some IP address space you know to be compromised). Whatever filtering Facebook can do on Messenger given its rich social context, there will be much less that a WhatsApp client can do by scanning each text on its way through.

So if you really wish to believe that either the EU’s CSA Regulation or the UK’s Online Harms Bill is an honest attempt to protect kids or catch terrorists, good luck.

European Commission prefers breaking privacy to protecting kids

Academic papers, Internet censorship, Legal issues, News coverage, Politics, Security economics

Today, May 11, EU Commissioner Ylva Johannson announced a new law to combat online child sex abuse. This has an overt purpose, and a covert purpose.

The overt purpose is to pressure tech companies to take down illegal material, and material that might possibly be illegal, more quickly. A new agency is to be set up in the Hague, modeled on and linked to Europol, to maintain an official database of illegal child sex-abuse images. National authorities will report abuse to this new agency, which will then require hosting providers and others to take suspect material down. The new law goes into great detail about the design of the takedown process, the forms to be used, and the redress that content providers will have if innocuous material is taken down by mistake. There are similar provisions for blocking URLs; censorship orders can be issued to ISPs in Member States.

The first problem is that this approach does not work. In our 2016 paper, Taking Down Websites to Prevent Crime, we analysed the takedown industry and found that private firms are much better at taking down websites than the police. We found that the specialist contractors who take down phishing websites for banks would typically take six hours to remove an offending website, while the Internet Watch Foundation – which has a legal monopoly on taking down child-abuse material in the UK – would often take six weeks.

We have a reasonably good understanding of why this is the case. Taking down websites means interacting with a great variety of registrars and hosting companies worldwide, and they have different ways of working. One firm expects an encrypted email; another wants you to open a ticket; yet another needs you to phone their call centre during Peking business hours and speak Mandarin. The specialist contractors have figured all this out, and have got good at it. However, police forces want to use their own forms, and expect everyone to follow police procedure. Once you’re outside your jurisdiction, this doesn’t work. Police forces also focus on process more than outcome; they have difficulty hiring and retaining staff to do detailed technical clerical work; and they’re not much good at dealing with foreigners.

Our takedown work was funded by the Home Office, and we recommended that they run a randomised controlled trial where they order a subset of UK police forces to use specialist contractors to take down criminal websites. We’re still waiting, six years later. And there’s nothing in UK law that would stop them running such a trial, or that would stop a Chief Constable outsourcing the work.

So it’s really stupid for the European Commission to mandate centralised takedown by a police agency for the whole of Europe. This will be make everything really hard to fix once they find out that it doesn’t work, and it becomes obvious that child abuse websites stay up longer, causing real harm.

Oh, and the covert purpose? That is to enable the new agency to undermine end-to-end encryption by mandating client-side scanning. This is not evident on the face of the bill but is evident in the impact assessment, which praises Apple’s 2021 proposal. Colleagues and I already wrote about that in detail, so I will not repeat the arguments here. I will merely note that Europol coordinates the exploitation of communications systems by law enforcement agencies, and the Dutch National High-Tech Crime Unit has developed world-class skills at exploiting mobile phones and chat services. The most recent case of continent-wide bulk interception was EncroChat; although reporting restrictions prevent me telling the story of that, there have been multiple similar cases in recent years.

So there we have it: an attack on cryptography, designed to circumvent EU laws against bulk surveillance by using a populist appeal to child protection, appears likely to harm children instead.

A striking memoir by Gus Simmons

Authentication, News coverage, Politics

Gus Simmons is one of the pioneers of cryptography and computer security. His contributions to public-key cryptography, unconditional authentication, covert channels and information hiding earned him an honorary degree, fellowship of the IACR, and election to the Rothschild chair of mathematics when he visited us in Cambridge in 1996. And this was his hobby; his day job was a mathematician at Sandia National Laboratories, where he worked on satellite imagery, arms-control treaty verification, and the command and control of nuclear weapons.

During lockdown, Gus wrote a book of stories about growing up in West Virginia during the depression years of the 1930s. After he circulated it privately to a few friends in the cryptographic community, we persuaded him to put it online so everyone can read it. During this desolate time, coal mines closed and fired their workers, who took over abandoned farms and survived as best they could. Gus’s memoir is a gripping oral history of a period when some parts of the U.S.A. were just as poor as rural Africa today.

Here it is: Another Time, Another Place, Another Story.

WEIS 2022 call for papers

Call for papers, Cybercrime, Politics, Security economics, Security psychology

The 2022 Workshop on the Economics of Information Security will be held at Tulsa, Oklahoma, on 21-22 June 2022. Paper submissions are due by 28 February 2022. After two virtual events we’re eager to get back to meeting in person if we possibly can.

The program chairs for 2022 are Sadia Afroz and Laura Brandimarte, and here is the call for papers.

We originally set this as 20-21, being unaware that June 20 is the Juneteenth holiday in the USA. Sorry about that.

Anyway, we hope to see lots of you in Tulsa!

Bugs in our pockets?

Academic papers, Internet censorship, Legal issues, News coverage, Operating systems, Politics, Privacy technology, Security economics, Security psychology

In August, Apple announced a system to check all our iPhones for illegal images, then delayed its launch after widespread pushback. Yet some governments continue to press for just such a surveillance system, and the EU is due to announce a new child protection law at the start of December.

Now, in Bugs in our Pockets: The Risks of Client-Side Scanning, colleagues and I take a long hard look at the options for mass surveillance via software embedded in people’s devices, as opposed to the current practice of monitoring our communications. Client-side scanning, as the agencies’ new wet dream is called, has a range of possible missions. While Apple and the FBI talked about finding still images of sex abuse, the EU was talking last year about videos and text too, and of targeting terrorism once the argument had been won on child protection. It can also use a number of possible technologies; in addition to the perceptual hash functions in the Apple proposal, there’s talk of machine-learning models. And, as a leaked EU internal report made clear, the preferred outcome for governments may be a mix of client-side and server-side scanning.

In our report, we provide a detailed analysis of scanning capabilities at both the client and the server, the trade-offs between false positives and false negatives, and the side effects – such as the ways in which adding scanning systems to citizens’ devices will open them up to new types of attack.

We did not set out to praise Apple’s proposal, but we ended up concluding that it was probably about the best that could be done. Even so, it did not come close to providing a system that a rational person might consider trustworthy.

Even if the engineering on the phone were perfect, a scanner brings within the user’s trust perimeter all those involved in targeting it – in deciding which photos go on the naughty list, or how to train any machine-learning models that riffle through your texts or watch your videos. Even if it starts out trained on images of child abuse that all agree are illegal, it’s easy for both insiders and outsiders to manipulate images to create both false negatives and false positives. The more we look at the detail, the less attractive such a system becomes. The measures required to limit the obvious abuses so constrain the design space that you end up with something that could not be very effective as a policing tool; and if the European institutions were to mandate its use – and there have already been some legislative skirmishes – they would open up their citizens to quite a range of avoidable harms. And that’s before you stop to remember that the European Court of Justice struck down the Data Retention Directive on the grounds that such bulk surveillance, without warrant or suspicion, was a grossly disproportionate infringement on privacy, even in the fight against terrorism. A client-side scanning mandate would invite the same fate.

But ‘if you build it, they will come’. If device vendors are compelled to install remote surveillance, the demands will start to roll in. Who could possibly be so cold-hearted as to argue against the system being extended to search for missing children? Then President Xi will want to know who has photos of the Dalai Lama, or of men standing in front of tanks; and copyright lawyers will get court orders blocking whatever they claim infringes their clients’ rights. Our phones, which have grown into extensions of our intimate private space, will be ours no more; they will be private no more; and we will all be less secure.

Robots, manners and stress

Academic papers, Legal issues, Politics, Security engineering

Humans and other animals have evolved to be aware of whether we’re under threat. When we’re on safe territory with family and friends we relax, but when we sense that a rival or a predator might be nearby, our fight-or-flight response kicks in. Situational awareness is vital, as it’s just too stressful to be alert all the time.

We’ve started to realise that this is likely to be just as important in many machine-learning applications. Take as an example machine vision in an automatic driver assistance system, whose goal is automatic lane keeping and automatic emergency braking. Such systems use deep neural networks, as they perform way better than the alternatives; but they can be easily fooled by adversarial examples. Should we worry? Sure, a bad person might cause a car crash by projecting a misleading image on a motorway bridge – but they could as easily steal some traffic cones from the road works. Nobody sits up at night worrying about that. But the car industry does actually detune vision systems from fear of deceptive attacks!

We therefore started a thread of research aimed at helping machine-learning systems detect whether they’re under attack. Our first idea was the Taboo Trap. You raise your kids to observe social taboos – to behave well and speak properly – and yet once you send them to school they suddenly know words that would make your granny blush. The taboo violation shows they’ve been exposed to ‘adversarial inputs’, as an ML engineer would call them. So we worked out how to train a neural network to avoid certain taboo values, both of outputs (forbidden utterances) and intermediate activations (forbidden thoughts). The taboos can be changed every time you retrain the network, giving the equivalent of a cryptographic key. Thus even though adversarial samples will always exist, you can make them harder to find; an attacker can’t just find one that works against one model of car and use it against every other model. You can take a view, based on risk, of how many different keys you need.

We then showed how you can also attack the availability of neural networks using sponge examples – inputs designed to soak up as much energy, and waste as much time, as possible. An alarm can be simpler to build in this case: just monitor how long your classifier takes to run.

Are there broader lessons? We suspect so. As robots develop situational awareness, like humans, and react to real or potential attacks by falling back to a more cautious mode of operation, a hostile environment will cause the equivalent of stress. Sometimes this will be deliberate; one can imagine constant low-level engagement between drones at tense national borders, just as countries currently probe each others’ air defences. But much of the time it may well be a by-product of poor automation design coupled with companies hustling aggressively for consumers’ attention.

This suggests a missing factor in machine-learning research: manners. We’ve evolved manners to signal to others that our intent is not hostile, and to negotiate the many little transactions that in a hostile environment might lead to a tussle for dominance. Yet these are hard for robots. Food-delivery robots can become unpopular for obstructing and harassing other pavement users; and one of the show-stoppers for automated driving is the difficulty that self-driving cars have in crossing traffic, or otherwise negotiating precedence with other road users. And even in the military, manners have a role – from the chivalry codes of medieval knights to the more modern protocols whereby warships and warplanes warn other craft before opening fire. If we let loose swarms of killer drones with no manners, conflict will be more likely.

Our paper Situational Awareness and Machine Learning – Robots, Manners and Stress was invited as a keynote for two co-located events: IEEE CogSIMA and the NATO STO SCI-341 Research Symposium on Situation awareness of Swarms and Autonomous systems. We got so many conflicting demands from the IEEE that we gave up on making a video of the talk for them, and our paper was pulled from their proceedings. However we decided to put the paper online for the benefit of the NATO folks, who were blameless in this matter.

Infrastructure – the Good, the Bad and the Ugly

Cybercrime, Internet censorship, Legal issues, News coverage, Politics, Security economics, Social networks

Infrastructure used to be regulated and boring; the phones just worked and water just came out of the tap. Software has changed all that, and the systems our society relies on are ever more complex and contested. We have seen Twitter silencing the US president, Amazon switching off Parler and the police closing down mobile phone networks used by crooks. The EU wants to force chat apps to include porn filters, India wants them to tell the government who messaged whom and when, and the US Department of Justice has launched antitrust cases against Google and Facebook.

Infrastructure – the Good, the Bad and the Ugly analyses the security economics of platforms and services. The existence of platforms such as the Internet and cloud services enabled startups like YouTube and Instagram soar to huge valuations almost overnight, with only a handful of staff. But criminals also build infrastructure, from botnets through malware-as-a-service. There’s also dual-use infrastructure, from Tor to bitcoins, with entangled legitimate and criminal applications. So crime can scale too. And even “respectable” infrastructure has disruptive uses. Social media enabled both Barack Obama and Donald Trump to outflank the political establishment and win power; they have also been used to foment communal violence in Asia. How are we to make sense of all this?

I argue that this is not simply a matter for antitrust lawyers, but that computer scientists also have some insights to offer, and the interaction between technical and social factors is critical. I suggest a number of principles to guide analysis. First, what actors or technical systems have the power to exclude? Such control points tend to be at least partially social, as social structures like networks of friends and followers have more inertia. Even where control points exist, enforcement often fails because defenders are organised in the wrong institutions, or otherwise fail to have the right incentives; many defenders, from payment systems to abuse teams, focus on process rather than outcomes.

There are implications for policy. The agencies often ask for back doors into systems, but these help intelligence more than interdiction. To really push back on crime and abuse, we will need institutional reform of regulators and other defenders. We may also want to complement our current law-enforcement strategy of decapitation – taking down key pieces of criminal infrastructure such as botnets and underground markets – with pressure on maintainability. It may make a real difference if we can push up offenders’ transaction costs, as online criminal enterprises rely more on agility than on on long-lived, critical, redundant platforms.

This was a Dertouzos Distinguished Lecture at MIT in March 2021.

Friendly neighbourhood cybercrime: online harm in the pandemic and the futures of cybercrime policing

Academic papers, Cybercrime, Politics

As cybercrime researchers we’re often focused on the globalised aspects of online harms – how the Internet connects people and services around the world, opening up opportunities for crime, risk, and harm on a global scale. However, as we argue in open access research published this week in the Journal of Criminal Psychology in collaboration between the Cambridge Cybercrime Centre (CCC), Edinburgh Napier University, the University of Edinburgh, and Abertay University, as we have seen an enormous rise in reported cybercrime in the pandemic, we have paradoxically seen this dominated by issues with a much more local character. Our paper sketches a past: of cybercrime in a turbulent 2020, and a future: of the roles which state law enforcement might play in tackling online harm a post-pandemic world.

Continue reading Friendly neighbourhood cybercrime: online harm in the pandemic and the futures of cybercrime policing →