May 23, 2017

Innovation in Network Measurement Can and Should Affect the Future of Internet Privacy

As most readers are likely aware, the Federal Communications Commission (FCC) issued a rule last fall governing how Internet service providers (ISPs) can gather and share data about consumers that was recently rolled back through the Congressional Review Act. The media stoked consumer fear with headlines such as “For Sale: Your Private Browsing History” and comments about how ISPs can now “sell your Web browsing history to advertisers“. We also saw promises from large ISPs such as Comcast promising not to do exactly that. What’s next is anyone’s guess, but technologists need not stand idly by.

Technologists can and should play an important role in this discussion in several ways.  In particular, conveying knowledge about the capabilities and uses of network monitoring, and developing both new monitoring technologies and privacy-preserving capabilities can and should shape this debate in three important ways: (1) Level-setting on the data collection capabilities of various parties; (2) Understanding and limiting the power of inference; and (3) Developing new monitoring technologies that help facilitate network operations and security while protecting consumer privacy.

1. Level-setting on data collection uses and capabilities. Before entering a debate about privacy, it helps to have a firm understanding of who can collect what types of data—both in theory and in practice, as well as the myriad ways that data might be used for good (and bad). For example, in practice, if anyone has your browsing history, your ISP is a less likely culprit than an online service provider such as Google—who operates a browser, and (perhaps more importantly) whose analytics scripts are on a large fraction of the Internet’s web pages. Your browsing is also likely being logged by many of the countless online trackers that keep track of your browsing history, often without your knowledge or consent. In contrast, the network monitoring technology that is available in routers and switches today makes it a lot more difficult to extract “browsing history”; that requires a technology commonly referred to as “deep packet inspection” (DPI), or complete capture of network traffic data, which is expensive to deploy, and even more costly when data storage and analysis is concerned. Most ISPs will tell you than DPI is deployed on only a small fraction of the links in their networks, and that fraction is going down as speeds are increasing; it’s expensive to collect and analyze all of that data.

ISPs do, of course, collect other types of traffic statistics, such as lookups to domain names via the Domain Name System (DNS) and coarse-grained traffic volume statistics via IPFIX. That data can, of course, be revealing. At the same time, ISPs will correctly point out that monitoring DNS and IPFIX is critical to securing and operating the network. DNS traffic, for example, is central to detecting denial of service attacks or infected devices. IPFIX statistics are critical for monitoring and mitigating network congestion. DNS is a quintessential example of data that is both incredibly sensitive (because it reveals the domains and websites we visit, among other things, and is typically unencrypted) and incredibly useful for detecting attacks, ranging from phishing to denial of service attacks.

The long line of security and traffic engineering research illustrates both the importance of data collection, as well as the limitations of current network monitoring capabilities in performing these tasks. Take, for example, research on botnet detection, which has shown the power of using DNS lookup data and IPFIX statistics for detecting compromise and intrusion. Or, the development of traffic engineering capabilities in the data center and in the wide area, which depend on the collection and analysis of IPFIX records and in some cases packet traces.

2. Understanding (and mitigating) the power of inference. While most of the focus in the privacy debate thus far concerns data collection (specifically, a focus on DPI, which is somewhat misguided per the discussion above), we would be wise to also consider what can be inferred from any data that is collected. For example, various aspects of “browsing history” could be evident from various datasets ranging from DNS to DPI, but as discussed above all of these datasets also have legitimate operational uses. Furthermore, “browsing history” is evident from a wide range of datasets that many parties are privy to without our consent, beyond just ISPs. Such inference capabilities are only going to increase with the proliferation of data-producing Internet-connected devices coupled with advances in machine learning. If prescriptive rules specify which some types of data can be collected, we risk over-prescribing rules, while failing to achieve the goal of protecting the higher-level information that we really want to protect.

While asking questions about collection is a fine place to start a discussion, we should be at least as concerned with how the data is usedwhat it can be used to infer, and who it is shared with.We likely should be asking: (1) What data do we think should be protected or private? (2) What types network data permits inference of that private data? (3) Who has access to that data and under what circumstances? Suppose that I am interested in protecting information about whether I am at home. My ISP could learn this information from my traffic patterns, simply based on the decline in traffic volume from individual devices, even if all of my web traffic were encrypted, and even if I used a virtual private network (VPN) for all of my traffic. Such inference will be increasingly possible as more devices in our homes connect to the Internet. But, online service providers could also come to know the same information without my consent, based on different data; Google, for example, would know that I’m browsing the web at my office, rather than at home, through the use of technologies such as cookies, browser fingerprinting, and other online device tracking mechanisms.

Past and ongoing research, such as the Web Transparency and Accountability Project, as well as the “What They Know” series from the Wall Street Journal, shed important light on what can be inferred from various digital data sources. The Upturn report last year was similarly illuminating with respect to ISP data. More recently, researchers at Princeton including Noah Apthorpe and Dillon Reisman have been developing techniques to mitigate the power of inference using various traffic shaping and camouflaging techniques to limit what an ISP can infer from traffic patterns coming from a home network.

3. Facilitating purpose-driven network measurement and data minimization. Part of the tension surrounding network measurement and privacy is that current network monitoring technology is very crude; in fact, this technology hasn’t changed considerably in nearly 30 years. It at once gathers too much data, and yet, for many purposes, it is still too little. Consider, for example, that with current network monitoring technology, an ISP (or content provider) have incredible difficulty determining a user’s quality of experience for a given application, such as video streaming, simply because the wrong kind of data is collected, at the wrong granularity. As a result, ISPs (and many other parties in the Internet ecosystem) adopt a post hoc “collect first, ask questions later” approach, simply because current network monitoring technology (1) is oriented towards offline processing on warehoused data; (2) does not make it easy to figure out what data is needed to answer a particular analysis question.

Instead, network data collection could be driven by the questions operators were asking; data could be collected if—and only if—it were pertinent to a specific question or network operations task, such as monitoring application performance or detecting attacks. For example, suppose that an operator could ask a query such as “tell me the average packet loss rate of all Netflix video streams for subscribers in Seattle”. Answering such a query with today’s tools is challenging: one would have to collect all packet traces and all DNS queries and somehow identify post hoc that these streams correspond to the application of interest. In short, it’s difficult, if not impossible, answer such an operational query today without large-scale collection and storage of (very sensitive) data—all to find what is essentially a needle in a haystack.

Over the past year, my Ph.D. student Arpit Gupta at Princeton has been leading the design and development of a system called Sonata that may ultimately resolve this dichotomy and give us the best of both worlds. Two emerging technologies—(1) in-band network measurement, as supported by Barefoot’s Tofino chipset; (2) scalable streaming analytics platforms such as Spark—make it possible to write a high-level query in advance and only collect the data that is needed to satisfy the query. Such technology allows a network operator to write a query in a high-level language (in this case, Scala), specifying only the question, but allowing the runtime to figure out the minimal set of raw data that is needed to satisfy the operator’s query.

Our goal in the design and implementation of Sonata was to satisfy the operational and scaling limitations of network measurement, but achieving such scalability also has data minimization effects that have positive benefits for privacy. Data that is collected can also be a liability; it may, for example, become the target of law enforcement requests or subpoenas, which parties such as ISPs, but also online providers such as Google are regularly subject to. Minimizing the collected data to only that which is pertinent to operational queries can also ultimately help reduce this risk.

Sonata is open source, and we welcome contributions and suggestions from the community about how we can better support specific types of network queries and tasks.

Summary. Network monitoring and analytics technology is moving at a rapid pace, in terms of its capabilities to help network operators answer important questions about performance and security, without coming at the cost of consumer privacy. Technologists should devote attention to developing new technologies that can help achieve the best of both worlds, and on helping educate policymakers about the capabilities (and limitations) of existing network monitoring technology. Policymakers should be aware that network monitoring technology continues to advance, and should focus discussion around protecting what can be inferred, rather than focusing only on who can collect a packet trace.

Multiple Intelligences, and Superintelligence

Superintelligent machines have long been a trope in science fiction. Recent advances in AI have made them a topic for nonfiction debate, and even planning. And that makes sense. Although the Singularity is not imminent–you can go ahead and buy that economy-size container of yogurt–it seems to me almost certain that machine intelligence will surpass ours eventually, and quite possibly within our lifetimes.

Arguments to the contrary don’t seem convincing. Kevin Kelly’s recent essay in Backchannel is a good example. His subtitle, “The AI Cargo Cult: The Myth of a Superhuman AI” implies that AI of superhuman intelligence will not occur. His argument centers on five “myths”:

  1. Artificial intelligence is already getting smarter than us, at an exponential rate.
  2. We’ll make AIs into a general purpose intelligence, like our own.
  3. We can make human intelligence in silicon.
  4. Intelligence can be expanded without limit.
  5. Once we have exploding superintelligence it can solve most of our problems.

He rebuts these “myths” with five “heresies” :

  1. Intelligence is not a single dimension, so “smarter than humans” is a meaningless concept.
  2. Humans do not have general purpose minds, and neither will AIs.
  3. Emulation of human thinking in other media will be constrained by cost.
  4. Dimensions of intelligence are not infinite.
  5. Intelligences are only one factor in progress.

This is all fine, but notice that even if all five “myths” are false, and all five “heresies” are true, superintelligence could still exist.  For example, superintelligence need not be “like our own” or “human” or “without limit”–it only needs to outperform us.

The most interesting item on Kelly’s lists is heresy #1, that intelligence is not a single dimension, so “smarter than humans” is a meaningless concept. This is really two claims, so let’s consider them one at a time.

First, is intelligence a single dimension, or are there different aspects or skills involved in intelligence?  This is an old debate in human psychology, on which I don’t have an informed opinion. But whatever the nature and mechanisms of human intelligence might be, we shouldn’t assume that machine intelligence will be the same.

So far, AI practice has mostly treated intelligence as multi-dimensional, building distinct solutions to different cognitive challenges. Perhaps this is fundamental, and machine intelligence will always be a bundle of different capabilities. Or perhaps there will be a future unification of some sort, to create a single capability that can outperform people on all or nearly all cognitive tasks. At this point it seems like an open question whether machine intelligence is inherently multi-dimensional.

The second part of Kelly’s claim is that, assuming intelligence is multi-dimensional, “smarter than humans” is a meaningless concept. This, to put it bluntly, is not correct.

To see why, consider that playing center field in baseball requires multi-dimensional skills: running, throwing, distinguishing balls from strikes, hitting accurately, hitting with power, and so on. Yet every single major league center fielder is vastly better than I am at playing center field, because they dominate me by far in every one of the component skills.

Like playing center field, intelligence may be multi-dimensional, and yet one entity can be more intelligent than another by being superior in every dimension.

What this suggests about the future of machine intelligence is that we may live for quite a while in a state where machines are better than us at some aspects of intelligence and we are better than them at others. Indeed, that is the case now, and has been for years.

If machine intelligence remains multi-dimensional, then machines will surpass our intelligence not at a single point in time, but gradually, and in more and more dimensions of intelligence.

The future of ad blocking

There’s an ongoing arms race between ad blockers and websites — more and more sites either try to sneak their ads through or force users to disable ad blockers. Most previous discussions have assumed that this is a cat-and-mouse game that will escalate indefinitely. But in a new paper, accompanied by proof-of-concept code, we challenge this claim. We believe that due to the architecture of web browsers, there’s an inherent asymmetry that favors users and ad blockers. We have devised and prototyped several ad blocking techniques that work radically differently from current ones. We don’t claim to have created an undefeatable ad blocker, but we identify an evolving combination of technical and legal factors that will determine the “end game” of the arms race.

Our project began last summer when Facebook announced that it had made ads look just like regular posts, and hence impossible to block. Indeed, Adblock Plus and other mainstream ad blockers have been ineffective on Facebook ever since. But Facebook’s human users have to be able to tell ads apart because of laws against misleading advertising. So we built a tool that detects Facebook ads the same way a human would, deliberately ignoring hidden HTML markup that can be obfuscated. (Adblock Plus, on the other hand, is designed to be able to examine only the markup of web pages and not the content.) Our Chrome extension has several thousand users and continues to be effective.

We’ve built on this early success. Laws against misleading advertising apply not just on Facebook, but everywhere on the web. Due to these laws and in response to public-relations pressure, the online ad industry has developed robust self-regulation that standardizes the disclosure of ads across the web. Once again, ad blockers can exploit this, and that’s what our perceptual ad blocker does. [1]

The second prong of an ad blocking strategy is to deal with websites that try to detect (and in turn block) ad blockers. To do this, we introduce the idea of stealth. The only way that a script on a web page can “see” what’s drawn on the screen is to ask the user’s browser to describe it. But ad blocking extensions can control the browser! Not perfectly, but well enough to get the browser to convincingly lie to the web page script about the very existence of the ad blocker. Our proof-of-concept stealthy ad blocker successfully blocked ads and hid its existence on all 50 websites we looked at that are known to deploy anti-adblocking scripts. Finally, we have also investigated ways to detect and block the ad blocking detection scripts themselves. We found that this is feasible but cumbersome; at any rate, it is unnecessary as long as stealthy ad blocking is successful.

The details of all these techniques get extremely messy, and we encourage the interested reader to check out the paper. While some of the details may change, we’re confident of our long-term assessment. That’s because our techniques are all based on sound computer security principles and because we’ve devised a state diagram that describes the possible actions of websites and ad blockers, bringing much-needed clarity to the analysis and helping ensure that there won’t be completely new techniques coming out of left field in the future.

There’s a final wrinkle: the publishing and advertising industries have put forth a number of creative reasons to argue that ad blockers violate the law, and indeed Adblock Plus has been sued several times (without success so far). We carefully analyzed four bodies of law that may support such legal claims, and conclude that the law does not stand in the way of deploying sophisticated ad blocking techniques. [2] That said, we acknowledge that the ethics of ad blocking are far from clear cut. Our research is about what can be done and not what should be done; we look forward to participating in the ethical debate.


[1] To avoid taking sides on the ethics of ad blocking, we have deliberately stopped short of making our proof-of-concept tool fully functional — it is configured to detect ads but not actually block them.

[2] One of the authors is cyberlaw expert Jonathan Mayer.