Our research seeks to empower individuals and organizations to control how their data is used. We use techniques from cryptography, programming languages, machine learning, and other areas to both understand and improve the security of computing as practiced today, and as envisioned in the future.

Security Research Group (19 January 2016)
Jack Doerner, Samee Zahur, Mahnush Movahedi, Mohammad Etemad, Haina Li, Weilin Xu, Karen Pan


Secure Multi-Party Computation
Obliv-C · MightBeEvil
Practical Secure Computation
Web and Mobile Security
ScriptInspector · SSOScan
Side-Channel Analysis · Social Networking APIs
Adversarial Machine Learning
Program Analysis
Perracotta · N-Variant Systems · Physicrypt · Splint


Tracking Congressional Phones

April 18th, 2016 by David Evans

Karsten Nohl (SRG CpE PhD 2009) was on CBS’ 60 Minutes (April 17) as their “Moment of the Week”: Hacking into a congressman’s phone.

We heard we could find some of the world’s best hackers in Germany. So we headed for Berlin. Just off a trendy street and through this alley we rang the bell at the door of a former factory. That’s where we met Karsten Nohl, a German hacker, with a doctorate in computer engineering from the University of Virginia.


Karsten demonstrated to the reporter how to track a Congressman’s location and listen in on phone conversations using SS7 vulnerabilities (for a real Congressman, Ted Liu of California, who actually has a CS degree). With permission, of course!

We wanted to see whether Nohl’s group could actually do what they claimed — so we sent an off-the-shelf iPhone from 60 Minutes in New York to Representative Ted Lieu, a congressman from California. He has a computer science degree from Stanford and is a member of the House committee that oversees information technology. He agreed to use our phone to talk to his staff knowing they would be hacked and they were. All we gave Nohl, was the number of the 60 Minutes iPhone that we lent the congressman.

An excerpt from the show was also the 60 Minutes Moment of the Week.

An exercise in password security went terribly wrong, security experts say

April 1st, 2016 by David Evans

PCWord has a story about CNBC’s attempt to “help” people measure their password security: CNBC just collected your password and shared it with marketers: An exercise in password security went terribly wrong, security experts say, 29 March 2016.

Adrienne Porter Felt, a software engineer with Google’s Chrome security team, spotted that the article wasn’t delivered using SSL/TLS (Secure Socket Layer/Transport Layer Security) encryption.

SSL/TLS encrypts the connection between a user and a website, scrambling the data that is sent back and forth. Without SSL/TLS, someone one the same network can see data in clear text and, in this case, any password sent to CNBC.

“Worried about security? Enter your password into this @CNBC website (over HTTP, natch). What could go wrong,” Felt wrote on Twitter. “Alternately, feel free to tweet your password @ me and have the whole security community inspect it for you.”

The form also sent passwords to advertising networks and other parties with trackers on CNBC’s page, according to Ashkan Soltani, a privacy and security researcher, who posted a screenshot.

Despite saying the tool would not store passwords, traffic analysis showed it was actually storing them in a Google Docs spreadsheet, according to Kane York, who works on the Let’s Encrypt project.

(Posted on April 1, but this is actually a real story, as hard as that might be to believe.)

Spectra Articles: Privacy-Preserving Regression and Ombuds

March 21st, 2016 by David Evans

The latest edition of Spectra: The Virginia Engineering and Science Research Journal includes two articles about SRGers!

The first is an article about Sam Havron’s research on using MPC to perform linear regression for social science applications: [PDF]

alt : Ombuds.pdf

The second is by Alex Kuck and Nick Skelsey on their work on using a blockchain to provide censorship-resistant messaging: Ombuds: A Public Space with a Single Shared History: [PDF]

alt : Ombuds.pdf

The full issue is available at the Spectra site (thanks to Garrett Beeghly for granting permission to post these excerpts here).

Apple and the FBI

February 25th, 2016 by David Evans

I’m quoted in this article on the controversy over the FBI’s requests to Apple for assistance in unlocking an iPhone used by one of the San Bernardino terrorists: Unlocking Terrorist’s iPhone Won’t Risk Your Security, Discovery News, 24 February 2016.

“Backdoors are complicated and impossible technical challenges and would risk everyone’s privacy,” Evans said. “But what the FBI is asking for is different from what Apple says the FBI is asking for.”

For the most part, I think the article gets things right. It is very misleading to conflate what the FBI has asked for here with a cryptographic backdoor that would indeed dangerously risk everyone’s privacy and security. I covered some of the technical aspects of this in my introductory computing course last week.

NDSS Talk: Automatically Evading Classifiers (including Gmail’s)

February 24th, 2016 by David Evans

Weilin Xu presented his work on Automatically Evading Classifiers today at the Network and Distributed Systems Security Symposium in San Diego, CA (co-advised by Yanjun Qi and myself). The work demonstrates an automated approach for finding evasive variants of malicious PDF files using genetic programming techniques. Starting with a malicious seed file (that is, a PDF file with the intended malicious behavior, but that is correctly classified as malicious by the target classifier), it heuristically searches for an evasive variant that preserves the malicious behavior of the seed sample but is now classified as benign. The method automatically found an evasive variant for every seed in our test set of 500 malicious PDFs for both of the target classifiers used in the experiment (PDFrate and Hidost).

Slides from the talk are below, the full paper and code is available on the EvadeML.org website.

In addition to the results in the paper, Weilin found some new results examining gmail’s PDF malware classifier. We had hoped the classifier used by gmail would be substantially better than what we found in the research prototype classifiers used in the original experiments, and the initial cross-evasion experiments supported this. Of the 500 evasive variants found for Hidost in the original experiment, 387 were also evasive variants against PDFrate, but only 3 of them were evasive variants against Gmail’s classifier.

From those 3, and some other manual tests, however, Weilin was able to find two very simple transformations (any change to JavaScript such as adding a variable declaration, and adding padding to the file) that are effective at finding evasive variants for 47% of the seeds.

The response we got from Google about this was somewhat disappointing (and very inconsistent with my all previous experiences raising security issues to Google):

Its true, of course, that any kind of static program analysis is theoretically impossible to do perfectly. But, that doesn’t mean the dominant email provider shouldn’t be trying to do better to detect one of the main vectors for malware distribution today (and there are, we believe, many fairly straightforward and inexpensive things that could be done to do dramatically better than what Gmail is doing today).

The other new result in the talk that isn’t in the paper is the impact of adjusting the target classifier threshold. The search for evasive variants can succeed even at lower thresholds for defining maliciousness (as shown in the slide below, finding evasive variants against PDFrate at the 0.25 maliciousness threshold).

Weilin’s Summer of Code

February 5th, 2016 by David Evans

Google’s Open Source blog has a story by Weilin Xu about his experiences in their Summer of Code before he came to UVA: Coming to America: how Google Summer of Code helped change my life, 3 February 2016.

Latest from Karsten Nohl: POS Security

December 30th, 2015 by David Evans

Karsten Nohl (PhD 2009) presented his work (with Fabian Bräunlein and Philipp Maier) on vulnerabilities in payment protocols (the ones studied are widely used in Germany but not in other countries) at the Chaos Communications Congress on December 27.

The work has been widely covered in the press recently. Here are a few sample articles:

- Watch infosec bods swipe PINs, magstripe data from card readers live on stage, The Register, 30 Dec 2015. (I trust the use of “bods” here is some kind of Britishism, not what it means in American.)

Now let’s look at Poseidon: a crook can buy a Poseidon payment terminal from the internet, and configure it to pretend to be a particular merchant’s systems. To do this, you need three bits of information, which are trivial to obtain…. Now you can perform arbitrary refunds, drawing money from the store’s funds. As there is no interruption to a merchant’s service, the seller will be none the wiser until he or she audits their finances. … German banks have shrugged off their research as merely “theoretical.”

- Payment system security is hilariously bad, BoingBoing (Cory Doctorow), 29 Dec 2015.

- Worries over German retail payments risks, Reuters, 23 December 2015.

A top cyber security researcher has warned German banks that their retail payment systems have security flaws that could allow fraudsters to steal payment card PIN codes, create fake cards or siphon funds from customer or merchant accounts.
Karsten Nohl, who is credited with revealing major security threats in mobile phones, automobiles, security cards and thumb-sized USB drives, told Reuters he has found critical weaknesses in software that runs retail point-of-sale terminals in Germany.

Dormant Malicious Code Discovered on Thousands of Websites

December 29th, 2015 by David Evans

Here’s the latest from Yuchen Zhou (PhD 2015, now at Palo Alto Networks): Dormant Malicious Code Discovered on Thousands of Websites, Yuchen Zhou and Wei Xu, Palo Alto Networks Blog, 14 November 2015.

During our continuous monitoring for a 24-hour period from November 11, 2015 to November 12, 2015, eight days after the initial discovery, the Chuxiong Archives website consistently presented malicious content injected by an attacker depending on the source IP and user agent. We believe that if a user were to visit the compromised website a second time following the initial exposure to the malicious code, the site would recognize the source IP and user-agent and simply remain dormant, not exhibiting any malicious behavior. Because of this anti-analysis/evasion technique, it may easily cause the belief that a website no longer poses a threat, when it remains infected.

At the time of this report, using our malicious web content scanning system, we have already discovered more than four thousands additional, similarly compromised websites globally exhibiting the same ability of being able to be dormant or active depending on source IP and user agent. Investigations regarding this campaign on a larger scale are ongoing and a second report detailing the similarly compromised websites will be published in the near future.

Evading Machine Learning Classifiers

December 21st, 2015 by David Evans

Today we’re releasing our paper on evading machine learning classifiers:

Weilin Xu, Yanjun Qi, and David Evans. Automatically Evading Classifiers: A Case Study on PDF Malware Classifiers Network and Distributed System Security Symposium (NDSS). San Diego, CA. 21-24 February 2016. [PDF, 15 pages]

The main idea behind the paper is to explore how an adaptive adversary can evade a machine learning-based malware classifier by using techniques from genetic programming to automatically explore the space of potential evasive variants.

In a case study using two PDF malware classifiers as targets, we find that it is possible to automatically find evasive variants (that is, variants that preserve the desired malicious behavior while being (mis)classified as benign) for all 500 seeds in our test dataset.

Weilin Xu will present the work at the Network and Distributed Systems Security Symposium in San Diego in February.

For more, see EvadeML.org or the full paper (PDF).

Computer Science Grad Stands Watch for Users of Google’s Popular Browser

December 8th, 2015 by David Evans

Adrienne Porter Felt (BSCS 2008) returned to UVa last Friday as a Distinguished Alumni Speaker. UVa Today published this article:

Computer Science Grad Stands Watch for Users of Google’s Popular Browser
, UVa Today, 7 December 2015.

Adrienne Porter Felt’s job is to keep you secure on Chrome.

Felt, 29, who earned a computer science degree from the University of Virginia in 2008, leads the usable security team at Google working on the popular Internet browser.

Taking Evans’ offer for a research project was a turning point in Felt’s life, showing her something she liked that she could do well.

“It turned out that I really loved it,” she said. “I like working in privacy and security because I enjoy helping people control their digital experiences. I think of it as, ‘I’m professionally paranoid so that other people don’t need to be.’”