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October 18 2012

Quantitative Analysis of the Full Bitcoin Transaction Graph

Dorit Ron and Adi Shamir

Abstract: The Bitcoin scheme is a rare example of a large scale global payment system in which all the transactions are publicly accessible (but in an anonymous way). We downloaded the full history of this scheme, and analyzed many statistical properties of its associated transaction graph. In this paper we answer for the first time a variety of interesting questions about the typical behavior of account owners, how they acquire and how they spend their Bitcoins, the balance of Bitcoins they keep in their accounts, and how they move Bitcoins between their various accounts in order to better protect their privacy. In addition, we isolated all the large transactions in the system, and discovered that almost all of them are closely related to a single large transaction that took place in November 2010, even though the associated users apparently tried to hide this fact with many strange looking long chains and fork-merge structures in the transaction graph.

Category / Keywords: Bitcoin, digital coins, electronic cash, payment systems, transaction graphs, quantitative analysis

Cryptology ePrint Archive: Report 2012/584
Reposted fromqueitsch queitsch

December 21 2011

Android No-Permissions Reverse Shell
Reposted fromastera astera

December 17 2011

EFF's Sovereign Keys project aims to make the encrypted Internet more reliable and secure. It is a proposal to fix structural insecurities in the way that the Web, Email and other Internet protocols currently establish encrypted connections.

If deployed, Sovereign Keys will protect HTTPS and other uses of TLS/SSL against a wide variety of attacks, including attacks involving Certificate Authorities and domain validation, and attacks that involve downgrading or blocking encrypted connections. It operates by providing an optional and very secure way of associating domain names with public keys, augmenting other methods of publishing TLS/SSL keys, such as the existing system of Certificate Authorities or proposals to publish keys via DNSSEC.

You can read a high level overview or look at the detailed design document and list of issues that we're tracking in relation to the design.

The Sovereign Keys Project | Electronic Frontier Foundation
Reposted fromqueitsch queitsch

December 01 2011

chpwn blog: Carrier IQ is on iOS


Carrier IQ, the now infamous “rootkit” or “keylogger”, is not just for Android, Symbian, BlackBerry, and even webOS. In fact, up through and including iOS 5, Apple has included a copy of Carrier IQ on the iPhone. However, it does appears to be disabled along with diagnostics enabled on…

Reposted fromqueitsch queitsch

November 22 2011

Introduction to IDA Python

The Introduction to IDA Python document by Ero Carrera is one of the better documents on scripting the IDA Pro platform available. After talking with Ero directly, I have received permission to host the PDF directly on Offensive Computing to make it available long-term. Enjoy.

Introduction to IDA Python by Ero Carrera


Reposted fromsec sec

October 22 2011

Post-CCS reading recommendations

Now that the 18th ACM Conference on Computer and Communication Security (CCS) is over, here is my list of papers worth reading (clearly biased and non-exhaustive). This is not necessarily an outright recommendation for the respective publication, more of a to-do list for myself, as by now I have yet to read a fair part of the list below; some papers I just scanned through after receiving the proceedings, some made it on the list because I liked the talk or took something out of it. The list is ordered chronologically.

In their paper On the Requirements for Successful GPS Spoofing Attacks (pdf) Tippenhauer et al. explore the feasibility of practical attacks on the Global Positioning System and show that an attacker's signal needs to be only 2dB stronger than the benign GPS signal to successfully spoof the signal. While there are indeed a lot of constrains to be fulfilled (inter alia that the victims precise position has to be known to the attacker at any time and there is a limited set of positions the attacker may choose), the authors show that they can indeed have an impact on how the victim perceives her position.

The next paper, On the Vulnerability of FPGA Bitstream Encryption Against Power Analysis Attacks (pdf), is still in the hardware/signal hacking field: Moradi et al. use power analysis to recover the keys used for the triple DES bitstream encryption engine integrated in the widespread Virtex-II Pro FPGAs from Xilinx effectivly allowing for the cloning and manipulating of any real-world product based on these FPGAs.

Moving over to the web topics, there is Fashion Crimes: Trending-Term Exploitation on the Web (pdf) by Moore et al. The authors conduct a large-scale measurement study to analyze the prevalence of malware and pure advertising sites (so called "Made for AdSense", MFA sites) in trending term search results, and propose heuristics to identify such sites. As the data set used happens to span over the time where Google changed its page rank algorithm to counter the relatively large numbers of useless sites in its trending topics results, the authors where able to observe the impact of these measures. The paper also provides a nice amount of statistical data on malware and MFA in web search and Twitter results, the duration of such campaigns, which topic categories are hit how hard and so on. Personally, I am grateful that the authors compiled these statistics, as empirical results are often a useful thing to have. (The authors also do a better job summarizing their work here, than I did above.)

Next in the Wild Wooly Web session was SURF: Detecting and Measuring Search Poisoning (pdf) by Long Lu et al. which is on my reading list and deals with, well, the detection of search poisoning. The authors apply a supervised learning method to classify search results using a set of features derived from browser events, network info and the search results itself.

Switching over to malware I have The Power of Procrastination: Detection and Mitigation of Execution-Stalling Malicious Code (pdf) by Kolbitsch et al. on my list that deals with countering the analysis evasion technique of stalling code. Stalling code is unconditionally executed before any malicious activity takes place, as the malware author hopes that an automated analysis system will give up on the sample before anything meaningful happens and the sample is consequently flagged as dysfunctional.

Next on the list is Breaking XML-Encryption (pdf) by Jager and Somorovsky, which is a great example of colliding worlds (here: the XML/web services universe receives a solid blow by cryptology) . While using 3DES or AES the XML Encryption standard requires the application of CBC mode for messages that are longer than the cipher's block length. By performing a chosen-ciphertext attack the authors are able to decrypt a ciphertext by performing only 14 requests per plaintext byte on average and are able to successfully attack all implementations of XML Encryption currently used.

Back to the web there are two more papers on the recommendation list: the first one is Fear the EAR: Discovering and Mitigating Execution After Redirect vulnerabilities (pdf) by Adam Doupé et al. EAR is not completely new to world, at least in the PHP world this seems to be known for a while, but as the authors state correctly, it is not widely known. Still, the paper explores this topic in-depth, providing analysis of nine web application frameworks (i.a. RoR, Grails, Django, Struts). The authors also developed a static analysis tool for Ruby on Rails that has a high detection rate for this kind of logic flaw and errs a bit on the side of caution. I like the talk quite a bit, also due to the fact that it was one of the few that had some code samples for illustration where it was appropriate.

The second one is Automated Black-Box Detection of Side-Channel Vulnerabilities in Web Applications (pdf) by Chapman and Evans. The authors present a new metric based on the Fisher criterion to reveal side-channel data leaks in web applications, while also showing that HTTPOS is a valid approach to seal such information leaks.

The next to publications received quite a bit media attention, so I will not go into detail: iSpy: Automatic Reconstruction of Typed Input from Compromising Reflections (pdf) by Raguram et al. could also have been named "Pwning the cool" (thanks, Mario :) ), as the authors show that it is very well feasible to automatically reconstruct what a user typed into her mobile phone from the reflection in her sunglasses and also just by shoulder-surfing from quite a distance (>60m using an off-the-shelf camera). The other one is (sp)iPhone: Decoding Vibrations from Nearby Keyboards Using Mobile Phone Accelerometers by Marquardt et al., who showed how the accelerometer of a standard iPhone can be used to reconstruct what a user typed on her computer keyboard. The approach works way better on a wooden desk than on a tile floor, but as the authors pointed out correctly: who would type on a tile floor?

Context-Sensitive Auto-Sanitization in Web Templating Languages Using Type Qualifiers (pdf) by Samuel et al. proposes a novel approach to defend against scripting vulnerabilities in web applications which is already widely used, as it implemented in Google's Closure Templates, a framework that is used in GMail and other Google Applications. An intriguing feature is that this approach retrofits to existing template code without requiring any changes.

Next on my list is Android Permissions Demystified (pdf) by Porter Felt et al. who conducted a very detailed analysis of how permissions are used by Android applications resp. their developers. The authors developed a dynamic analysis tool, called Stowaway, to determine, whether an app really requires the permission that are requested in its manifest. While the authors do not provide a direct way to de-privilege an overprivileged application, they do a great job of explaining how Android handles permissions and which API call requires which permission. While the Android 2.2 documentation specifies permission requirements for 78 methods, the authors provide a permission map and identify 1,259 API calls with permission checks. This is a recommended read for anyone fooling around with (or doing serious work on) Android. The authors also provide Stowaway as an online service and offer the complete results of their mapping efforts as download on  android-permissions.org.

Raluca Ada Popa presented on Privacy and Accountability for Location-based Aggregate Statistics (pdf). Their system, PrivStats, aims to accomplish two goals: first, provable guarantees on location privacy even in the face of any side information about users known to the server, and second, privacy-preserving accountability (i.e., protection against abusive clients uploading large amounts of spurious data). While the authors focus on the application of location-based data, the protocols described here could also be used in other context where one wants to collect data from distributed, user-operated sensors, while on the one hand preserving their privacy and on the other hand preventing the database from being poisoned by a malicious user.

Finally, if you care for web and/or browser security, I can also recommend our own paper Crouching Tiger - Hidden Payload (pdf) that sheds a light on security risks of Scalable Vector Graphics and also describes a mitigation approach we call SVGPurifier. Feel free to try to bypass SVGPurifier here.

September 02 2011

The Longstanding KVGB Compromise

Our friends at Zscaler has blogged about a website compromise involving Karnataka Vikas Grameena Bank (KVGB), a prominent regional rural bank in India, last February of this year. It then housed a malicious JavaScript (JS) code that redirects visitors to another domain that was believed to be malicious at one point. The code had been found to be "multilevel obfuscated". Also according to the entry, they have informed the said bank about the code injected on their website.

As of 11:05PM (GMT–4:00) of August 25, six months after the said blog is published, GFI Senior Exploit Analyst Francesco Benedini is alerted about KVGB still housing obfuscated JS code. Below is the screenshot of the code found on the site:

(click to enlarge)

After deobfuscation, Benedini has determined that the supposedly malicious domain is inactive, thus, poses no threat to bank site visitors. The script, however, is working. We detect the malicious code as Trojan-Downloader.JS.Twettir.a (v), and VirusTotal shows a 24/43 detection ratio across all AV companies.

Our experts have also pointed out that the attack is related to the MBR rootkit (Trojan-Spy.Madlo) we generally know as Sinowal / Mebroot. This is because (1) the obfuscation technique used in this attack is reminiscent of the technique used by Sinowal, and (2) the structure of the inactive URL follows the one seen in Sinowal infection campaigns.

GFI is currently attempting to reach KVGB in order to help them clean up their website.

Jovi Umawing (Thanks to Adam Thomas for additional information)

Reposted fromsec sec

August 10 2011

Thanks for reporting an issue with Opera. While you are correct that Opera Mini does not display a certificate warning about chains with unknown Root certificates, there is, however, a significant difference between what happened in iOS and what happens in Opera Mini. Opera Mini will not indicate that such pages are secure, that is, no padlock or similar indication is displayed for the web site affected by this, giving the same security indications as it would for an unencrypted site, which is the same as would have been displayed if the user manually accepted the certificate. Not showing a dialog was a design decision by the Opera Mini team, due to the transcoder architecture of Opera Mini, and in part the complexity of having the transcoder (proxy) server display a dialog at the device and the obtain the result before continuing. For more about Opera Mini security see http://www.opera.com/mobile/help/faq/#security.

However, the URL in the address bar still says https:// with no indication that anything might be wrong with that. Judging from the user feedback we received, it is not clear to the users that the absense of the padlock means that the certificate validation failed.
In our emulation environment, we also discovered that on small screen devices, the padlock might not even be on-screen when loading a site.
CVE-2011-0228 and the Opera Mini UI-Design | The Recurity Lablog

August 06 2011

As part of a new initiative, called Cyber Fast Track, described Thursday at the Black Hat confernce in Las Vegas, the U.S. Defense Department will fund small hacker groups and independent researchers in the development of cutting-edge solutions that can be created in short intervals for a low cost.

The program is the brainchild of Peiter Zatko, a respected hacker known as “Mudge,” who last February took on the role of program manager at the Defense Advanced Research Projects Agency (DARPA), the Defense Department's central research organization.

“Small groups of motivated and like-minded researchers have repeatedly shown talent and capability,” Zatko said in his keynote speech. “I want the people out there doing the cool research work.”

The program aims to make it easier for independent researchers to obtain government funding for cybersecurity projects, he said. Historically, federal security funding has been awarded to large contractors that often have whole teams dedicated to crafting proposals. Under the current system, it is difficult for an independent researcher to be awarded funding due to the time and cost of the application process alone.

“Welcome to the new DARPA,” Zatko said.

The program, in development for the past eight months, will fund between 20 and 100 projects each year, addressing a range of cybersecurity issues, Zatko said. Those who are chosen to participate can retain their own intellectual property.


US internet providers hijacking users' search queries

The hijacking seems to target searches for certain well-known brand names only. Users entering the term "apple" into their browser's search bar, for example, would normally get a page of results from their search engine of choice. The ISPs involved in the scheme intercept such requests before they reach a search engine, however. They pass the search to an online marketing company, which directs the user straight to Apple's online retail website.

More than 10 ISPs in the US, which together have several million subscribers, are redirecting queries in this way (see below for a complete list). None of the companies would comment on the redirection scheme, but evidence collected by Christian Kreibich and Nicholas Weaver at the International Computer Science Institute in Berkeley, California, who discovered the redirection and have been monitoring it for several months, suggest that the process generates revenue for the ISPs.

US internet providers hijacking users' search queries - tech - 04 August 2011 - New Scientist

August 05 2011

Here's another thing that's scary about Shady RAT

A lot of chatter and breathless reporting about Shady RAT.  All the makings of an epically awesome story — the US is being taken down by Chinese interlopers to the nastiest degree, installing keyloggers and other badness on US government computers. 

Whatever.  Who the heck knows how bad this thing really is (and I am not the only skeptic).

But here’s what’s of concern to a lot of security researchers I deal with:  It was known by McAfee (and certainly others) but no one apparently ever did anything to take the C&C down, even after knowing about it for months.

Let’s take a look at this paragraph from the hyperbolic Vanity Fair article (italics are mine):
"Alperovitch first picked up the trail of Shady rat in early 2009, when a McAfee client, a U.S. defense contractor, identified suspicious programs running on its network. Forensic investigation revealed that the defense contractor had been hit by a species of malware that had never been seen before: a spear-phishing e-mail containing a link to a Web page that, when clicked, automatically loaded a malicious program—a remote-access tool, or rat—onto the victim’s computer. The rat opened the door for a live intruder to get on the network, escalate user privileges, and begin exfiltrating data. After identifying the command-and-control server, located in a Western country, that operated this piece of malware, McAfee blocked its own clients from connecting to that server. Only this March, however, did Alperovitch finally discover the logs stored on the attackers’ servers. This allowed McAfee to identify the victims by name (using their Internet Protocol [I.P.] addresses) and to track the pattern of infections in detail."
So McAfee blocked the IPs for its own customers. In March the C&C was discovered. It’s not clear if it’s still up or finally down (or if it was down by June).

I never saw one mention of this C&C on any of the closed and vetted security lists I’m on.  A simple “takedown please” would have generated all the help necessary.  This is how a lot of bad stuff gets handled, and the vast majority of internet users are none-the-wiser that there is a large group of very dedicated researchers who are making their lives safer every day.  All of the data on the C&C can be put away nicely for post-takedown analysis.

I’m quite certain that McAfee wasn’t the only organization that knew about this, so it’s not only McAfee who shares the blame here. Furthermore, I am not singling out McAfee (we work with them on other areas and there are many very decent people there). Furthermore, McAfee is being clear that this issue is “old news”, and McAfee’s Dmitri Alperovitch is not acting the role of the self-aggrandizer, but rather as a researcher sharing some pretty interesting and educational insights.  Furthermore, McAfee did reach out to infected victims. 

However, there are many groups or organizations, upon having proof of this C&C, that would have been all over shutting the thing down as fast as possible in coordination with other security organizations.

The bigger point is this:  If you, as a security researcher, discover Really Bad Stuff, you should do everything in your power to get that Really Bad Stuff shut down.  The next time you see a killer presentation at Blackhat or RSA, ask “what have you done to solve the problem?”.

Perhaps we need a volutnary code of ethics for the security industry.  It can start with some pretty simple things, like “If I see really bad stuff happening, I will work with others to fix it”.  Enlightened self interest and all that.

Screw NDAs, the fear of competition getting a heads-up on your research, losing a scoopable news story, etc.

This is not about McAfee.  This is about the industry.  There are researchers out there who aren’t in a position to share data with competitors due to corporate reasons.  They shouldn’t be in that position.  

Alex Eckelberry
Reposted fromsec sec

July 30 2011

The One-Time Pad is the first perfectly secure cipher. Its invention is usually credited to Gilbert S. Vernam and Joseph O. Mauborgne. Prof. Steven M. Bellovin from the Department of Computer Science at Columbia University shows that it was known approx. 35 years earlier to a Sacramento banker named Frank Miller. He also published his scheme in the book Telegraphic Code to Insure Privacy and Secrecy in the Transmission of Telegrams. Steven Bellovin rediscovered this book in the Library of Congress. He has published his findings in Steven M. Bellovin: 'Frank Miller: Inventor of the One-Time Pad', Cryptologia, Volume 35, Issue 3, pages 203-222, July 2011.
IACR News Central
Reposted bylit lit

July 26 2011

July 25 2011

Pwnie for Most Epic FAIL

Sometimes giving 110% just makes your FAIL that much more epic. And what use would the Internet be if it wasn't there to document this FAIL for all time?

This award is to honor a person or company's spectacularly epic FAIL. And the nominees are:

  • Sony

    After Fail0verflow and GeoHot published how to jailbreak the PS3, Sony got a bit miffed. Apparently unfamiliar with how the Internet works and how difficult it is to remove the piss from a swimming pool, Sony proceeded to try erase the information from the Internet and sue GeoHot et al. into oblivion. Needless to say, this was about as successful as the MiniDisc.

  • Sony

    Speaking of piss in a swimming pool, that just happened to be how well Sony protected their Sony Online Entertainment (SOE) users' account info and roughly 25 to 77 million account details were stolen by unknown hackers. That metaphor makes just about no sense at all, but you get the point: FAIL.

  • Sony

    Sony is definitely good at one thing: keeping the hits coming and their fans entertained. Oh wait, did we say Sony? We meant LulzSec. I guess that counts as another FAIL for Sony.

  • Sony

    After learning the hard way that their PlayStation Network was about as porous as air, Sony had to shut it down for over two months to rebuild it from scratch. In doing so, they made everyone from your 8-year old cousin to your barber learn about the importance of security. Hooray for us, sorry Sony shareholders.

  • Sony

    Noticing a pattern here? But wait, it gets better. Sony might have been able to better repel the multitude of attacks if they hadn't just recently laid off a significant number of their network security team. Great timing, guys.

Pwnie Awards 2011

Pwnie Award Nominations 2011

once more with some fine hacks, lame vendor responses and also some really nice audio tracks
Reposted byreturn13 return13

July 21 2011

One careless strcat

July 19 2011

Crouching Tiger - Hidden Payload: Security Risks of Scalable Vector Graphics

Scalable Vector Graphics (SVG) images so far played a rather small role on the WWW. This was mainly due to the lack of proper browser support. Recently, things have changed: the W3C and WHATWG draft specifications for HTML5 require modern web browsers to support SVG images to be embedded in a multitude of ways. Now SVG images can be embedded through the classical method via specific tags such as <embed> or <object>, or in novel ways, such as with <img> tags, CSS or inline in any HTML5 document.
SVG files are generally considered to be plain images or animations, and security-wise, they are being treated as such (e.g., when an embedment of local or remote SVG images into websites or uploading these files into rich web applications takes place). Unfortunately, this procedure poses great risks for the web applications and the users utilizing them, as it has been proven that SVG files must be considered fully functional, one-file web applications potentially containing HTML, JavaScript, Flash, and other interactive code structures. We found that even more severe problems have resulted from the often improper handling of complex and maliciously prepared SVG files by the browsers.
In this paper, we provide a detailed overview and discussion of the security risks originating from the improper SVG handling. We introduce several novel attack techniques targeted at major websites, as well as modern browsers, email clients and other comparable tools. We examine and present how current filtering techniques are circumventable by using SVG files and subsequently propose an innovative way to mitigate these risks. The paper showcases our research into the usage of SVG images as attack tools, and determines its impact on state-of-the-art browsers such as Firefox 4, Internet Explorer 9 and Opera 11.

We will present this work at ACM CCS 2011.
Play fullscreen
Skype vulnerability demoed

July 07 2011

July 03 2011

Spammers Hone In on Google+

Our friends at Sophos has found what we consider as, probably, the first crime ever targeting Google+: fake pharma spam. Due to the high demand of G+ invites being thrown at Google, to the point that the company actually had to cease the invitation process for the beta release of their fledgling social networking site, it is no surprise that spammers have latched onto this one as their latest target (and growing favourite?) to date.

Better than having malware there, if you ask me.

That, of course, does not change the fact that receiving supposed G+ invitations leading to fake pharma site is annoying.

"The spammers are no doubt hoping that the email will be too hard to resist for many people eager to see Google's new social network, although just how many users will be tempted to buy drugs online is a mystery." concludes Sophos regarding this report.


Screenshot of the G+ spam from Sophos

Personally, I am a bit jolted by the fact that spammers didn't take long before they push a campaign to take advantage of Internet users badly wanting to be put in circles. It's the current "it" thing, after all. Not to mention the current perfect target of any threat attack, and spamming was the first. I can only guess what could come next after that.

It's a jungle out there, folks. As always, please stay safe. :)

Jovi Umawing
Reposted fromsec sec
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