Schoolhouse Exploits | TechSNAP 296

chris

6 years ago

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Project Zero: Breaking the chain

“Much as we’d like it to be true, it seems undeniable that we’ll never fix all security bugs just by looking for them. One of most productive ways to dealing with this fact is to implement exploit mitigations. Project Zero considers mitigation work just as important as finding vulnerabilities. Sometimes we can get our hands dirty, such as helping out Adobe and Microsoft in Flash mitigations. Sometimes we can only help indirectly via publishing our research and giving vendors an incentive to add their own mitigations.”
“This blog post is about an important exploit mitigation I developed for Chrome on Windows. It will detail many of the challenges I faced when trying to get this mitigation released to protect end-users of Chrome. It’s recently shipped to users of Chrome on Windows 10 (in M54), and ended up blocking the sandbox escape of an exploit chain being used in the wild.”
“It’s possible to lockdown a sandbox such as Chrome’s pretty comprehensively using Restricted Tokens. However one of the big problems on Windows is locking down access to system calls. On Windows you have both the normal NT system calls and Win32k system calls for accessing the GUI which combined represents a significant attack surface.”
“While the NT system calls do have exploitable vulnerabilities now and again (for example issue 865) it’s nothing compared to Win32k. From just one research project alone 31 issues were discovered, and this isn’t counting the many font issues Mateusz has found and the hundreds of other issues found by other researchers.”
“Much of Win32k’s problems come from history. In the first versions of Windows NT almost all the code responsible for the windowing system existed in user-mode. Unfortunately for 90’s era computers this wasn’t exactly good for performance so for NT 4 Microsoft moved a significant portion of what was user-mode code into the kernel (becoming the driver, win32k.sys). This was a time before Slammer, before Blaster, before the infamous Trustworthy Computing Memo which focussed Microsoft to think about security first. Perhaps some lone voice spoke for security that day, but was overwhelmed by performance considerations. We’ll never know for sure, however what it did do was make Win32k a large fragile mess which seems to have persisted to this day. And the attack surface this large fragile mess exposed could not be removed from any sandboxed process.”
“That all changed with the release of Windows 8. Microsoft introduced the System Call Disable Policy, which allows a developer to completely block access to the Win32k system call table. While it doesn’t do anything for normal system calls the fact that you could eliminate over a thousand win32k system calls, many of which have had serious security issues, would be a crucial reduction in the attack surface.”
“However no application in a default Windows installation used this policy (it’s said to have been introduced for non-GUI applications such as on Azure) and using it for something as complex as Chrome wasn’t going to be easy. The process of shipping Win32k lockdown required a number of architectural changes to be made to Chrome. This included replacing the GDI-based font code with Microsoft’s DirectWrite library. After around two years of effort Win32k lockdown was shipping by default.”
The problem is that plugins, like Flash and PDFium, run via the PPAPI, and cannot have access to the Win32k blocked
“This would seem a pretty large weak point. Flash has not had the best security track record (relevant), making the likelihood of Flash being an RCE vector very high. Combine that with the relative ease of finding and exploiting Win32k vulnerabilities and you’ve got a perfect storm.”
“It would seem reasonable to assume that real attackers are finding Win32k vulnerabilities and using them to break out of restrictive sandboxes including Chrome’s using Flash as the RCE vector. The question was whether that was true. The first real confirmation that this was true came from the Hacking Team breach, which occurred in July 2015. In the dumped files was an unfixed Chrome exploit which used Flash as the RCE vector and a Win32k exploit to escape the sandbox. While both vulnerabilities were quickly fixed I came upon the idea that perhaps I could spend some time to implement the lockdown policy for PPAPI and eliminate this entire attack chain.”
“For a better, more robust solution I needed to get changes made to Flash. I don’t have access to the Flash source code, however Google does have a good working relationship with Adobe and I used this to get the necessary changes implemented. It turned out that there was a Pepper API which did all that was needed to replace the GDI font handling, pp::flash::FontFile. Unfortunately that was only implemented on Linux, however I was able to put together a proof-of-concept Windows implementation of pp::flash::FontFile and through Xing Zhang of Adobe we got a full implementation in Chrome and Flash.”
So, with some work, most of the code in Flash that needed access to the Win32k API could be removed, so access to it could be blocked
“From this point I could enable Win32k lockdown for plugins and after much testing everything seemed to be working, until I tried to test some DRM protected video. While encrypted video worked, any Flash video file which required output protection (such as High-bandwidth Digital Content Protection (HDCP)) would not.”
“Still this presents a problem, as video along with games are some of the only residual uses of Flash. In testing, this also affected the Widevine plugin that implements the Encrypted Media Extensions for Chrome. Widevine uses PPAPI under the hood; not fixing this issue would break all HD content playback.”
“The ideal way of fixing this would be to implement a new API in Chrome which exposed enabling HDCP then get Adobe and Widevine to use that implementation. It turns out that the Adobe DRM and Widevine teams are under greater constraints than normal development teams. After discussion with my original contact at Adobe they didn’t have access to the DRM code for Flash. I was able to have meetings with Widevine (they’re part of Google) and the Adobe DRM team but in the end I decided to go it alone and implement redirection of these APIs as part of the sandbox code.”
It seems that the DRM code is so locked down, that even the developers at the companies that created it, cannot modify it
So the Chrome developer just created a compatibility layer, that brokers the Win32k calls to a separate process, that is outside of the Win32k API blocking, so the calls can succeed
“From the first patch submitted in September 2015 to the final patch in June it took almost 10 months of effort to come up with a shipping mitigation. The fact that it’s had its first public success (and who knows how many non-public ones) shows that it was worth implementing this mitigation.”
“In the latest version of Windows 10, Anniversary Edition, Microsoft have implemented a Win32k filter which makes it easier to reduce the attack surface without completely disabling all the system calls which might have sped up development. Microsoft are also taking pro-active effort to improve the Win32k code base.”

‘Avalanche’ Global Fraud Ring Dismantled

“In what’s being billed as an unprecedented global law enforcement response to cybercrime, federal investigators in the United States, United Kingdom and Europe today say they’ve dismantled a sprawling cybercrime machine known as “Avalanche” — a distributed, cloud-hosting network that for the past seven years has been rented out to fraudsters for use in launching countless malware and phishing attacks.”
“The Avalanche network was used as a delivery platform to launch and manage mass global malware attacks and money mule recruiting campaigns. It has caused an estimated EUR 6 million in damages in concentrated cyberattacks on online banking systems in Germany alone. In addition, the monetary losses associated with malware attacks conducted over the Avalanche network are estimated to be in the hundreds of millions of euros worldwide, although exact calculations are difficult due to the high number of malware families managed through the platform.”
“The global effort to take down this network involved the crucial support of prosecutors and investigators from 30 countries. As a result, 5 individuals were arrested, 37 premises were searched, and 39 servers were seized. Victims of malware infections were identified in over 180 countries. Also, 221 servers were put offline through abuse notifications sent to the hosting providers. The operation marks the largest-ever use of sinkholing[1] to combat botnet[2] infrastructures and is unprecedented in its scale, with over 800 000 domains seized, sinkholed or blocked.”
“Built as a criminal cloud-hosting environment that was rented out to scammers, spammers other ne’er-do-wells, Avalanche has been a major source of cybercrime for years. In 2009, when investigators say the fraud network first opened for business, Avalanche was responsible for funneling roughly two-thirds of all phishing attacks aimed at stealing usernames and passwords for bank and e-commerce sites. By 2011, Avalanche was being heavily used by crooks to deploy banking Trojans.”
““Cyber criminals rented the servers and through them launched and managed digital fraud campaigns, sending emails in bulk to infect computers with malware, ransomware and other malicious software that would steal users’ bank details and other personal data,” the NCA said in a statement released today on the takedown. The criminals used the stolen information for fraud or extortion. At its peak 17 different types of malware were hosted by the network, including major strains with names such as goznym, urlzone, pandabanker and loosemailsniffer. At least 500,000 computers around the world were infected and controlled by the Avalanche system on any given day.””
“The Avalanche network was especially resilient because it relied on a hosting method known as fast-flux, a kind of round-robin technique that lets botnets hide phishing and malware delivery sites behind an ever-changing network of compromised systems acting as proxies.”
By constantly changing addresses, it is hard for researchers and others to report the compromised hosts. Even when trying constant lookups, a researcher will only see a fraction of the actual hosts in the network.
“It’s worth noting here that Avalanche has for many years been heavily favored by crime gangs to deploy Zeus and SpyEye malware variants involved in cleaning out bank accounts for a large number of small to mid-sized businesses. These attacks relied heavily on so-called “money mules,” people willingly or unwittingly recruited into helping fraudsters launder stolen funds.”
“The Shadowserver Foundation, a non-profit organization of security professionals that assisted in what the organization described in a post on the takedown as an 18-month collaboration with law enforcement, described Avalanche as a “Double Fast Flux” botnet. Individual nodes within the botnet are registered and then quickly de-registered as the host associated with a Domain Name Service A address record for a single DNS name The destination addresses for a DNS record often change as quickly as once every 5 minutes, and can cycle through hundreds or thousands of IP addresses. And there are multiple domain names for command and control nodes hard-coded into the botnet malware, allowing the bots to switch to a different domain name if a specific domain is blocked.”
Additional Coverage
EuroPol Announcement
EuroPol Technical Infographic

Meet the men who spy on women through their webcams

The article describes some miscreants using RATs (Remote Administration Trojans) to control people’s computers, then using it to harass them and/or spy on them in various ways
It describes a scenario of a ratter watching and taunting a victim. Trying to scare and shock them
“See! That shit keeps popping up on my fucking computer!” says a blond woman as she leans back on a couch, bottle-feeding a baby on her lap.
“The woman is visible from thousands of miles away on a hacker’s computer. The hacker has infected her machine with a remote administration tool (RAT) that gives him access to the woman’s screen, to her webcam, to her files, to her microphone. He watches her and the baby through a small control window open on his Windows PC, then he decides to have a little fun. He enters a series of shock and pornographic websites and watches them appear on the woman’s computer.”
“The woman is startled. “Did it scare you?” she asks someone off camera. A young man steps into the webcam frame. “Yes,” he says. Both stare at the computer in horrified fascination. A picture of old naked men appears in their Web browser, then vanishes as a McAfee security product blocks a “dangerous site.””
“Far away, the hacker opens his “Fun Manager” control panel, which provides a host of tools for messing with his RAT victims. He can hide their Windows “Start” button or the taskbar or the clock or the desktop, badly confusing many casual Windows users. He can have their computer speak to them. Instead, he settles for popping open the remote computer’s optical drive”
“Copies of the incident aren’t hard to find. They’re on YouTube, along with thousands of other videos showing RAT controller (or “ratters,” as they will be called here) taunting, pranking, or toying with victims. But, of course, the kinds of people who watch others through their own webcams aren’t likely to limit themselves to these sorts of mere hijinks—not when computers store and webcams record far more intimate material.”
“”Man I feel dirty looking at these pics,” wrote one forum poster at Hack Forums, one of the top “aboveground” hacking discussion sites on the Internet (it now has more than 23 million total posts). The poster was referencing a 134+ page thread filled with the images of female “slaves” surreptitiously snapped by hackers using the women’s own webcams. “Poor people think they are alone in their private homes, but have no idea they are the laughing stock on HackForums,” he continued. “It would be funny if one of these slaves venture into learning how to hack and comes across this thread.””
“Whether this would in fact be “funny” is unlikely. RAT operators have nearly complete control over the computers they infect; they can (and do) browse people’s private pictures in search of erotic images to share with each other online. They even have strategies for watching where women store the photos most likely to be compromising.”
I have always found people’s storage and organization strategies fascinating, especially for material they are trying to ‘hide in plain sight’
“RAT tools aren’t new; the hacker group Cult of the Dead Cow famously released an early one called BackOrifice at the Defcon hacker convention in 1998. The lead author, who went by the alias Sir Dystic, called BackOrifice a tool designed for “remote tech support aid and employee monitoring and administering [of a Windows network].” But the Cult of the Dead Cow press release made clear that BackOrifice was meant to expose “Microsoft’s Swiss cheese approach to security.” Compared to today’s tools, BackOrifice was primitive. It could handle the basics, though: logging keystrokes, restarting the target machine, transferring files between computers, and snapping screenshots of the target computer.”
“”I seem to get a lot of female slaves by spreading Sims 3 with a [RAT] server on torrent sites,” wrote one poster. Another turned to social media, where “I’ve been able to message random hot girls on facebook (0 mutual friends) and infect (usually become friends with them too); with the right words anything is possible.””
“Calling most of these guys “hackers” does a real disservice to hackers everywhere; only minimal technical skill is now required to deploy a RAT and acquire slaves. Once infected, all the common RAT software provides a control panel view in which one can see all current slaves, their locations, and the status of their machines. With a few clicks, the operator can start watching the screen or webcam of any slave currently online.”
“One of the biggest problems ratters face is the increasing prevalence of webcam lights that indicate when the camera is in use. Entire threads are devoted to bypassing the lights, which routinely worry RAT victims and often lead to the loss of slaves.”
“Unfortunately she asked her boyfriend why the light on her cam kept coming on,” one RAT controller wrote. “And he knew, she never came back :)”
“RATs can be entirely legitimate. Security companies have used them to help find and retrieve stolen laptops, for instance, and no one objects to similar remote login software such as LogMeIn. The developers behind RAT software generally describe their products as nothing more than tools which can be used for good and ill. And yet some tools have features that make them look a lot like they’re built with lawlessness in mind.”
“RATs aren’t going away, despite the occasional intervention of the authorities. Too many exist, plenty of them are entirely legal, and source code is in the wild (a version of the Blackshades source leaked in 2010). Those who don’t want to end up being toyed with in a YouTube video are advised to take the same precautions that apply to most malware: use a solid anti-malware program, keep your operating system updated, and make sure plugins (especially Flash and Java) aren’t out of date. Don’t visit dodgy forums or buy dodgy items, don’t click dodgy attachments in e-mail, and don’t download dodgy torrents. Such steps won’t stop every attack, but they will foil many casual users looking to add a few more slaves to their collections.”
“If you are unlucky enough to have your computer infected with a RAT, prepare to be sold or traded to the kind of person who enters forums to ask, “Can I get some slaves for my rat please? I got 2 bucks lol I will give it to you :b” At that point, the indignities you will suffer—and the horrific website images you may see—will be limited only by the imagination of that most terrifying person: a 14-year-old boy with an unsupervised Internet connection.”
Honestly, this article was rather tame in its list of possibly things the ratters could do to you.
To pay off webcam spies, Detroit kid pawns $100k in family jewels for $1,500

Schoolhouse Exploits | TechSNAP 296

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Become a supporter on Patreon:

Show Notes:

Project Zero: Breaking the chain

‘Avalanche’ Global Fraud Ring Dismantled

Meet the men who spy on women through their webcams

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