Before we delve into the intricacies of individual methods of anti-debugging let’s use this post to define the classes of anti-debugging that we will be discussing. While other classes may exist, the definition of these classes is an attempt to include the majority of anti-debugging methods in use today. There is some overlap between classifications and we may have left out some methods due to limited exposure or effectiveness.

API Based Anti-Debugging
API based anti-debugging is the most straightforward and possibly the easiest to understand for a typical developer. Using both documented and undocumented API calls, these methods query process and system information to determine the existence or operation of a debugger. From single line calls such as IsDebuggerPresent() and CheckRemoteDebugger() to slightly more complex methods including debugger detaching and CloseHandle() checks. These methods are generally trivial to add to an existing code base and many can even be implemented in as few as two or three lines.

Exception Based Anti-Debugging
Exception based anti-debugging is slightly different than your basic API based techniques. Many times when a debugger is attached to a process, exceptions are trapped and handled by the debugger without regard to passing the exception back to the application for continued execution. Occasionally these exceptions can even crash or terminate a process when run under a debugger and be handled gracefully when running clean. It is these discrepancies that makes exception based anti-debugging techniques possible.

Process and Thread Block Anti-Debugging
Some of the API based anti-debugging methods use published functions to query information from within the process and thread blocks for our running code. Many API based detections can be subverted within a debugger by hooking the API call and returning values that indicate a clean process. One way around this subversion is to directly query the process and thread blocks, bypassing the API calls. Direct analysis of the process and thread blocks, while more complex, can lead to a more accurate and high assurance result.

Modified Code Anti-Debugging
One of the methods that a debugger uses to signal a breakpoint is to insert a break byte into the running code at the location that it wishes to stop execution. The process execution breaks when this value is seen, giving control to the debugger. When the program is resumed, the breakpoint value is removed and replaced with the original byte, the execution backed up one byte, and the program is resumed. Detection of software based breakpoints can be achieved by analyzing the process for modifications from the expected norm.

Hardware and Register Based Anti-Debugging
A second way that a debugger can break the execution of a process is by using a hardware breakpoint. A hardware breakpoint relies upon CPU registers to store the pertinent information and to detect when the target break addresses are seen on the bus. A break interrupt is triggered at the appropriate time based on these register values. Reading or modifying the hardware can allow for the detection of a debugger.

Timing and Latency Anti-Debugging
Finally timing and latency can be used as an effective anti-debugging method. When executing a program within a debugger, specifically when single stepping, a much larger latency occurs between execution of instructions. This latency can be detected and compared against a reasonable threshold to detect the existence of a debugger attached to our process.

Each of the classes of anti-debugging outlined above has merit when used individually to protect a process. While none of them can be assured to ever protect a program from a determined reverse engineer or debugger, implementation of these techniques (or many of them if appropriate) can sufficiently slow down the debugging process and hopefully make the attacker spend his time on other, easier, ventures. In the remainder of this series on anti-debugging we will review in depth some of the more interesting methods of each of the above classes. So bring along your debugger and your development environment and let the games begin.

Linksys addressed many of my concerns with that previous device. The 610N can mount a drive and share it via SMB and FTP, have two full-speed connections running over both bands without skipping a beat, and supports several methods of getting the one-click WPS (Wi-Fi Protected Setup) to work. Read the review for all the details, but I can't recommend this router to Mac users with any needs beyond basic networking; I'm perfectly happy to give it a full thumbs-up for Windows XP and Vista users, however.

WPS is a particular mess, by the way. Linksys has four somewhat distinct methods of using WPS to enable a password-free encrypted connection between a client and a base station: a button on the front that, when pressed, turns on WPS; and three modes (one of them similar to that button) accessible via their Web configuration software. One option is to get the base station to create a short PIN that's then entered on the client system as an out-of-band confirmation that there's no man in the middle.

Apple, by contrast, has a single way of joining a WPS-offering base station: it displays the network's name in bold. Select the network, and Mac OS X displays a key code that needs to be entered on the base station. But the WRT610N can't handle that option. If you put the WRT610N into a mode in which Apple can spot the device as offering a WPS handshake, you can't enter the code into the Linksys router!

This shows that there's still rough edges in the WPS protocol that two of the highest-selling makers of Wi-Fi gear can manage to not mesh up their respective options. (Apple declined to comment for my Macworld story; Linksys confirmed the lack of compatibility, but put the burden on Apple's doorstep.)

My favorite talk, as expected, was the Sotirov/Dowd talk on How To Impress Girls With Browser Memory Protection Bypasses. The attack is a conceptually simple, yet completely reliable technique for exploiting vulnerabilities in web browsers. Of course, the media has sensationalized the impact of their findings, but ultimately, this is still significant as far as browser-based exploits are concerned. It’s worth mentioning that part of the technique allowing them to load a .NET DLL at an arbitrary location under Vista was reliant on an implementation bug wherein the OS disables ASLR if the version in the .NET COR header was below a certain value. However, the address space spraying and stack spraying techniques are likely to be extended to other platforms utilizing similar memory protection mechanisms.

As for the girls? I can report first-hand that the ladies at TAO on Wednesday night were hanging on Alex’s every word. They were particularly impressed when he whipped out the laptop for a live demo. Unfortunately, none of the dozen iPhone owners in the immediate vicinity thought to snap a picture (too busy Twittering). Oh well.

I also enjoyed Hovav Shacham’s talk on return-oriented programming. Simply put, he described a generalization of the return-to-libc shellcode approach with the intent to demonstrate that one could achieve Turing-complete computation using “found code” in process images. By chaining together series of mini-computations ending in return (RET) instructions, it was possible to build higher-level programming constructs such as branches and loops. The nature of the x86 instruction set provides some flexibility because instructions are interpreted differently depending on how you align the instruction pointer (i.e. the old shellcode trick of searching the process image for any JMP EBX instruction and using that as your EIP). In RISC architectures such as SPARC, however, you don’t have that luxury; if your %pc isn’t aligned properly you get a bus error. So it was quite interesting to see that they were able to extend the concept to RISC. The practicality of the attack technique is limited by the fact that the shellcode is tuned to a particular binary image — if the shellcode was built using instructions extrapolated from glibc 2.3.5, it won’t work for a system running glibc 2.4.

I thought Scott Stender’s talk on Concurrency Attacks in Web Applications was interesting as well. In a nutshell, spewing thousands of simultaneous requests at web application transactions that are not thread-safe can create interesting problems. In the presentation, Scott ran his demo against a VM running on the attack machine. I found myself wondering how effective the same attack would be over the Internet — would it be significantly less reliable (or not at all)? Race conditions are generally easier to exploit locally than remotely due to more predictable execution conditions. Certainly this is an under-tested vulnerability class though.

One presentation I wasn’t able to attend but want to follow up on is Nate McFeters, John Heasman, and Rob Carter’s talk which discussed the GIFAR attack I’ve been hearing so much about lately. The gist is that you can create a file that is both a valid GIF and a valid JAR, then use some Java applet tricks to initiate HTTP requests on behalf of the victim.

Finally, the Pwnie Awards didn’t fail to disappoint. Drama ensued over the Most Overhyped award, but at least this year some of the winners showed up to claim their awards! Halvar rapping Symantec lyrics was also quite memorable.

All in all, a fun and informative week, but as usual, I was relieved to get the hell out of Vegas and head home on Friday morning.

P.S. For a much more entertaining BlackHat/Defcon Recap, read Jennifer Jabbusch’s account of the week’s events. It’s my favorite one so far!

My favorite talk, as expected, was the Sotirov/Dowd talk on How To Impress Girls With Browser Memory Protection Bypasses. The attack is a conceptually simple, yet completely reliable technique for exploiting vulnerabilities in web browsers. Of course, the media has sensationalized the impact of their findings, but ultimately, this is still significant as far as browser-based exploits are concerned (here is a more accurate report). It’s worth mentioning that part of the technique allowing them to load a .NET DLL at an arbitrary location under Vista was reliant on an implementation bug wherein the OS disables ASLR if the version in the .NET COR header was below a certain value. However, the address space spraying and stack spraying techniques are likely to be extended to other platforms utilizing similar memory protection mechanisms.

As for the girls? I can report first-hand that the ladies at TAO on Wednesday night were hanging on Alex’s every word. They were particularly impressed when he whipped out the laptop for a live demo. Unfortunately, none of the dozen iPhone owners in the immediate vicinity thought to snap a picture (too busy Twittering). Oh well.

I also enjoyed Hovav Shacham’s talk on return-oriented programming. Simply put, he described a generalization of the return-to-libc shellcode approach with the intent to demonstrate that one could achieve Turing-complete computation using “found code” in process images. By chaining together series of mini-computations ending in return (RET) instructions, it was possible to build higher-level programming constructs such as branches and loops. The nature of the x86 instruction set provides some flexibility because instructions are interpreted differently depending on how you align the instruction pointer (i.e. the old shellcode trick of searching the process image for any JMP EBX instruction and using that as your EIP). In RISC architectures such as SPARC, however, you don’t have that luxury; if your %pc isn’t aligned properly you get a bus error. So it was quite interesting to see that they were able to extend the concept to RISC. The practicality of the attack technique is limited by the fact that the shellcode is tuned to a particular binary image — if the shellcode was built using instructions extrapolated from glibc 2.3.5, it won’t work for a system running glibc 2.4.

I thought Scott Stender’s talk on Concurrency Attacks in Web Applications was interesting as well. In a nutshell, spewing thousands of simultaneous requests at web application transactions that are not thread-safe can create interesting problems. In the presentation, Scott ran his demo against a VM running on the attack machine. I found myself wondering how effective the same attack would be over the Internet — would it be significantly less reliable (or not at all)? Race conditions are generally easier to exploit locally than remotely due to more predictable execution conditions. Certainly this is an under-tested vulnerability class though.

One presentation I wasn’t able to attend but want to follow up on is Nate McFeters, John Heasman, and Rob Carter’s talk which discussed the GIFAR attack I’ve been hearing so much about lately. The gist is that you can create a file that is both a valid GIF and a valid JAR, then use some Java applet tricks to initiate HTTP requests on behalf of the victim.

Finally, the Pwnie Awards didn’t fail to disappoint. Drama ensued over the Most Overhyped award, but at least this year some of the winners showed up to claim their awards! Halvar rapping Symantec lyrics was also quite memorable.

All in all, a fun and informative week, but as usual, I was relieved to get the hell out of Vegas and head home on Friday morning.

P.S. For a much more entertaining BlackHat/Defcon Recap, read Jennifer Jabbusch’s account of the week’s events. It’s my favorite one so far!

Buying a lemon is always a bad thing – but when you pay $1 billion for it?! Back in 2005, Google bought a 5% stake in AOL for $1 billion and now is calling that investment “impaired”. That’s one way of putting it, so it’s a good thing Google has money to burn.

At LinuxWorld this week, Bob Sutor, VP of open source and standards at IBM, said that the next 10 years is “do or die” for open source software designed for specific industries. 10 years? That’s like 70 years in open source development time.

And finally…8/8/08…the Olympics are here! Network administrators around the world, except for Terry Childs, will be eyeing office network bandwidth closely as people go online to watch streaming video of the games. NBC and Microsoft will offer 2,200 hours of live video coverage with up to 20 simultaneous live streams of different events. Plus NBCOlympics.com will offer 3,000 hours of on-demand video content. The time difference means that much of the primetime events will be broadcast while the Western hemisphere is supposed to be hard at work. Me – I’m just glad it’s the weekend, and I can get the Olympics fix I’ve been waiting years for.

Ozmo apparently is trying to leverage the ubiquity of Wi-Fi, the market reach of Intel (which has invested in the firm and is pushing its technology), and the dissatisfaction with Bluetooth device association and throughput to stick a wedge into Bluetooth's market domination. Well over a billion Bluetooth chipsets have shipped--CSR alone has shipped over a billion--and estimates put half a billion this year into cell phones alone. So there's a large embedded market to overcome.

This new technology, so far unnamed but apparently part of Intel's Cliffside research program, is trying to reduce complexity by reducing the number of standards needed to drive a computer, while increasing the flexibility of those standards. Ozmo and Intel's system would, for instance, allow a simultaneous WLAN connection and a PAN network of up to 8 devices using a single radio on a computer.

The press releases and articles make it quite unclear whether a new Wi-Fi chip would be needed; that chip would almost certainly not conform to today's Wi-Fi standards except in a compatibility mode, given that Wi-Fi has no capacity for PAN-style connections. Ad hoc mode isn't quite the same thing. In the past, extensions to the 802.11 standards that are the basis of the Wi-Fi certification and service mark were allowed as long as basic 802.11 worked as expected.

Bluetooth and Wi-Fi have been complementary technologies for several years. There were early conflicts--I wrote an article about the severe problems in using Bluetooth 1.1 and 802.11b back in 2001! But those interference and coordination issues were resolved, and Blueooth and Wi-Fi marched forward hand in hand, without any close association between the two trade groups behind the standards and branding, but with a lot of technology acquisitions and mergers on the part of companies that make Wi-Fi gear.

The Bluetooth SIG has been working for years to put Bluetooth on top of ultrawideband (UWB), which is still not readily available in the marketplace. UWB is always next year's big technology, and may be passed by except for applications like high-definition video streaming among a/v electronics. The SIG also announced support in Oct. 2007 for Bluetooth + 802.11, where a Bluetooth device could initiate high-speed transfers using 802.11 (yes, Wi-Fi, but not by that name; no partnership there). Bluetooth plus UWB is likely not available until 2009 at this point; BT and Wi-Fi, not until perhaps 2010. (See my article, "Bluetooth to Add Wi-Fi with UWB Delays in Mind," 2007-10-31.)

It's hard to see how Ozmo builds a place in this infrastructure, even with higher bandwidth, and what Ozmo says is lower power use and a lower cost for their chips, because laptop and desktop makers will need to buy into the Intel/Ozmo ecosystem. The demand for this kind of technology is typically driven by users who buy one component and need their computer to interface with it.

With Ozmo and Intel apparently planning to debut the Wi-Fi chips and driver support next year, it seems like a multi-year process to figure out whether Ozmo can evolve a competitive position to Bluetooth, even as Bluetooth is estimated to be embedded in over 1.2b cell phones by 2012.

Cablevision's already started its rollout: An observant tri-stater at the Cable Rant site spotted Cablevision installers putting up BelAir gear on their cable line. He took some photos.