|Informative Information for the Uninformed|
Real-time Steganography with RTP
Real-time Transfer Protocol (RTP) is used by nearly all Voice-over-IP systems to provide the audio channel for calls. As such, it provides ample opportunity for the creation of a covert communication channel due to its very nature. While use of steganographic techniques with various audio cover-medium has been extensively researched, most applications of such have been limited to audio cover-medium of a static nature such as WAV or MP3 file audio data. This paper details a common technique for the use of steganography with audio data cover-medium, outlines the problem issues that arise when attempting to use such techniques to establish a full-duplex communications channel within audio data transmitted via an unreliable streaming protocol, and documents solutions to these problems. An implementation of the ideas discussed entitled SteganRTP is included in the reference materials.
Engineering in Reverse
Introduction to Reverse Engineering Win32 Applications
During the course of this paper the reader will be (re)introduced to many concepts and tools essential to understanding and controlling native Win32 applications through the eyes of Windows Debugger (WinDBG). Throughout, WinMine will be utilized as a vehicle to deliver and demonstrate the functionality provided by WinDBG and how this functionality can be harnessed to aid the reader in reverse engineering native Win32 applications. Topics covered include an introductory look at IA-32 assembly, register significance, memory protection, stack usage, various WinDBG commands, call stacks, endianness, and portions of the Windows API. Knowledge gleaned will be used to develop an application designed to reveal and/or remove bombs from the WinMine playing grid.
Inside Blizzard: Battle.net
This paper intends to describe a variety of the problems Blizzard Entertainment has encountered from a practical standpoint through their implementation of the large-scale online game matchmaking and chat service, Battle.net. The paper provides some background historical information into the design and purpose of Battle.net and continues on to discuss a variety of flaws that have been observed in the implementation of the system. Readers should come away with a better understanding of problems that can be easily introduced in designing a matchmaking/chat system to operate on such a large scale in addition to some of the serious security-related consequences of not performing proper parameter validation of untrusted clients.
Bypassing PatchGuard on Windows x64
The version of the Windows kernel that runs on the x64 platform has introduced a new feature, nicknamed PatchGuard, that is intended to prevent both malicious software and third-party vendors from modifying certain critical operating system structures. These structures include things like specific system images, the SSDT, the IDT, the GDT, and certain critical processor MSRs. This feature is intended to ensure kernel stability by preventing uncondoned behavior, such as hooking. However, it also has the side effect of preventing legitimate products from working properly. For that reason, this paper will serve as an in-depth analysis of PatchGuard's inner workings with an eye toward techniques that can be used to bypass it. Possible solutions will also be proposed for the bypass techniques that are suggested.
Subverting PatchGuard Version 2
Windows Vista x64 and recently hotfixed versions of the Windows Server 2003 x64 kernel contain an updated version of Microsoft's kernel-mode patch prevention technology known as PatchGuard. This new version of PatchGuard improves on the previous version in several ways, primarily dealing with attempts to increase the difficulty of bypassing PatchGuard from the perspective of an independent software vendor (ISV) deploying a driver that patches the kernel. The feature-set of PatchGuard version 2 is otherwise quite similar to PatchGuard version 1; the SSDT, IDT/GDT, various MSRs, and several kernel global function pointer variables (as well as kernel code) are guarded against unauthorized modification. This paper proposes several methods that can be used to bypass PatchGuard version 2 completely. Potential solutions to these bypass techniques are also suggested. Additionally, this paper describes a mechanism by which PatchGuard version 2 can be subverted to run custom code in place of PatchGuard's system integrity checking code, all while leaving no traces of any kernel patching or custom kernel drivers loaded in the system after PatchGuard has been subverted. This is particularly interesting from the perspective of using PatchGuard's defenses to hide kernel mode code, a goal that is (in many respects) completely contrary to what PatchGuard is designed to do.
PatchGuard Reloaded: A Brief Analysis of PatchGuard Version 3
Since the publication of previous bypass or circumvention techniques for Kernel Patch Protection (otherwise known as "PatchGuard"), Microsoft has continued to refine their patch protection system in an attempt to foil known bypass mechanisms. With the release of Windows Server 2008 Beta 3, and later a full-blown distribution of PatchGuard to Windows Vista and Windows Server 2003 via Windows Update, Microsoft has introduced the next generation of PatchGuard to the general public ("PatchGuard 3"). As with previous updates to PatchGuard, version three represents a set of incremental changes that are designed to address perceived weaknesses and known bypass vectors in earlier versions. Additionally, PatchGuard 3 expands the set of kernel variables that are protected from unauthorized modification, eliminating several mechanisms that might be used to circumvent PatchGuard while co-existing (as opposed to disabling) it. This article describes some of the changes that have been made in PatchGuard 3. This article also proposes several new techniques that can be used to circumvent PatchGuard's defenses. Countermeasures for these techniques are also discussed.
Improving Automated Analysis of Windows x64 Binaries
As Windows x64 becomes a more prominent platform, it will become necessary to develop techniques that improve the binary analysis process. In particular, automated techniques that can be performed prior to doing code or data flow analysis can be useful in getting a better understanding for how a binary operates. To that point, this paper gives a brief explanation of some of the changes that have been made to support Windows x64 binaries. From there, a few basic techniques are illustrated that can be used to improve the process of identifying functions, annotating their stack frames, and describing their exception handler relationships. Source code to an example IDA plugin is also included that shows how these techniques can be implemented.
Locreate: An Anagram for Relocate
This paper presents a proof of concept executable packer that does not use any custom code to unpack binaries at execution time. This is different from typical packers which generally rely on packed executables containing code that is used to perform the inverse of the packing operation at runtime. Instead of depending on custom code, the technique described in this paper uses documented behavior of the dynamic loader as a mechanism for performing the unpacking operation. This difference can make binaries packed using this technique more difficult to signature and analyze, but only when presented to an untrained eye. The description of this technique is meant to be an example of a fun thought exercise and not as some sort of revolutionary packer. In fact, it's been used in the virus world many years prior to this paper.
An Objective Analysis of the Lockdown Protection System for Battle.net
Near the end of 2006, Blizzard deployed the first major update to the version check and client software authentication system used to verify the authenticity of clients connecting to Battle.net using the binary game client protocol. This system had been in use since just after the release of the original Diablo game and the public launch of Battle.net. The new authentication module (Lockdown) introduced a variety of mechanisms designed to raise the bar with respect to spoofing a game client when logging on to Battle.net. In addition, the new authentication module also introduced run-time integrity checks of client binaries in memory. This is meant to provide simple detection of many client modifications (often labeled "hacks") that patch game code in-memory in order to modify game behavior. The Lockdown authentication module also introduced some anti-debugging techniques that are designed to make it more difficult to reverse engineer the module. In addition, several checks that are designed to make it difficult to simply load and run the Blizzard Lockdown module from the context of an unauthorized, non-Blizzard-game process. After all, if an attacker can simply load and run the Lockdown module in his or her own process, it becomes trivially easy to spoof the game client logon process, or to allow a modified game client to log on to Battle.net successfully. However, like any protection mechanism, the new Lockdown module is not without its flaws, some of which are discussed in detail in this paper.
Using dual-mappings to evade automated unpackers
Automated unpackers such as Renovo, Saffron, and Pandora's Bochs attempt to dynamically unpack executables by detecting the execution of code from regions of virtual memory that have been written to. While this is an elegant method of detecting dynamic code execution, it is possible to evade these unpackers by dual-mapping physical pages to two distinct virtual address regions where one region is used as an editable mapping and the second region is used as an executable mapping. In this way, the editable mapping is written to during the unpacking process and the executable mapping is used to execute the unpacked code dynamically. This effectively evades automated unpackers which rely on detecting the execution of code from virtual addresses that have been written to.
Can you find me now? Unlocking the Verizon Wireless xv6800 (HTC Titan) GPS
In August 2008 Verizon Wireless released a firmware upgrade for their xv6800 (rebranded HTC Titan) line of Windows Mobile smartphones that provided a number of new features previously unavailable on the device on the initial release firmware. In particular, support for accessing the device's built-in Qualcomm gpsOne assisted GPS chipset was introduced with this update. However, Verizon Wireless elected to attempt to lock down the GPS hardware on xv6800 such that only applications authorized by Verizon Wireless would be able to access the device's built-in GPS hardware and perform location-based functions (such as GPS-assisted navigation). The mechanism used to lock down the GPS hardware is entirely client-side based, however, and as such suffers from fundamental limitations in terms of how effective the lockdown can be in the face of an almost fully user-programmable Windows Mobile-based device. This article outlines the basic philosophy used to prevent unauthorized applications from accessing the GPS hardware and provides a discussion of several of the flaws inherent in the chosen design of the protection mechanism. In addition, several pitfalls relating to debugging and reverse engineering programs on Windows Mobile are also discussed. Finally, several suggested design alterations that would have mitigated some of the flaws in the current GPS lock down system from the perspective of safeguarding the privacy of user location data are also presented.
Post-Exploitation on Windows using ActiveX Controls
When exploiting software vulnerabilities it is sometimes impossible to build direct communication channels between a target machine and an attacker's machine due to restrictive outbound filters that may be in place on the target machine's network. Bypassing these filters involves creating a post-exploitation payload that is capable of masquerading as normal user traffic from within the context of a trusted process. One method of accomplishing this is to create a payload that enables ActiveX controls by modifying Internet Explorer's zone restrictions. With ActiveX controls enabled, the payload can then launch a hidden instance of Internet Explorer that is pointed at a URL with an embedded ActiveX control. The end result is the ability for an attacker to run custom code in the form of a DLL on a target machine by using a trusted process that uses one or more trusted communication protocols, such as HTTP or DNS.
Temporal Return Addresses
Nearly all existing exploitation vectors depend on some knowledge of a process' address space prior to an attack in order to gain meaningful control of execution flow. In cases where this is necessary, exploit authors generally make use of static addresses that may or may not be portable between various operating system and application revisions. This fact can make exploits unreliable depending on how well researched the static addresses were at the time that the exploit was implemented. In some cases, though, it may be possible to predict and make use of certain addresses in memory that do not have static contents. This document introduces the concept of temporal addresses and describes how they can be used, under certain circumstances, to make exploitation more reliable.
Bypassing Windows Hardware-enforced DEP
This paper describes a technique that can be used to bypass Windows hardware-enforced Data Execution Prevention (DEP) on default installations of Windows XP Service Pack 2 and Windows 2003 Server Service Pack 1. This technique makes it possible to execute code from regions that are typically non-executable when hardware support is present, such as thread stacks and process heaps. While other techniques have been used to accomplish similar feats, such as returning into NtProtectVirtualMemory, this approach requires no direct reprotecting of memory regions, no copying of arbitrary code to other locations, and does not have issues with NULL bytes. The result is a feasible approach that can be used to easily bypass the enhancements offered by hardware-enforced DEP on Windows in a way that requires very minimal modifications to existing exploits.
Windows Kernel-mode Payload Fundamentals
This paper discusses the theoretical and practical implementations of kernel-mode payloads on Windows. At the time of this writing, kernel-mode research is generally regarded as the realm of a few, but it is hoped that documents such as this one will encourage a thoughtful progression of the subject matter. To that point, this paper will describe some of the general techniques and algorithms that may be useful when implementing kernel-mode payloads. Furthermore, the anatomy of a kernel-mode payload will be broken down into four distinct units, known as payload components, and explained in detail. In the end, the reader should walk away with a concrete understanding of the way in which kernel-mode payloads operate on Windows.
Exploiting the Otherwise Non-Exploitable on Windows
This paper describes a technique that can be applied in certain situations to gain arbitrary code execution through software bugs that would not otherwise be exploitable, such as NULL pointer dereferences. To facilitate this, an attacker gains control of the top-level unhandled exception filter for a process in an indirect fashion. While there has been previous work illustrating the usefulness in gaining control of the top-level unhandled exception filter, Microsoft has taken steps in XPSP2 and beyond, such as function pointer encoding, to prevent attackers from being able to overwrite and control the unhandled exception filter directly. While this security enhancement is a marked improvement, it is still possible for an attacker to gain control of the top-level unhandled exception filter by taking advantage of a design flaw in the way unhandled exception filters are chained. This approach, however, is limited by an attacker's ability to control the chaining of unhandled exception filters, such as through the loading and unloading of DLLs. This does reduce the global impact of this approach; however, there are some interesting cases where it can be immediately applied, such as with Internet Explorer.
Preventing the Exploitation of SEH Overwrites
This paper proposes a technique that can be used to prevent the exploitation of SEH overwrites on 32-bit Windows applications without requiring any recompilation. While Microsoft has attempted to address this attack vector through changes to the exception dispatcher and through enhanced compiler support, such as with /SAFESEH and /GS, the majority of benefits they offer are limited to image files that have been compiled to make use of the compiler enhancements. This limitation means that without all image files being compiled with these enhancements, it may still be possible to leverage an SEH overwrite to gain code execution. In particular, many third-party applications are still vulnerable to SEH overwrites even on the latest versions of Windows because they have not been recompiled to incorporate these enhancements. To that point, the technique described in this paper does not rely on any compile time support and instead can be applied at runtime to existing applications without any noticeable performance degradation. This technique is also backward compatible with all versions of Windows NT+, thus making it a viable and proactive solution for legacy installations.
Implementing a Custom X86 Encoder
This paper describes the process of implementing a custom encoder for the x86 architecture. To help set the stage, the McAfee Subscription Manager ActiveX control vulnerability, which was discovered by eEye, will be used as an example of a vulnerability that requires the implementation of a custom encoder. In particular, this vulnerability does not permit the use of uppercase characters. To help make things more interesting, the encoder described in this paper will also avoid all characters above 0x7f. This will make the encoder both UTF-8 safe and tolower safe.
Exploiting 802.11 Wireless Driver Vulnerabilities on Windows
This paper describes the process of identifying and exploiting 802.11 wireless device driver vulnerabilities on Windows. This process is described in terms of two steps: pre-exploitation and exploitation. The pre-exploitation step provides a basic introduction to the 802.11 protocol along with a description of the tools and libraries the authors used to create a basic 802.11 protocol fuzzer. The exploitation step describes the common elements of an 802.11 wireless device driver exploit. These elements include things like the underlying payload architecture that is used when executing arbitrary code in kernel-mode on Windows, how this payload architecture has been integrated into the 3.0 version of the Metasploit Framework, and the interface that the Metasploit Framework exposes to make developing 802.11 wireless device driver exploits easy. Finally, three separate real world wireless device driver vulnerabilities are used as case studies to illustrate the application of this process. It is hoped that the description and illustration of this process can be used to show that kernel-mode vulnerabilities can be just as dangerous and just as easy to exploit as user-mode vulnerabilities. In so doing, awareness of the need for more robust kernel-mode exploit prevention technology can be raised.
Reducing the Effective Entropy of GS Cookies
This paper describes a technique that can be used to reduce the effective entropy in a given GS cookie by roughly 15 bits. This reduction is made possible because GS uses a number of weak entropy sources that can, with varying degrees of accuracy, be calculated by an attacker. It is important to note, however, that the ability to calculate the values of these sources for an arbitrary cookie currently relies on an attacker having local access to the machine, such as through the local console or through terminal services. This effectively limits the use of this technique to stack-based local privilege escalation vulnerabilities. In addition to the general entropy reduction technique, this paper discusses the amount of effective entropy that exists in services that automatically start during system boot. It is hypothesized that these services may have more predictable states of entropy due to the relative consistency of the boot process. While the techniques described in this paper do not illustrate a complete break of GS, any inherent weakness can have disastrous consequences given that GS is a static, compile-time security solution. It is not possible to simply distribute a patch. Instead, applications must be recompiled to take advantage of any security improvements. In that vein, the paper proposes some solutions that could be applied to address the problems that are outlined.
OS X Kernel-mode Exploitation in a Weekend
Apple's Mac OS X operating system is attracting more attention from users and security researchers alike. Despite this increased interest, there is still an apparent lack of detailed vulnerability development information for OS X. This paper will attempt to help bridge this gap by walking through the entire vulnerability development process. This process starts with vulnerability discovery and ultimately finished with a remote code execution. To help illustrate this process, a real vulnerability found in the OS X wireless device driver is used.
Getting out of Jail: Escaping Internet Explorer Protected Mode
With the introduction of Windows Vista, Microsoft has added a new form of mandatory access control to the core operating system. Internally known as "integrity levels", this new addition to the security manager allows security controls to be placed on a per-process basis. This is different from the traditional model of per-user security controls used in all prior versions of Windows NT. In this manner, integrity levels are essentially a bolt-on to the existing Windows NT security architecture. While the idea is theoretically sound, there does exist a great possibility for implementation errors with respect to how integrity levels work in practice. Integrity levels are the core of Internet Explorer Protected Mode, a new "low-rights" mode where Internet Explorer runs without permission to modify most files or registry keys. This places both Internet Explorer and integrity levels as a whole at the forefront of the computer security battle with respect to Windows Vista.
ActiveX - Active Exploitation
This paper provides a general introduction to the topic of understanding security vulnerabilities that affect ActiveX controls. A brief description of how ActiveX controls are exposed to Internet Explorer is given along with an analysis of three example ActiveX vulnerabilities that have been previously disclosed.
Context-keyed Payload Encoding
A common goal of payload encoders is to evade a third-party detection mechanism which is actively observing attack traffic somewhere along the route from an attacker to their target, filtering on commonly used payload instructions. The use of a payload encoder may be easily detected and blocked as well as opening up the opportunity for the payload to be decoded for further analysis. Even so-called keyed encoders utilize easily observable, recoverable, or guessable key values in their encoding algorithm, thus making decoding on-the-fly trivial once the encoding algorithm is identified. It is feasible that an active observer may make use of the inherent functionality of the decoder stub to decode the payload of a suspected exploit in order to inspect the contents of that payload and make a control decision about the network traffic. This paper presents a new method of keying an encoder which is based entirely on contextual information that is predictable or known about the target by the attacker and constructible or recoverable by the decoder stub when executed at the target. An active observer of the attack traffic however should be unable to decode the payload due to lack of the contextual keying information.
Improving Software Security Analysis using Exploitation Properties
Reliable exploitation of software vulnerabilities has continued to become more difficult as formidable mitigations have been established and are now included by default with most modern operating systems. Future exploitation of software vulnerabilities will rely on either discovering ways to circumvent these mitigations or uncovering flaws that are not adequately protected. Since the majority of the mitigations that exist today lack universal bypass techniques, it has become more fruitful to take the latter approach. It is in this vein that this paper introduces the concept of exploitation properties and describes how they can be used to better understand the exploitability of a system irrespective of a particular vulnerability. Perceived exploitability is of utmost importance to both an attacker and to a defender given the presence of modern mitigations. The ANI vulnerability (MS07-017) is used to help illustrate these points by acting as a simple example of a vulnerability that may have been more easily identified as code that should have received additional scrutiny by taking exploitation properties into consideration.
Analyzing local privilege escalations in win32k
This paper analyzes three vulnerabilities that were found in win32k.sys that allow kernel-mode code execution. The win32k.sys driver is a major component of the GUI subsystem in the Windows operating system. These vulnerabilities have been reported by the author and patched in MS08-025. The first vulnerability is a kernel pool overflow with an old communication mechanism called the Dynamic Data Exchange (DDE) protocol. The second vulnerability involves improper use of the ProbeForWrite function within string management functions. The third vulnerability concerns how win32k handles system menu functions. Their discovery and exploitation are covered.
Exploiting Tomorrow's Internet Today: Penetration testing with IPv6
This paper illustrates how IPv6-enabled systems with link-local and auto-configured addresses can be compromised using existing security tools. While most of the techniques described can apply to "real" IPv6 networks, the focus of this paper is to target IPv6-enabled systems on the local network.
Analyzing Common Binary Parser Mistakes
With just about one file format bug being consistently released on a weekly basis over the past six to twelve months, one can only hope developers would look and learn. The reality of it all is unfortunate; no one cares enough. These bugs have been around for some time now, but have only recently gained media attention due to the large number of vulnerabilities being released. Researchers have been finding more elaborate and passive attack vectors for these bugs, some of which can even leverage a remote compromise.
Effective Bug Discovery
Sophisticated methods are currently being developed and implemented for mitigating the risk of exploitable bugs. The process of researching and discovering vulnerabilities in modern code will require changes to accommodate the shift in vulnerability mitigations. Code coverage analysis implemented in conjunction with fuzz testing reveals faults within a binary file that would have otherwise remained undiscovered by either method alone. This paper suggests a research method for more effective runtime binary analysis using the aforementioned strategy. This study presents empirical evidence that despite the fact that bug detection will become increasingly difficult in the future, analysis techniques have an opportunity to evolve intelligently.
Smart Parking Meters
Security through obscurity is unfortunately much more common than people think: many interfaces are built on the premise that since they are a "closed system" they can ignore standard security practices. This paper will demonstrate how parking meter smart cards implement their protocol and will point out some weaknesses in their design that open the doors to the system. It will also present schematics and code that you can use to perform these basic techniques for auditing almost any type of blackblox secure memory card.
802.11 VLANs and Association Redirection
The goal of this paper is to introduce the reader to a technique that could be used to implement something analogous to VLANs found in wired media into a typical IEEE 802.11 environment. What makes this technique interesting is that it can be accomplished without breaking the IEEE 802.11 standard on the client side, and requires only minor changes made to the Access Point (AP). No modifications are made to the 802.11 MAC. It is the author's hope that after reading the paper the reader will not only understand the specific technique outlined below, but will consider protocol specifications with a new perspective in the future.
Attacking NTLM with Precomputed Hashtables
Breaking encrypted passwords has been of interest to hackers for a long time, and protecting them has always been one of the biggest security problems operating systems have faced, with Microsoft's Windows being no exception. Due to errors in the design of the password encryption scheme, especially in the LanMan(LM) scheme, Windows has a bad track in this field of information security. Especially in the last couple of years, where the outdated DES encryption algorithm that LanMan is based on faced more and more processing power in the average household, combined with ever increasing harddisk size, made it crystal clear that LanMan nowadays is not just outdated, but even antiquated.
Linux Improvised Userland Scheduler Virus
This paper discusses the combination of a userland scheduler and runtime process infection for a virus. These two concepts complete each other. The runtime process infection opens the door to invading into other processes, and the userland scheduler provides a way to make the injected code coexist with the original process code. This allows the virus to remain stealthy and active inside an infected process.
Abusing Mach on Mac OS X
This paper discusses the security implications of Mach being integrated with the Mac OS X kernel. A few examples are used to illustrate how Mach support can be used to bypass some of the BSD security features, such as securelevel. Furthermore, examples are given that show how Mach functions can be used to supplement the limited ptrace functionality included in Mac OS X.
In this paper I will uncover the information exchange of what may be classified as one of the highest money making schemes coordinated by 'organized crime'. I will elaborate on information gathered from a third party individual directly involved in all aspects of the scheme at play. I will provide a detailed explanation of this market's origin, followed by a brief description of some of the actions strategically performed by these individuals in order to ensure their success. Finally, I will elaborate on real world examples of how a single person can be labeled a spammer, malware author, cracker, and an entrepreneur gone thief. For the purposes of avoiding any legal matters, and unwanted media, I will refrain from mentioning the names of any individuals and corporations who are involved in the schemes described in this paper.
Memalyze: Dynamic Analysis of Memory Access Behavior in Software
This paper describes strategies for dynamically analyzing an application's memory access behavior. These strategies make it possible to detect when a read or write is about to occur at a given location in memory while an application is executing. An application's memory access behavior can provide additional insight into its behavior. For example, it may be able to provide an idea of how data propagates throughout the address space. Three individual strategies which can be used to intercept memory accesses are described in this paper. Each strategy makes use of a unique method of intercepting memory accesses. These methods include the use of Dynamic Binary Instrumentation (DBI), x86 hardware paging features, and x86 segmentation features. A detailed description of the design and implementation of these strategies for 32-bit versions of Windows is given. Potential uses for these analysis techniques are described in detail.
Mnemonic Password Formulas
The current information technology landscape is cluttered with a large number of information systems that each have their own individual authentication schemes. Even with single sign-on and multi-system authentication methods, systems within disparate management domains are likely to be utilized by users of various levels of involvement within the landscape as a whole. Due to this complexity and the abundance of authentication requirements, many users are required to manage numerous credentials across various systems. This has given rise to many different insecurities relating to the selection and management of passwords. This paper details a subset of issues facing users and managers of authentication systems involving passwords, discusses current approaches to mitigating those issues, and finally introduces a new method for password management and recalls termed Mnemonic Password Formulas.
During the course of this paper the reader will gain new knowledge about previous and new research on the subject of loop detection. The topic of loop detection will be applied to the field of binary analysis and a case study will be given to illustrate its uses. All of the implementations provided in this document have been written in C/C++ using Interactive Disassembler (IDA) plug-ins.
Social Zombies: Aspects of Trojan Networks
Malicious code is so common in today's Internet that it seems impossible for an average user to keep his or her system clean. It's estimated that several hundred thousand machines are infected by trojans to be abused in a variety of ways, including the theft of money and confidential data as well as extortion, spam, and a whole plethora of further ways. Most often the infected hosts are linked into simple botnets to provide an easy way for the botnet manager to command his zombie army. This article describes ways to form far more effective networks than the ones in use today by the means of stealth, deception, and cryptography.
Mac OS X PPC Shellcode Tricks
Developing shellcode for Mac OS X is not particularly difficult, but there are a number of tips and techniques that can make the process easier and more effective. The independent data and instruction caches of the PowerPC processor can cause a variety of problems with exploit and shellcode development. The common practice of patching opcodes at run-time is much more involved when the instruction cache is in incoherent mode. NULL-free shellcode can be improved by taking advantage of index registers and the reserved bits found in many opcodes, saving space otherwise taken by standard NULL evasion techniques. The Mac OS X operating system introduces a few challenges to unsuspecting developers; system calls change their return address based on whether they succeed and oddities in the Darwin kernel can prevent standard execve() shellcode from working properly with a threaded process. The virtual memory layout on Mac OS X can be abused to overcome instruction cache obstacles and develop even smaller shellcode.
Since the introduction of FU, the rootkit world has moved away from implementing system hooks to hide their presence. Because of this change in offense, a new defense had to be developed. The new algorithms used by rootkit detectors, such as BlackLight, attempt to find what the rootkit is hiding instead of simply detecting the presence of the rootkit's hooks. This paper will discuss an algorithm that is used by both Blacklight and IceSword to detect hidden processes. This paper will also document current weaknesses in the rootkit detection field and introduce a more complete stealth technique implemented as a prototype in FUTo.
GREPEXEC: Grepping Executive Objects from Pool Memory
As rootkits continue to evolve and become more advanced, methods that can be used to detect hidden objects must also evolve. For example, relying on system provided APIs to enumerate maintained lists is no longer enough to provide effective cross-view detection. To that point, scanning virtual memory for object signatures has been shown to provide useful, but limited, results. The following paper outlines the theory and practice behind scanning memory for hidden objects. This method relies upon the ability to safely reference the Windows system virtual address space and also depends upon building and locating effective memory signatures. Using this method as a base, suggestions are made as to what actions might be performed once objects are detected. The paper also provides a simple example of how object-independent signatures can be built and used to detect several different kernel objects on all versions of Windows NT+. Due to time constraints, the source code associated with this paper will be made publicly available in the near future.
A Catalog of Windows Local Kernel-mode Backdoors
This paper presents a detailed catalog of techniques that can be used to create local kernel-mode backdoors on Windows. These techniques include function trampolines, descriptor table hooks, model-specific register hooks, page table modifications, as well as others that have not previously been described. The majority of these techniques have been publicly known far in advance of this paper. However, at the time of this writing, there appears to be no detailed single point of reference for many of them. The intention of this paper is to provide a solid understanding on the subject of local kernel-mode backdoors. This understanding is necessary in order to encourage the thoughtful discussion of potential countermeasures and perceived advancements. In the vein of countermeasures, some additional thoughts are given to the common misconception that PatchGuard, in its current design, can be used to prevent kernel-mode rootkits.
Generalizing Data Flow Information
Generalizing information is a common method of reducing the quantity of data that must be considered during analysis. This fact has been plainly illustrated in relation to static data flow analysis where previous research has described algorithms that can be used to generalize data flow information. These generalizations have helped support more optimal data flow analysis in certain situations. In the same vein, this paper describes a process that can be employed to generalize and persist data flow information along multiple generalization tiers. Each generalization tier is meant to describe the data flow behaviors of a conceptual software element such as an instruction, a basic block, a procedure, a data type, and so on. This process makes use of algorithms described in previous literature to support the generalization of data flow information. To illustrate the usefulness of the generalization process, this paper also presents an algorithm that can be used to determine reachability at each generalization tier. The algorithm determines reachability starting from the least specific generalization tier and uses the set of reachable paths found to progressively qualify data flow information for each successive generalization tier. This helps to constrain the amount of data flow information that must be considered to a minimal subset.
What Were They Thinking?
Annoyances Caused by Unsafe Assumptions
This installation of What Were They Thinking illustrates some of the annoyances that can be caused when developing software that has to inter-operate with third-party applications. Two such cases will be dissected and discussed in detail for the purpose of showing how third-party applications can fail when used in conjunction with software that performs certain tasks. The analysis of the two cases is meant to show how complex failure conditions can be analyzed and used to determine inter-operability problems.
Anti-Virus Software Gone Wrong
Anti-virus software is becoming more and more prevalent on end-user computers today. Many major computer vendors (such as Dell) bundle anti-virus software and other personal security suites in the default configuration of newly-sold computer systems. As a result, it is becoming increasingly important that anti-virus software be well-designed, secure by default, and interoperable with third-party applications. Software that is installed and running by default constitutes a prime target for attack and, as such, it is especially important that said software be designed with security and interoperability in mind. In particular, this article provides examples of issues found in well-known anti-virus products. These issues range from not properly validating input from an untrusted source (especially within the context of a kernel driver) to failing to conform to API contracts when hooking or implementing an intermediary between applications and the underlying APIs upon which they rely. For popular software, or software that is installed by default, errors of this sort can become a serious problem to both system stability and security. Beyond that, it can impact the ability of independent software vendors to deploy functioning software on end-user systems.
Fingerprinting 802.11 Implementations via Statistical Analysis of the Duration Field
The research presented in this paper provides the reader with a set of algorithms and techniques that enable the user to remotely determine what chipset and device driver an 802.11 device is using. The technique outlined is entirely passive, and given the amount of features that are being considered for inclusion into the 802.11 standard, seems quite likely that it will increase in precision as the standard marches forward. The implications of this are far ranging. On one hand, the techniques can be used to implement innovative new features in Wireless Intrusion Detection Systems (WIDS). On the other, they can be used to target link layer device driver attacks with much higher precision.