Technical Explorations

Beyond Process and Object Callbacks: An Unconventional Method

Overview In this article, I wanted to introduce a fun approach to performing functions similar to those enabled by Windows Object Callbacks but through an alternative means. It’s well known that anti-malware, anti-cheat, and generic monitoring tools on Windows systems often use these callbacks. However, their usability is limited to parties with signed modules, and […]

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Fun with another PG-compliant Hook

Overview In this article, we’ll be covering a fun alternative to the treasured InfinityHook from Nick Peterson. This alternative method was discovered by Aidan Khoury¬†following the release and subsequent patch of the EtwpGetCycleCount target by Microsoft without any acknowledgements to the original authors. This method has been tested from early Windows 10 to latest Windows […]

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Evading ACPI checks in commercial virtualization platforms

Overview Dozens of virtual machine checks are scattered throughout various open-source projects. You’ll see a handful of the same checks in various applications, from commercial to fully fleshed-out malware. The checks typically involve looking for drivers, devices, processes, registry entries, custom vendor information, timing attacks, etc. Most of these methods are easily mitigated by tweaking […]

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MMU Virtualization via Intel EPT: Implementation – Part 1

Overview This article will cover the various requirements and features available for MMU virtualization via Intel Extended Page Tables. It’s going to be a relatively long article as I want to cover all of or most of the details concerning initialization and capability checking, MTRR setup, page splitting, and so on. We’ll start with checking […]

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MMU Virtualization via Intel EPT: Technical Details

Overview This article marks the first of 5 articles covering the virtualization of the memory management unit (MMU) using Intel EPT. This technology is used as additional support for the virtualization of physical memory and allows hypervisors to monitor memory activity. This article will address the motivation for extended page tables, the many performance concerns […]

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MMU Virtualization via Intel EPT – Index

Overview After receiving an abundance of requests to complete the EPT series I’ve switched gears to write this 5 part series over MMU Virtualization using Intel EPT. This series is written to be able to be used in your own hypervisor project or in conjunction with the CPU virtualization series published a few months prior. […]

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Patchguard: Detection of Hypervisor Based Introspection [P2]

No Errata For U! If you haven’t already, read Part 1 which outlines three neat tricks used by Patchguard. KiErrata420Present The LSTAR MSR can be intercepted using a hypervisor to trap on reads and writes. It is the most common and efficient way to hook syscalls in most modern x86 operating systems. However contrary to […]

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Patchguard: Detection of Hypervisor Based Introspection [P1]

Errata Or Nah? Over the last 2-3 years, Microsoft has inserted various methods of virtualization introspection detection (big brain words) into the workings of patchguard. It shouldn’t come as surprise that this has happened, as subverting kernel patch protection is a breeze when the attacker code is running at a higher privilege level. While Windows […]

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Applied Reverse Engineering: Accelerated Assembly [P2]

Overview After reading feedback from the first part to the Accelerated Assembly guide, I’ve decided to take on a custom target, and call back to high-level languages when we encounter obscure or new pieces in the assembly. I realize that the level of detail in my last article may have been cumbersome to some readers, […]

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Applied Reverse Engineering: Accelerated Assembly [P1]

Overview In this article you’ll be guided through a course on the x86 Instruction Set. This article serves at as a quick fix to the problem of not knowing where to start when learning Assembly. We’ll be covering instruction format briefly, and then jump right in to the instructions. This is like learning another language, […]

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