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Architecture 2001: x86-64 OS Internals


About This Course

This is it! This is the class that *actually* teaches you how ring 0 vs. ring 3 privilege separation works at a deep deep level on Intel hardware!!! But so much more too! This class gives you an incredibly strong foundation for Windows, Linux, *BSD, or macOS OS Internals classes. Because if covers the hardware-specific requirements that every OS (or VMM or BIOS) must deal with if they want to run on Intel hardware.

After this class you will feel exploring wherever you want in the Intel manuals, because this class covers some of the most difficult to understand underlying technologies that OSes depend on.

Topics include, but are not limited to:
•Physical and virtual memory and how a limited amount of physical memory is represented as much more virtual memory through a multilevel paging system. We will also talk about memory segmentation.
•The hardware basis for kernel versus userspace separation and how software transitions between the two. This portion answers the question of why does x86 have 4 “rings”, with ring 0 being the most privileged, and ring 3 being the least.
•Hardware and software interrupts, and how they are the basis for debugging.
•Input/Output instructions and how these allow the CPU to talk to peripherals.

Example applications include showing how hardware and memory mechanisms are used for software exploits, anti-debug techniques, and rootkit hiding.


You must be comfortable with C programming.

You must have taken OST2 Architecture 1001, or have equivalent knowledge of assembly.

Frequently Asked Questions

What learning paths is this class used in?

Exploits, Reverse Engineering, Malware Analysis, and System Security

Does the instructor teach this class in person?

Yes, but only occasionally. Xeno's preferred in-person delivery method is a hybrid structure where we get everyone in the same room, and students proceed through the class at their own pace by watching videos. Xeno is then available in person and chat to answer questions immediately when they occur. This is called an "OST2 All-you-can-learn Buffet" (OST2-B) class. The next such class will be held at CanSecWest May 14-17th 2022. He only does "live-lecture" classes for companies that have sponsored OST2, if they insist that they want this anachronistic and arguably suboptimal delivery method.

To be or not to be?

That is the question...

Course Staff

Xeno's Twitter Pic!

Xeno Kovah

Xeno founded OpenSecurityTraining in 2011 to share his and others' trainings more widely. He relaunched OST2 in 2021.

Xeno's from Minnesota and has a BS in CS from UMN. He received a MS in computer security from Carnegie Mellon through the National Science Foundation "CyberCorps Scholarship for Service". But the US government didn't really yet know what to do with "cyber" people in 2007; so he ended up going to work for a Federally Funded Research and Development Center - MITRE. Xeno worked exclusively on internal-funded research projects, first as a participant and later as a leader on Windows kernel malware detection and trusted computing projects. Towards the end, other cool researchers inspired him to dig into BIOS and firmware level threats.

Xeno left MITRE to start an independent consultancy, LegbaCore, with Corey Kallenberg in 2015. Less than a year later, under mysterious circumstances that he's legally prevented from stating, he started working for Apple. While at Apple he helped get SecureBoot on Macs with the addition of the T2 chip. He also led the SecureBoot design and implementation project for the ARM-based M1 Macs. But between those big, visible, multi-year, projects, he was silently improving the security of a bunch of the 3rd party peripheral processors' hardware and firmware. He liked working at Apple because he had a bully pulpit where he could force 3rd parties to do the right thing or lose their business. But he likes OST better, so he left in 2020 to work on this full time.

Xeno has a touch of the illness known as being a "collector" (it's not quite to the level of being a "hoarder", so he can't get on TV for it or anything...) Consequently he has presented at IEEE S&P, ACM CCS, BlackHat USA/EUR, Defcon, CanSecWest, PacSec, Hack in the Box KUL/AMS/GSEC, Microsoft BlueHat, Shmoocon,, NoSuchCon, SummerCon, RSA, ToorCon, DeepSec, VirusBulletin, MIRCon, AusCERT, Trusted Infrastructure Workshop, NIST NICE Workshop, and the DOD Information Assurance Symposium. And yet he still says "MORE!"