Book Image

Learning Linux Binary Analysis

By : "elfmaster" O'Neill
5 (1)
Book Image

Learning Linux Binary Analysis

5 (1)
By: "elfmaster" O'Neill

Overview of this book

Learning Linux Binary Analysis is packed with knowledge and code that will teach you the inner workings of the ELF format, and the methods used by hackers and security analysts for virus analysis, binary patching, software protection and more. This book will start by taking you through UNIX/Linux object utilities, and will move on to teaching you all about the ELF specimen. You will learn about process tracing, and will explore the different types of Linux and UNIX viruses, and how you can make use of ELF Virus Technology to deal with them. The latter half of the book discusses the usage of Kprobe instrumentation for kernel hacking, code patching, and debugging. You will discover how to detect and disinfect kernel-mode rootkits, and move on to analyze static code. Finally, you will be walked through complex userspace memory infection analysis. This book will lead you into territory that is uncharted even by some experts; right into the world of the computer hacker.
Table of Contents (11 chapters)
10
Index

Direct sys_call_table modifications


Traditional kernel rootkits, such as adore and phalanx, worked by overwriting pointers in sys_call_table so that they would point to a replacement function, which would then call the original syscall as needed. This was accomplished by either an LKM or a program that modified the kernel through /dev/kmem or /dev/mem. On today's Linux systems, for security reasons, these writable windows into memory are disabled or are no longer capable of anything but read operations depending on how the kernel is configured. There have been other ways of trying to prevent this type of infection, such as marking sys_call_table as const so that it is stored in the .rodata section of the text segment. This can be bypassed by marking the corresponding PTE (short for Page Table Entry) as writeable, or by disabling the write-protect bit in the cr0 register. Therefore, this type of infection is a very reliable way to make a rootkit even today, but it is also very easily detected...