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Learning Linux Binary Analysis

You're reading from   Learning Linux Binary Analysis Learning Linux Binary Analysis

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Product type Paperback
Published in Feb 2016
Publisher Packt
ISBN-13 9781782167105
Length 282 pages
Edition 1st Edition
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Author (1):
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Ryan "elfmaster" O'Neill Ryan "elfmaster" O'Neill
Author Profile Icon Ryan "elfmaster" O'Neill
Ryan "elfmaster" O'Neill
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Table of Contents (11) Chapters Close

Preface 1. The Linux Environment and Its Tools FREE CHAPTER 2. The ELF Binary Format 3. Linux Process Tracing 4. ELF Virus Technology – Linux/Unix Viruses 5. Linux Binary Protection 6. ELF Binary Forensics in Linux 7. Process Memory Forensics 8. ECFS – Extended Core File Snapshot Technology 9. Linux /proc/kcore Analysis 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...

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