VDSO Hijacking

Adversaries may inject malicious code into processes via VDSO hijacking in order to evade process-based defenses as well as possibly elevate privileges. Virtual dynamic shared object (vdso) hijacking is a method of executing arbitrary code in the address space of a separate live process. 

VDSO hijacking involves redirecting calls to dynamically linked shared libraries. Memory protections may prevent writing executable code to a process via [Ptrace System Calls](https://attack.mitre.org/techniques/T1055/008). However, an adversary may hijack the syscall interface code stubs mapped into a process from the vdso shared object to execute syscalls to open and map a malicious shared object. This code can then be invoked by redirecting the execution flow of the process via patched memory address references stored in a process' global offset table (which store absolute addresses of mapped library functions).(Citation: ELF Injection May 2009)(Citation: Backtrace VDSO)(Citation: VDSO Aug 2005)(Citation: Syscall 2014)

Running code in the context of another process may allow access to the process's memory, system/network resources, and possibly elevated privileges. Execution via VDSO hijacking may also evade detection from security products since the execution is masked under a legitimate process.  

Platforms: Linux
Tactics:
phase_name: defense-evasion
phase_name: privilege-escalation

Detection:
Monitor for malicious usage of system calls, such as ptrace and mmap, that can be used to attach to, manipulate memory, then redirect a processes' execution path. Monitoring for Linux specific calls such as the ptrace system call should not generate large amounts of data due to their specialized nature, and can be a very effective method to detect some of the common process injection methods.(Citation: ArtOfMemoryForensics)(Citation: GNU Acct)(Citation: RHEL auditd)(Citation: Chokepoint preload rootkits) 

Analyze process behavior to determine if a process is performing actions it usually does not, such as opening network connections, reading files, or other suspicious actions that could relate to post-compromise behavior. 

References:
source_name: mitre-attack
description: backtrace. (2016, April 22). ELF SHARED LIBRARY INJECTION FORENSICS. Retrieved June 15, 2020.
source_name: Backtrace VDSO
description: Drysdale, D. (2014, July 16). Anatomy of a system call, part 2. Retrieved June 16, 2020.
source_name: Syscall 2014
description: GNU. (2010, February 5). The GNU Accounting Utilities. Retrieved December 20, 2017.
source_name: GNU Acct
description: Jahoda, M. et al.. (2017, March 14). redhat Security Guide - Chapter 7 - System Auditing. Retrieved December 20, 2017.
source_name: RHEL auditd
description: Ligh, M.H. et al.. (2014, July). The Art of Memory Forensics: Detecting Malware and Threats in Windows, Linux, and Mac Memory. Retrieved December 20, 2017.
source_name: ArtOfMemoryForensics
description: O'Neill, R. (2009, May). Modern Day ELF Runtime infection via GOT poisoning. Retrieved March 15, 2020.
source_name: ELF Injection May 2009
description: Petersson, J. (2005, August 14). What is linux-gate.so.1?. Retrieved June 16, 2020.
source_name: VDSO Aug 2005
description: stderr. (2014, February 14). Detecting Userland Preload Rootkits. Retrieved December 20, 2017.
source_name: Chokepoint preload rootkits