Ptrace System Calls

Adversaries may inject malicious code into processes via ptrace (process trace) system calls in order to evade process-based defenses as well as possibly elevate privileges. Ptrace system call injection is a method of executing arbitrary code in the address space of a separate live process. 

Ptrace system call injection involves attaching to and modifying a running process. The ptrace system call enables a debugging process to observe and control another process (and each individual thread), including changing memory and register values.(Citation: PTRACE man) Ptrace system call injection is commonly performed by writing arbitrary code into a running process (ex: <code>malloc</code>) then invoking that memory with <code>PTRACE_SETREGS</code> to set the register containing the next instruction to execute. Ptrace system call injection can also be done with <code>PTRACE_POKETEXT</code>/<code>PTRACE_POKEDATA</code>, which copy data to a specific address in the target processes’ memory (ex: the current address of the next instruction). (Citation: PTRACE man)(Citation: Medium Ptrace JUL 2018) 

Ptrace system call injection may not be possible targeting processes that are non-child processes and/or have higher-privileges.(Citation: BH Linux Inject) 

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 ptrace system call injection 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:
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: Kerrisk, M. (2020, February 9). PTRACE(2) - Linux Programmer's Manual. Retrieved February 21, 2020.
source_name: PTRACE man
description: Jain, S. (2018, July 25). Code injection in running process using ptrace. Retrieved February 21, 2020.
source_name: Medium Ptrace JUL 2018
description: Colgan, T. (2015, August 15). Linux-Inject. Retrieved February 21, 2020.
source_name: BH Linux Inject
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: 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: stderr. (2014, February 14). Detecting Userland Preload Rootkits. Retrieved December 20, 2017.
source_name: Chokepoint preload rootkits