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. Ptrace system call injection is commonly performed by writing arbitrary code into a running process (e.g., by using
malloc) then invoking that memory with
PTRACE_SETREGS to set the register containing the next instruction to execute. Ptrace system call injection can also be done with
PTRACE_POKEDATA, which copy data to a specific address in the target process's memory (e.g., the current address of the next instruction).
Ptrace system call injection may not be possible when targeting processes with high-privileges, and on some systems those that are non-child processes.
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.
Triada injects code into the Zygote process to effectively include itself in all forked processes. Additionally, code is injected into the Android Play Store App, web browser applications, and the system UI application.
This type of attack technique cannot be easily mitigated with preventive controls since it is based on the abuse of system features.
Application vetting services could look for misuse of dynamic libraries.