Process Injection: Proc Memory

Adversaries may inject malicious code into processes via the /proc filesystem in order to evade process-based defenses as well as possibly elevate privileges. Proc memory injection is a method of executing arbitrary code in the address space of a separate live process.

Proc memory injection involves enumerating the memory of a process via the /proc filesystem (/proc/[pid]) then crafting a return-oriented programming (ROP) payload with available gadgets/instructions. Each running process has its own directory, which includes memory mappings. Proc memory injection is commonly performed by overwriting the target processes’ stack using memory mappings provided by the /proc filesystem. This information can be used to enumerate offsets (including the stack) and gadgets (or instructions within the program that can be used to build a malicious payload) otherwise hidden by process memory protections such as address space layout randomization (ASLR). Once enumerated, the target processes’ memory map within /proc/[pid]/maps can be overwritten using dd.[1][2][3]

Other techniques such as LD_PRELOAD may be used to populate a target process with more available gadgets. Similar to Process Hollowing, proc memory injection may target child processes (such as a backgrounded copy of sleep).[2]

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 proc memory injection may also evade detection from security products since the execution is masked under a legitimate process.

ID: T1055.009
Sub-technique of:  T1055
Tactics: Defense Evasion, Privilege Escalation
Platforms: Linux
Data Sources: File monitoring, Process monitoring
Defense Bypassed: Anti-virus, Application control
Version: 1.0
Created: 14 January 2020
Last Modified: 20 June 2020

Mitigations

Mitigation Description
Behavior Prevention on Endpoint

Some endpoint security solutions can be configured to block some types of process injection based on common sequences of behavior that occur during the injection process.

Restrict File and Directory Permissions

Restrict the permissions on sensitive files such as /proc/[pid]/maps or /proc/[pid]/mem.

Detection

File system monitoring can determine if /proc files are being modified. Users should not have permission to modify these in most cases.

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