Query: Encoded PowerShell / command-line abuse matching Proc Memory
Matching passage: T1055.009 Proc Memory. Tactics: stealth, privilege escalation. Description: 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 (<code>/proc/[pid]</code>) 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 <code>/proc/[pid]/maps</code> can be overwritten using dd.(Citation: Uninformed Needle)(Citation: GDS Linux Injection)(Citation: DD Man) Other techniques such as [Dynamic Linker Hijacking](https://attack.mitre.org/techniques/T1574/006) may be used to populate a target process with more available gadgets. Similar to [Process Hollowing](https://attack.mitre.org/techniques/T1055/012), proc memory injection may target child processes (such as a backgrounded copy of sleep).(Citation: GDS Linux Injection) 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.
Near-miss passage: T1055.004 Asynchronous Procedure Call. Tactics: stealth, privilege escalation. Description: Adversaries may inject malicious code into processes via the asynchronous procedure call (APC) queue in order to evade process-based defenses as well as possibly elevate privileges. APC injection is a method of executing arbitrary code in the address space of a separate live process. APC injection is commonly performed by attaching malicious code to the APC Queue (Citation: Microsoft APC) of a process's thread. Queued APC functions are executed when the thread enters an alterable state.(Citation: Microsoft APC) A handle to an existing victim process is first created with native Windows API calls such as <code>OpenThread</code>. At this point <code>QueueUserAPC</code> can be used to invoke a function (such as <code>LoadLibrayA</code> pointing to a malicious DLL). A variation of APC injection, dubbed "Early Bird injection", involves creating a suspended process in which malicious code can be written and executed before the process' entry point (and potentially subsequent anti-malware hooks) via an APC. (Citation: CyberBit Early Bird Apr 2018) AtomBombing (Citation: ENSIL AtomBombing Oct 2016) is another variation that utilizes APCs to invoke malicious code previously written to the global atom table.(Citation: Microsoft Atom Table) 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 APC injection may also evade detection from security products since the execution is masked under a legitimate process.