|T1055.001||Dynamic-link Library Injection|
|T1055.002||Portable Executable Injection|
|T1055.003||Thread Execution Hijacking|
|T1055.004||Asynchronous Procedure Call|
|T1055.005||Thread Local Storage|
|T1055.008||Ptrace System Calls|
|T1055.011||Extra Window Memory Injection|
Adversaries may inject dynamic-link libraries (DLLs) into processes in order to evade process-based defenses as well as possibly elevate privileges. DLL injection is a method of executing arbitrary code in the address space of a separate live process.
DLL injection is commonly performed by writing the path to a DLL in the virtual address space of the target process before loading the DLL by invoking a new thread. The write can be performed with native Windows API calls such as
WriteProcessMemory, then invoked with
CreateRemoteThread (which calls the
LoadLibrary API responsible for loading the DLL). 
Variations of this method such as reflective DLL injection (writing a self-mapping DLL into a process) and memory module (map DLL when writing into process) overcome the address relocation issue as well as the additional APIs to invoke execution (since these methods load and execute the files in memory by manually preforming the function of
Another variation of this method, often referred to as Module Stomping/Overloading or DLL Hollowing, may be leveraged to conceal injected code within a process. This method involves loading a legitimate DLL into a remote process then manually overwriting the module's
AddressOfEntryPoint before starting a new thread in the target process. This variation allows attackers to hide malicious injected code by potentially backing its execution with a legitimate DLL file on disk.
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 DLL injection may also evade detection from security products since the execution is masked under a legitimate process.
ComRAT has injected its orchestrator DLL into explorer.exe. ComRAT has also injected its communications module into the victim's default browser to make C2 connections appear less suspicious as all network connections will be initiated by the browser process.
Duqu will inject itself into different processes to evade detection. The selection of the target process is influenced by the security software that is installed on the system (Duqu will inject into different processes depending on which security suite is installed on the infected host).
If running in a Windows environment, Kazuar saves a DLL to disk that is injected into the explorer.exe process to execute the payload. Kazuar can also be configured to inject and execute within specific processes.
An executable dropped onto victims by Putter Panda aims to inject the specified DLL into a process that would normally be accessing the network, including Outlook Express (msinm.exe), Outlook (outlook.exe), Internet Explorer (iexplore.exe), and Firefox (firefox.exe).
After decrypting itself in memory, RARSTONE downloads a DLL file from its C2 server and loads it in the memory space of a hidden Internet Explorer process. This "downloaded" file is actually not dropped onto the system.
|M1040||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.
|ID||Data Source||Data Component||Detects|
Monitor DLL/PE file events, specifically creation of these binary files as well as the loading of DLLs into processes. Look for DLLs that are not recognized or not normally loaded into a process. Sysmon Event ID 7 (Image loaded) can be used to monitor the loading of DLLs into processes. This is a particularly noisy event and can generate a large volume of data, so we recommend baselining and filtering out any known benign processes and module loads to help reduce the number of events that are produced.
|DS0009||Process||OS API Execution||
Monitoring Windows API calls indicative of the various types of code injection may generate a significant amount of data and may not be directly useful for defense unless collected under specific circumstances for known bad sequences of calls, since benign use of API functions may be common and difficult to distinguish from malicious behavior. Windows API calls such as
Search for remote thread creations that start at LoadLibraryA or LoadLibraryW. Depending on the tool, it may provide additional information about the DLL string that is an argument to the function. If there is any security software that legitimately injects DLLs, it must be carefully whitelisted.
Microsoft Windows allows for processes to remotely create threads within other processes of the same privilege level. This functionality is provided via the Windows API CreateRemoteThread. Both Windows and third-party software use this ability for legitimate purposes. For example, the Windows process csrss.exe creates threads in programs to send signals to registered callback routines. Both adversaries and host-based security software use this functionality to inject DLLs, but for very different purposes. An adversary is likely to inject into a program to evade defenses or bypass User Account Control, but a security program might do this to gain increased monitoring of API calls. One of the most common methods of DLL Injection is through the Windows API LoadLibrary.
This behavior can be detected by looking for thread creations across processes, and resolving the entry point to determine the function name. If the function is LoadLibraryA or LoadLibraryW, then the intent of the remote thread is clearly to inject a DLL. When this is the case, the source process must be examined so that it can be ignored when it is both expected and a trusted process.
Analytic 1 - DLL Injection via Load Library
Monitor for process being viewed that may inject dynamic-link libraries (DLLs) into processes in order to evade process-based defenses as well as possibly elevate privileges.
Monitor for process memory inconsistencies compared to DLL files on disk by checking memory ranges against a known copy of the legitimate module.
Monitor for changes made to processes that may inject dynamic-link libraries (DLLs) into processes in order to evade process-based defenses as well as possibly elevate privileges. Injecting a malicious DLL into a process is a common adversary TTP. Although the ways of doing this are numerous, mavinject.exe is a commonly used tool for doing so because it roles up many of the necessary steps into one, and is available within Windows. Attackers may rename the executable, so we also use the common argument "INJECTRUNNING" as a related signature here. Whitelisting certain applications may be necessary to reduce noise for this analytic.
Analytic 1 - DLL Injection with Mavinject