Techniques

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]

Adversaries may abuse Regsvr32.exe to proxy execution of malicious code. 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. The Regsvr32.exe binary may also be signed by Microsoft. [1]

Malicious usage of Regsvr32.exe may avoid triggering security tools that may not monitor execution of, and modules loaded by, the regsvr32.exe process because of allowlists or false positives from Windows using regsvr32.exe for normal operations. Regsvr32.exe can also be used to specifically bypass application control 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" 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]

Once a payload is delivered, adversaries may reproduce copies of the same malware on the victim system to remove evidence of their presence and/or avoid defenses. Copying malware payloads to new locations may also be combined with File Deletion to cleanup older artifacts.

Relocating malware may be a part of many actions intended to evade defenses. For example, adversaries may copy and rename payloads to better blend into the local environment (i.e., Match Legitimate Resource Name or Location).[1] Payloads may also be repositioned to target File/Path Exclusions as well as specific locations associated with establishing Persistence.[2]

Relocating malicious payloads may also hinder defensive analysis, especially to separate these payloads from earlier events (such as User Execution and Phishing) that may have generated alerts or otherwise drawn attention from defenders. Moving payloads into target directories does not alter the Creation timestamp, thereby evading detection logic reliant on modifications to this artifact (i.e., Timestomp).

An adversary may use legitimate remote access hardware to establish an interactive command and control channel to target systems within networks. These services, including IP-based keyboard, video, or mouse (KVM) devices such as TinyPilot and PiKVM, are commonly used as legitimate tools and may be allowed by peripheral device policies within a target environment.

Remote access hardware may be physically installed and used post-compromise as an alternate communications channel for redundant access or as a way to establish an interactive remote session with the target system. Using hardware-based remote access tools may allow threat actors to bypass software security solutions and gain more control over the compromised device(s).[1][2]

Adversaries may use legitimate remote access software, such as `VNC`, `TeamViewer`, `AirDroid`, `AirMirror`, etc., to establish an interactive command and control channel to target mobile devices.

Remote access applications may be installed and used post-compromise as an alternate communication channel for redundant access or as a way to establish an interactive remote session with the target device. They may also be used as a component of malware to establish a reverse connection to an adversary-controlled system or service. Installation of remote access tools may also include persistence.

An adversary may use legitimate remote access tools to establish an interactive command and control channel within a network. Remote access tools create a session between two trusted hosts through a graphical interface, a command line interaction, a protocol tunnel via development or management software, or hardware-level access such as KVM (Keyboard, Video, Mouse) over IP solutions. Desktop support software (usually graphical interface) and remote management software (typically command line interface) allow a user to control a computer remotely as if they are a local user inheriting the user or software permissions. This software is commonly used for troubleshooting, software installation, and system management.[1][2][3] Adversaries may similarly abuse response features included in EDR and other defensive tools that enable remote access.

Remote access tools may be installed and used post-compromise as an alternate communications channel for redundant access or to establish an interactive remote desktop session with the target system. It may also be used as a malware component to establish a reverse connection or back-connect to a service or adversary-controlled system.

Installation of many remote access tools may also include persistence (e.g., the software's installation routine creates a Windows Service). Remote access modules/features may also exist as part of otherwise existing software (e.g., Google Chrome’s Remote Desktop).[4][5]

Adversaries may stage data collected from multiple systems in a central location or directory on one system prior to Exfiltration. Data may be kept in separate files or combined into one file through techniques such as Archive Collected Data. Interactive command shells may be used, and common functionality within cmd and bash may be used to copy data into a staging location.

In cloud environments, adversaries may stage data within a particular instance or virtual machine before exfiltration. An adversary may Create Cloud Instance and stage data in that instance.[1]

By staging data on one system prior to Exfiltration, adversaries can minimize the number of connections made to their C2 server and better evade detection.

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] There are other implementations and third-party tools that provide graphical access Remote Services similar to RDS.

Adversaries may connect to a remote system over RDP/RDS to expand access if the service is enabled and allows access to accounts with known credentials. Adversaries will likely use Credential Access techniques to acquire credentials to use with RDP. Adversaries may also use RDP in conjunction with the Accessibility Features technique for Persistence. [2]

Adversaries may also 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 and prompted with a question. 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. [3] This can be done remotely or locally and with active or disconnected sessions. [4] 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 RedSnarf. [5]

Adversaries may use Valid Accounts to log into a computer using the Remote Desktop Protocol (RDP). The adversary may then perform actions as the logged-on user.

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 connect to a remote system over RDP/RDS to expand access if the service is enabled and allows access to accounts with known credentials. Adversaries will likely use Credential Access techniques to acquire credentials to use with RDP. Adversaries may also use RDP in conjunction with the Accessibility Features or Terminal Services DLL for Persistence.[2]

An adversary may use legitimate desktop support software to establish an interactive command and control channel to target systems within networks. Desktop support software provides a graphical interface for remotely controlling another computer, transmitting the display output, keyboard input, and mouse control between devices using various protocols. Desktop support software, such as `VNC`, `Team Viewer`, `AnyDesk`, `ScreenConnect`, `LogMein`, `AmmyyAdmin`, and other remote monitoring and management (RMM) tools, are commonly used as legitimate technical support software and may be allowed by application control within a target environment.[1][2][3] Remote access modules/features may also exist as part of otherwise existing software such as Zoom or Google Chrome’s Remote Desktop.[4][5]

An adversary may use access to cloud services (e.g. Google's Android Device Manager or Apple iCloud's Find my iPhone) or to an enterprise mobility management (EMM)/mobile device management (MDM) server console to track the location of mobile devices managed by the service.[1]

Adversaries may target an Exchange server, Office 365, or Google Workspace to collect sensitive information. Adversaries may leverage a user's credentials and interact directly with the Exchange server to acquire information from within a network. Adversaries may also access externally facing Exchange services, Office 365, or Google Workspace to access email using credentials or access tokens. Tools such as MailSniper can be used to automate searches for specific keywords.[1]