Techniques

Adversaries may execute their own malicious payloads by hijacking environment variables used to load libraries. The PATH environment variable contains a list of directories (User and System) that the OS searches sequentially through in search of the binary that was called from a script or the command line.

Adversaries can place a malicious program in an earlier entry in the list of directories stored in the PATH environment variable, resulting in the operating system executing the malicious binary rather than the legitimate binary when it searches sequentially through that PATH listing.

For example, on Windows if an adversary places a malicious program named "net.exe" in `C:\example path`, which by default precedes `C:\Windows\system32\net.exe` in the PATH environment variable, when "net" is executed from the command-line the `C:\example path` will be called instead of the system's legitimate executable at `C:\Windows\system32\net.exe`. Some methods of executing a program rely on the PATH environment variable to determine the locations that are searched when the path for the program is not given, such as executing programs from a Command and Scripting Interpreter.[1]

Adversaries may also directly modify the $PATH variable specifying the directories to be searched. An adversary can modify the `$PATH` variable to point to a directory they have write access. When a program using the $PATH variable is called, the OS searches the specified directory and executes the malicious binary. On macOS, this can also be performed through modifying the $HOME variable. These variables can be modified using the command-line, launchctl, Unix Shell Configuration Modification, or modifying the `/etc/paths.d` folder contents.[2][3][4]

Adversaries may execute their own malicious payloads by hijacking the search order used to load other programs. Because some programs do not call other programs using the full path, adversaries may place their own file in the directory where the calling program is located, causing the operating system to launch their malicious software at the request of the calling program.

Search order hijacking occurs when an adversary abuses the order in which Windows searches for programs that are not given a path. Unlike DLL search order hijacking, the search order differs depending on the method that is used to execute the program. [1] [2] [3] However, it is common for Windows to search in the directory of the initiating program before searching through the Windows system directory. An adversary who finds a program vulnerable to search order hijacking (i.e., a program that does not specify the path to an executable) may take advantage of this vulnerability by creating a program named after the improperly specified program and placing it within the initiating program's directory.

For example, "example.exe" runs "cmd.exe" with the command-line argument net user. An adversary may place a program called "net.exe" within the same directory as example.exe, "net.exe" will be run instead of the Windows system utility net. In addition, if an adversary places a program called "net.com" in the same directory as "net.exe", then cmd.exe /C net user will execute "net.com" instead of "net.exe" due to the order of executable extensions defined under PATHEXT. [4]

Search order hijacking is also a common practice for hijacking DLL loads and is covered in DLL.

Adversaries may execute their own malicious payloads by hijacking vulnerable file path references. Adversaries can take advantage of paths that lack surrounding quotations by placing an executable in a higher level directory within the path, so that Windows will choose the adversary's executable to launch.

Service paths [1] and shortcut paths may also be vulnerable to path interception if the path has one or more spaces and is not surrounded by quotation marks (e.g., C:\unsafe path with space\program.exe vs. "C:\safe path with space\program.exe"). [2] (stored in Windows Registry keys) An adversary can place an executable in a higher level directory of the path, and Windows will resolve that executable instead of the intended executable. For example, if the path in a shortcut is C:\program files\myapp.exe, an adversary may create a program at C:\program.exe that will be run instead of the intended program. [3] [4]

This technique can be used for persistence if executables are called on a regular basis, as well as privilege escalation if intercepted executables are started by a higher privileged process.

Adversaries may attempt to gather information about attached peripheral devices and components connected to a computer system.[1][2] Peripheral devices could include auxiliary resources that support a variety of functionalities such as keyboards, printers, cameras, smart card readers, or removable storage. The information may be used to enhance their awareness of the system and network environment or may be used for further actions.

Adversaries may attempt to discover group and permission settings. This information can help adversaries determine which user accounts and groups are available, the membership of users in particular groups, and which users and groups have elevated permissions.

Adversaries may attempt to discover group permission settings in many different ways. This data may provide the adversary with information about the compromised environment that can be used in follow-on activity and targeting.[1]

Adversaries may send phishing messages to gain access to victim systems. All forms of phishing are electronically delivered social engineering. Phishing can be targeted, known as spearphishing. In spearphishing, a specific individual, company, or industry will be targeted by the adversary. More generally, adversaries can conduct non-targeted phishing, such as in mass malware spam campaigns.

Adversaries may send victims emails containing malicious attachments or links, typically to execute malicious code on victim systems. Phishing may also be conducted via third-party services, like social media platforms. Phishing may also involve social engineering techniques, such as posing as a trusted source, as well as evasive techniques such as removing or manipulating emails or metadata/headers from compromised accounts being abused to send messages (e.g., Email Hiding Rules).[1][2] Another way to accomplish this is by Email Spoofing[3] the identity of the sender, which can be used to fool both the human recipient as well as automated security tools,[4] or by including the intended target as a party to an existing email thread that includes malicious files or links (i.e., "thread hijacking").[5]

Victims may also receive phishing messages that instruct them to call a phone number where they are directed to visit a malicious URL, download malware,[6][7] or install adversary-accessible remote management tools onto their computer (i.e., User Execution).[8]

Adversaries may send malicious content to users in order to gain access to their mobile devices. All forms of phishing are electronically delivered social engineering. Adversaries can conduct both non-targeted phishing, such as in mass malware spam campaigns, as well as more targeted phishing tailored for a specific individual, company, or industry, known as “spearphishing.” Phishing often involves social engineering techniques, such as posing as a trusted source, as well as evasion techniques, such as removing or manipulating emails or metadata/headers from compromised accounts being abused to send messages.

Mobile phishing may take various forms. For example, adversaries may send emails containing malicious attachments or links, typically to deliver and then execute malicious code on victim devices. Phishing may also be conducted via third-party services, like social media platforms. Adversaries may also impersonate executives of organizations to persuade victims into performing some action on their behalf. For example, adversaries will often use social engineering techniques in text messages to trick the victims into acting quickly, which leads to adversaries obtaining credentials and other information.

Mobile devices are a particularly attractive target for adversaries executing phishing campaigns. Due to their smaller form factor than traditional desktop endpoints, users may not be able to notice minor differences between genuine and phishing websites. Further, mobile devices have additional sensors and radios that allow adversaries to execute phishing attempts over several different vectors, such as:

- SMS messages: Adversaries may send SMS messages (known as “smishing”) from compromised devices to potential targets to convince the target to, for example, install malware, navigate to a specific website, or enable certain insecure configurations on their device. - Quick Response (QR) Codes: Adversaries may use QR codes (known as “quishing”) to redirect users to a phishing website. For example, an adversary could replace a legitimate public QR Code with one that leads to a different destination, such as a phishing website. A malicious QR code could also be delivered via other means, such as SMS or email. In the latter case, an adversary could utilize a malicious QR code in an email to pivot from the user’s desktop computer to their mobile device. - Phone Calls: Adversaries may call victims (known as "vishing") to persuade them to perform an action, such as providing login credentials or navigating to malicious websites. Common vishing targets include employees, especially executives of organizations, and help desks. This may also be used as a technique to perform the initial access on a mobile device, but then pivot to a desktop computer by having the victims perform actions on a desktop computer. With the rise of artificial intelligence (AI), adversaries may also use AI to clone a person’s voice, resulting in deepfake vishing. The cloned voice provides familiarity to the victims, increasing the likelihood of successful malicious actions performed by the victims. Additionally, adversaries may leave voicemails, which may use a real person’s voice or an AI-generated voice; these scams would urgently ask victims into calling back to perform an action, e.g. sending money or providing sensitive information and credentials.

Adversaries may send phishing messages to elicit sensitive information that can be used during targeting. Phishing for information is an attempt to trick targets into divulging information, frequently credentials or other actionable information. Phishing for information is different from Phishing in that the objective is gathering data from the victim rather than executing malicious code.

All forms of phishing are electronically delivered social engineering. Phishing can be targeted, known as spearphishing. In spearphishing, a specific individual, company, or industry will be targeted by the adversary. More generally, adversaries can conduct non-targeted phishing, such as in mass credential harvesting campaigns.

Adversaries may also try to obtain information directly through the exchange of emails, instant messages, or other electronic conversation means.[1][2][3][4][5] Victims may also receive phishing messages that direct them to call a phone number where the adversary attempts to collect confidential information.[6]

Phishing for information frequently involves social engineering techniques, such as posing as a source with a reason to collect information (ex: Establish Accounts or Compromise Accounts) and/or sending multiple, seemingly urgent messages. Another way to accomplish this is by Email Spoofing[7] the identity of the sender, which can be used to fool both the human recipient as well as automated security tools.[8]

Phishing for information may also involve evasive techniques, such as removing or manipulating emails or metadata/headers from compromised accounts being abused to send messages (e.g., Email Hiding Rules).[9][10]

Adversaries may modify property list files (plist files) to enable other malicious activity, while also potentially evading and bypassing system defenses. macOS applications use plist files, such as the info.plist file, to store properties and configuration settings that inform the operating system how to handle the application at runtime. Plist files are structured metadata in key-value pairs formatted in XML based on Apple's Core Foundation DTD. Plist files can be saved in text or binary format.[1]

Adversaries can modify key-value pairs in plist files to influence system behaviors, such as hiding the execution of an application (i.e. Hidden Window) or running additional commands for persistence (ex: Launch Agent/Launch Daemon or Re-opened Applications).

For example, adversaries can add a malicious application path to the `~/Library/Preferences/com.apple.dock.plist` file, which controls apps that appear in the Dock. Adversaries can also modify the LSUIElement key in an application’s info.plist file to run the app in the background. Adversaries can also insert key-value pairs to insert environment variables, such as LSEnvironment, to enable persistence via Dynamic Linker Hijacking.[2][3]

Adversaries may modify pluggable authentication modules (PAM) to access user credentials or enable otherwise unwarranted access to accounts. PAM is a modular system of configuration files, libraries, and executable files which guide authentication for many services. The most common authentication module is pam_unix.so, which retrieves, sets, and verifies account authentication information in /etc/passwd and /etc/shadow.[1][2][3]

Adversaries may modify components of the PAM system to create backdoors. PAM components, such as pam_unix.so, can be patched to accept arbitrary adversary supplied values as legitimate credentials.[4]

Malicious modifications to the PAM system may also be abused to steal credentials. Adversaries may infect PAM resources with code to harvest user credentials, since the values exchanged with PAM components may be plain-text since PAM does not store passwords.[5][1]

Adversaries may collect point and tag values to gain a more comprehensive understanding of the process environment. Points may be values such as inputs, memory locations, outputs or other process specific variables. [1] Tags are the identifiers given to points for operator convenience.

Collecting such tags provides valuable context to environmental points and enables an adversary to map inputs, outputs, and other values to their control processes. Understanding the points being collected may inform an adversary on which processes and values to keep track of over the course of an operation.

Adversaries may utilize polymorphic code (also known as metamorphic or mutating code) to evade detection. Polymorphic code is a type of software capable of changing its runtime footprint during code execution.[1] With each execution of the software, the code is mutated into a different version of itself that achieves the same purpose or objective as the original. This functionality enables the malware to evade traditional signature-based defenses, such as antivirus and antimalware tools.[2] Other obfuscation techniques can be used in conjunction with polymorphic code to accomplish the intended effects, including using mutation engines to conduct actions such as Software Packing, Command Obfuscation, or Encrypted/Encoded File.[3][4]

Adversaries may use port knocking to hide open ports used for persistence or command and control. To enable a port, an adversary sends a series of attempted connections to a predefined sequence of closed ports. After the sequence is completed, opening a port is often accomplished by the host based firewall, but could also be implemented by custom software.

This technique has been observed both for the dynamic opening of a listening port as well as the initiating of a connection to a listening server on a different system.

The observation of the signal packets to trigger the communication can be conducted through different methods. One means, originally implemented by Cd00r [1], is to use the libpcap libraries to sniff for the packets in question. Another method leverages raw sockets, which enables the malware to use ports that are already open for use by other programs.

Adversaries may use port monitors to run an adversary supplied DLL during system boot for persistence or privilege escalation. A port monitor can be set through the AddMonitor API call to set a DLL to be loaded at startup.[1] This DLL can be located in C:\Windows\System32 and will be loaded and run by the print spooler service, `spoolsv.exe`, under SYSTEM level permissions on boot.[2]

Alternatively, an arbitrary DLL can be loaded if permissions allow writing a fully-qualified pathname for that DLL to the `Driver` value of an existing or new arbitrarily named subkey of HKLM\SYSTEM\CurrentControlSet\Control\Print\Monitors. The Registry key contains entries for the following:

* Local Port * Standard TCP/IP Port * USB Monitor * WSD Port

Adversaries may perform a port scan on a system, device, or network to identify live hosts, enumerate open ports and running services, identify operating systems, and map out the network.[1] The results of a port scan may inform adversary Discovery, Lateral Movement, and vulnerability exploitation decisions (Exploitation for Evasion, Exploitation for Privilege Escalation, Exploitation of Remote Services).

Some common tools for executing a port scan include `nmap`, `netcat`, and the Advanced Port Scanner.

Adversaries may inject portable executables (PE) into processes in order to evade process-based defenses as well as possibly elevate privileges. PE injection is a method of executing arbitrary code in the address space of a separate live process.

PE injection is commonly performed by copying code (perhaps without a file on disk) into the virtual address space of the target process before invoking it via a new thread. The write can be performed with native Windows API calls such as VirtualAllocEx and WriteProcessMemory, then invoked with CreateRemoteThread or additional code (ex: shellcode). The displacement of the injected code does introduce the additional requirement for functionality to remap memory references. [1]

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

Adversaries may impair a system's ability to hibernate, reboot, or shut down in order to extend access to infected machines. When a computer enters a dormant state, some or all software and hardware may cease to operate which can disrupt malicious activity.[1]

Adversaries may abuse system utilities and configuration settings to maintain access by preventing machines from entering a state, such as standby, that can terminate malicious activity.[2][3]

For example, `powercfg` controls all configurable power system settings on a Windows system and can be abused to prevent an infected host from locking or shutting down.[4] Adversaries may also extend system lock screen timeout settings.[5] Other relevant settings, such as disk and hibernate timeout, can be similarly abused to keep the infected machine running even if no user is active.[6]

Aware that some malware cannot survive system reboots, adversaries may entirely delete files used to invoke system shut down or reboot.[7]

Adversaries may abuse PowerShell commands and scripts for execution. PowerShell is a powerful interactive command-line interface and scripting environment included in the Windows operating system.[1] Adversaries can use PowerShell to perform a number of actions, including discovery of information and execution of code. Examples include the Start-Process cmdlet which can be used to run an executable and the Invoke-Command cmdlet which runs a command locally or on a remote computer (though administrator permissions are required to use PowerShell to connect to remote systems).

PowerShell may also be used to download and run executables from the Internet, which can be executed from disk or in memory without touching disk.

A number of PowerShell-based offensive testing tools are available, including Empire, PowerSploit, PoshC2, and PSAttack.[2]

PowerShell commands/scripts can also be executed without directly invoking the powershell.exe binary through interfaces to PowerShell's underlying System.Management.Automation assembly DLL exposed through the .NET framework and Windows Common Language Interface (CLI).[3][4][5]

Adversaries may gain persistence and elevate privileges by executing malicious content triggered by PowerShell profiles. A PowerShell profile (profile.ps1) is a script that runs when PowerShell starts and can be used as a logon script to customize user environments.

PowerShell supports several profiles depending on the user or host program. For example, there can be different profiles for PowerShell host programs such as the PowerShell console, PowerShell ISE or Visual Studio Code. An administrator can also configure a profile that applies to all users and host programs on the local computer. [1]

Adversaries may modify these profiles to include arbitrary commands, functions, modules, and/or PowerShell drives to gain persistence. Every time a user opens a PowerShell session the modified script will be executed unless the -NoProfile flag is used when it is launched. [2]

An adversary may also be able to escalate privileges if a script in a PowerShell profile is loaded and executed by an account with higher privileges, such as a domain administrator. [3]

Adversaries may abuse Pre-OS Boot mechanisms as a way to establish persistence on a system. During the booting process of a computer, firmware and various startup services are loaded before the operating system. These programs control flow of execution before the operating system takes control.[1]

Adversaries may overwrite data in boot drivers or firmware such as BIOS (Basic Input/Output System) and The Unified Extensible Firmware Interface (UEFI) to persist on systems at a layer below the operating system. This can be particularly difficult to detect as malware at this level will not be detected by host software-based defenses.

Adversaries may abuse the Android device administration API to prevent the user from uninstalling a target application. In earlier versions of Android, device administrator applications needed their administration capabilities explicitly deactivated by the user before the application could be uninstalled. This was later updated so the user could deactivate and uninstall the administrator application in one step.

Adversaries may also abuse the device accessibility APIs to prevent removal. This set of APIs allows the application to perform certain actions on behalf of the user and programmatically determine what is being shown on the screen. The malicious application could monitor the device screen for certain modals (e.g., the confirmation modal to uninstall an application) and inject screen input or a back button tap to close the modal. For example, Android's `performGlobalAction(int)` API could be utilized to prevent the user from removing the malicious application from the device after installation. If the user wants to uninstall the malicious application, two cases may occur, both preventing the user from removing the application.

* Case 1: If the integer argument passed to the API call is `2` or `GLOBAL_ACTION_HOME`, the malicious application may direct the user to the home screen from settings screen

* Case 2: If the integer argument passed to the API call is `1` or `GLOBAL_ACTION_BACK`, the malicious application may emulate the back press event

Adversaries may impair command history logging to hide commands they run on a compromised system. Various command interpreters keep track of the commands users type in their terminal so that users can retrace what they have done.

On Linux and macOS, command history is tracked in a file pointed to by the environment variable `HISTFILE`. When a user logs off a system, this information is flushed to a file in the user's home directory called `~/.bash_history`. The `HISTCONTROL` environment variable keeps track of what should be saved by the history command and eventually into the `~/.bash_history` file when a user logs out. `HISTCONTROL` does not exist by default on macOS, but can be set by the user and will be respected. The `HISTFILE` environment variable is also used in some ESXi systems.[1]

Adversaries may clear the history environment variable (`unset HISTFILE`) or set the command history size to zero (`export HISTFILESIZE=0`) to prevent logging of commands. Additionally, `HISTCONTROL` can be configured to ignore commands that start with a space by simply setting it to "ignorespace". `HISTCONTROL` can also be set to ignore duplicate commands by setting it to "ignoredups". In some Linux systems, this is set by default to "ignoreboth" which covers both of the previous examples. This means that " ls" will not be saved, but "ls" would be saved by history. Adversaries can abuse this to operate without leaving traces by simply prepending a space to all of their terminal commands.

On Windows systems, the `PSReadLine` module tracks commands used in all PowerShell sessions and writes them to a file (`$env:APPDATA\Microsoft\Windows\PowerShell\PSReadLine\ConsoleHost_history.txt` by default). Adversaries may change where these logs are saved using `Set-PSReadLineOption -HistorySavePath {File Path}`. This will cause `ConsoleHost_history.txt` to stop receiving logs. Additionally, it is possible to turn off logging to this file using the PowerShell command `Set-PSReadlineOption -HistorySaveStyle SaveNothing`.[2][3]

Adversaries may also leverage a Network Device CLI on network devices to disable historical command logging (e.g. `no logging`).

Adversaries may abuse print processors to run malicious DLLs during system boot for persistence and/or privilege escalation. Print processors are DLLs that are loaded by the print spooler service, `spoolsv.exe`, during boot.[1]

Adversaries may abuse the print spooler service by adding print processors that load malicious DLLs at startup. A print processor can be installed through the AddPrintProcessor API call with an account that has SeLoadDriverPrivilege enabled. Alternatively, a print processor can be registered to the print spooler service by adding the HKLM\SYSTEM\\[CurrentControlSet or ControlSet001]\Control\Print\Environments\\[Windows architecture: e.g., Windows x64]\Print Processors\\[user defined]\Driver Registry key that points to the DLL.

For the malicious print processor to be correctly installed, the payload must be located in the dedicated system print-processor directory, that can be found with the GetPrintProcessorDirectory API call, or referenced via a relative path from this directory.[2] After the print processors are installed, the print spooler service, which starts during boot, must be restarted in order for them to run.[3]

The print spooler service runs under SYSTEM level permissions, therefore print processors installed by an adversary may run under elevated privileges.

Adversaries may search for private key certificate files on compromised systems for insecurely stored credentials. Private cryptographic keys and certificates are used for authentication, encryption/decryption, and digital signatures.[1] Common key and certificate file extensions include: .key, .pgp, .gpg, .ppk., .p12, .pem, .pfx, .cer, .p7b, .asc.

Adversaries may also look in common key directories, such as ~/.ssh for SSH keys on * nix-based systems or C:\Users\(username)\.ssh\ on Windows. Adversary tools may also search compromised systems for file extensions relating to cryptographic keys and certificates.[2][3]

When a device is registered to Entra ID, a device key and a transport key are generated and used to verify the device’s identity.[4] An adversary with access to the device may be able to export the keys in order to impersonate the device.[5]

On network devices, private keys may be exported via Network Device CLI commands such as `crypto pki export`.[6]

Some private keys require a password or passphrase for operation, so an adversary may also use Input Capture for keylogging or attempt to Brute Force the passphrase off-line. These private keys can be used to authenticate to Remote Services like SSH or for use in decrypting other collected files such as email.