Techniques

Adversaries may add new domain trusts, modify the properties of existing domain trusts, or otherwise change the configuration of trust relationships between domains and tenants to evade defenses and/or elevate privileges.Trust details, such as whether or not user identities are federated, allow authentication and authorization properties to apply between domains or tenants for the purpose of accessing shared resources.[1] These trust objects may include accounts, credentials, and other authentication material applied to servers, tokens, and domains.

Manipulating these trusts may allow an adversary to escalate privileges and/or evade defenses by modifying settings to add objects which they control. For example, in Microsoft Active Directory (AD) environments, this may be used to forge SAML Tokens without the need to compromise the signing certificate to forge new credentials. Instead, an adversary can manipulate domain trusts to add their own signing certificate. An adversary may also convert an AD domain to a federated domain using Active Directory Federation Services (AD FS), which may enable malicious trust modifications such as altering the claim issuance rules to log in any valid set of credentials as a specified user.[2]

An adversary may also add a new federated identity provider to an identity tenant such as Okta or AWS IAM Identity Center, which may enable the adversary to authenticate as any user of the tenant.[3] This may enable the threat actor to gain broad access into a variety of cloud-based services that leverage the identity tenant. For example, in AWS environments, an adversary that creates a new identity provider for an AWS Organization will be able to federate into all of the AWS Organization member accounts without creating identities for each of the member accounts.[4]

Adversaries may take advantage of trusted developer utilities to proxy execution of malicious payloads. There are many utilities used for software development related tasks that can be used to execute code in various forms to assist in development, debugging, and reverse engineering.[1][2][3][4] These utilities may often be signed with legitimate certificates that allow them to execute on a system and proxy execution of malicious code through a trusted process that effectively bypasses application control solutions.

Smart App Control is a feature of Windows that blocks applications it considers potentially malicious from running by verifying unsigned applications against a known safe list from a Microsoft cloud service before executing them.[5] However, adversaries may leverage "reputation hijacking" to abuse an operating system’s trust of safe, signed applications that support the execution of arbitrary code. By leveraging Trusted Developer Utilities Proxy Execution to run their malicious code, adversaries may bypass Smart App Control protections.[6]

Adversaries may breach or otherwise leverage organizations who have access to intended victims. Access through trusted third party relationship abuses an existing connection that may not be protected or receives less scrutiny than standard mechanisms of gaining access to a network.

Organizations often grant elevated access to second or third-party external providers in order to allow them to manage internal systems as well as cloud-based environments. Some examples of these relationships include IT services contractors, managed security providers, infrastructure contractors (e.g. HVAC, elevators, physical security). The third-party provider's access may be intended to be limited to the infrastructure being maintained, but may exist on the same network as the rest of the enterprise. As such, Valid Accounts used by the other party for access to internal network systems may be compromised and used.[1]

In Office 365 environments, organizations may grant Microsoft partners or resellers delegated administrator permissions. By compromising a partner or reseller account, an adversary may be able to leverage existing delegated administrator relationships or send new delegated administrator offers to clients in order to gain administrative control over the victim tenant.[2]

Adversaries may register Uniform Resource Identifiers (URIs) to intercept sensitive data.

Applications regularly register URIs with the operating system to act as a response handler for various actions, such as logging into an app using an external account via single sign-on. This allows redirections to that specific URI to be intercepted by the application. If a malicious application were to register for a URI that was already in use by a genuine application, the malicious application may be able to intercept data intended for the genuine application or perform a phishing attack against the genuine application. Intercepted data may include OAuth authorization codes or tokens that could be used by the malicious application to gain access to resources.[1][2]

Adversaries may register Uniform Resource Identifiers (URIs) to intercept sensitive data.

Applications regularly register URIs with the operating system to act as a response handler for various actions, such as logging into an app using an external account via single sign-on. This allows redirections to that specific URI to be intercepted by the application. If an adversary were to register for a URI that was already in use by a genuine application, the adversary may be able to intercept data intended for the genuine application or perform a phishing attack against the genuine application. Intercepted data may include OAuth authorization codes or tokens that could be used by the adversary to gain access to protected resources.[1][2]

An iOS application may be able to maliciously claim a URL scheme, allowing it to intercept calls that are meant for a different application[1][2]. This technique, for example, could be used to capture OAuth authorization codes[3] or to phish user credentials[4].

Adversaries may maintain persistence through executing malicious content triggered using udev rules. Udev is the Linux kernel device manager that dynamically manages device nodes, handles access to pseudo-device files in the `/dev` directory, and responds to hardware events, such as when external devices like hard drives or keyboards are plugged in or removed. Udev uses rule files with `match keys` to specify the conditions a hardware event must meet and `action keys` to define the actions that should follow. Root permissions are required to create, modify, or delete rule files located in `/etc/udev/rules.d/`, `/run/udev/rules.d/`, `/usr/lib/udev/rules.d/`, `/usr/local/lib/udev/rules.d/`, and `/lib/udev/rules.d/`. Rule priority is determined by both directory and by the digit prefix in the rule filename.[1][2]

Adversaries may abuse the udev subsystem by adding or modifying rules in udev rule files to execute malicious content. For example, an adversary may configure a rule to execute their binary each time the pseudo-device file, such as `/dev/random`, is accessed by an application. Although udev is limited to running short tasks and is restricted by systemd-udevd's sandbox (blocking network and filesystem access), attackers may use scripting commands under the action key `RUN+=` to detach and run the malicious content’s process in the background to bypass these controls.[3]

Adversaries may send unauthorized command messages to instruct control system assets to perform actions outside of their intended functionality, or without the logical preconditions to trigger their expected function. Command messages are used in ICS networks to give direct instructions to control systems devices. If an adversary can send an unauthorized command message to a control system, then it can instruct the control systems device to perform an action outside the normal bounds of the device's actions. An adversary could potentially instruct a control systems device to perform an action that will cause an Impact. [1]

In the Dallas Siren incident, adversaries were able to send command messages to activate tornado alarm systems across the city without an impending tornado or other disaster. [2] [3]

Adversaries may send unauthorized messages to ICS systems and devices to evade defenses or manipulate processes. Unauthorized messages can be categorized as either reporting messages that contain telemetry data about the current state of systems, devices, and processes or as command messages which instruct systems and devices on how to operate. By injecting unauthorized messages, adversaries can make it appear as if everything is working correctly when it isn’t, trigger alarms to misdirect personnel or impact processes, and manipulate controls to disrupt processes.[1]

Adversaries may send unauthorized messages in an ICS environment using software found within the environment (living-off-the-land, vendor-specific interfaces, etc.), custom tooling leveraging OT protocols and libraries, or by positioning themselves between systems and devices and injecting messages into the communications such as the case with an Adversary-in-the-Middle attack.

Adversaries may conduct C2 communications over a non-standard port to bypass proxies and firewalls that have been improperly configured.

Adversaries may include functionality in malware that uninstalls the malicious application from the device. This can be achieved by: * Abusing device owner permissions to perform silent uninstallation using device owner API calls. * Abusing root permissions to delete files from the filesystem. * Abusing the accessibility service. This requires sending an intent to the system to request uninstallation, and then abusing the accessibility service to click the proper places on the screen to confirm uninstallation.

Adversaries may include functionality in malware that uninstalls the malicious application from the device. This can be achieved by:

* Abusing device owner permissions to perform silent uninstallation using device owner API calls. * Abusing root permissions to delete files from the filesystem. * Abusing the accessibility service. This requires an intent be sent to the system to request uninstallation, and then abusing the accessibility service to click the proper places on the screen to confirm uninstallation.

Adversaries may abuse Unix shell commands and scripts for execution. Unix shells are the primary command prompt on Linux, macOS, and ESXi systems, though many variations of the Unix shell exist (e.g. sh, ash, bash, zsh, etc.) depending on the specific OS or distribution.[1][2] Unix shells can control every aspect of a system, with certain commands requiring elevated privileges.

Unix shells also support scripts that enable sequential execution of commands as well as other typical programming operations such as conditionals and loops. Common uses of shell scripts include long or repetitive tasks, or the need to run the same set of commands on multiple systems.

Adversaries may abuse Unix shells to execute various commands or payloads. Interactive shells may be accessed through command and control channels or during lateral movement such as with SSH. Adversaries may also leverage shell scripts to deliver and execute multiple commands on victims or as part of payloads used for persistence.

Some systems, such as embedded devices, lightweight Linux distributions, and ESXi servers, may leverage stripped-down Unix shells via Busybox, a small executable that contains a variety of tools, including a simple shell.

Adversaries may abuse Unix shell commands and scripts for execution. Unix shells are the underlying command prompts on Android and iOS devices. Unix shells can control every aspect of a system, with certain commands requiring elevated privileges that are only accessible if the device has been rooted or jailbroken.

Unix shells also support scripts that enable sequential execution of commands as well as other typical programming operations such as conditionals and loops. Common uses of shell scripts include long or repetitive tasks, or the need to run the same set of commands on multiple systems.

Adversaries may abuse Unix shells to execute various commands or payloads. Interactive shells may be accessed through command and control channels or during lateral movement such as with SSH. Adversaries may also leverage shell scripts to deliver and execute multiple commands on victims or as part of payloads used for persistence.

If the device has been rooted or jailbroken, adversaries may locate and invoke a superuser binary to elevate their privileges and interact with the system as the root user. This dangerous level of permissions allows the adversary to run special commands and modify protected system files.

Adversaries may abuse Unix shell commands and scripts for execution. Unix shells are the primary command prompt on Linux, macOS, and ESXi systems, though many variations of the Unix shell exist (e.g. sh, ash, bash, zsh, etc.) depending on the specific OS or distribution.[1][2] Unix shells can control every aspect of a system, with certain commands requiring elevated privileges.

Unix shells also support scripts that enable sequential execution of commands as well as other typical programming operations such as conditionals and loops. Common uses of shell scripts include long or repetitive tasks, or the need to run the same set of commands on multiple systems.

Adversaries may abuse Unix shells to execute various commands or payloads. Interactive shells may be accessed through command and control channels or during lateral movement such as with Remote Services. Adversaries may also leverage shell scripts to deliver and execute multiple commands on victims or as part of payloads used for persistence.

Within Industrial control system networks, workstations, control servers, hypervisors, networking devices, and embedded devices that run on linux platforms may allow for Unix command shell access or stripped-down shells to implement a subset of commands. Industrial automation equipment generally does not offer command shells as a native user interface.

Adversaries may establish persistence through executing malicious commands triggered by a user’s shell. User Unix Shells execute several configuration scripts at different points throughout the session based on events. For example, when a user opens a command-line interface or remotely logs in (such as via SSH) a login shell is initiated. The login shell executes scripts from the system (/etc) and the user’s home directory (~/) to configure the environment. All login shells on a system use /etc/profile when initiated. These configuration scripts run at the permission level of their directory and are often used to set environment variables, create aliases, and customize the user’s environment. When the shell exits or terminates, additional shell scripts are executed to ensure the shell exits appropriately.

Adversaries may attempt to establish persistence by inserting commands into scripts automatically executed by shells. Using bash as an example, the default shell for most GNU/Linux systems, adversaries may add commands that launch malicious binaries into the /etc/profile and /etc/profile.d files.[1][2] These files typically require root permissions to modify and are executed each time any shell on a system launches. For user level permissions, adversaries can insert malicious commands into ~/.bash_profile, ~/.bash_login, or ~/.profile which are sourced when a user opens a command-line interface or connects remotely.[3][4] Since the system only executes the first existing file in the listed order, adversaries have used ~/.bash_profile to ensure execution. Adversaries have also leveraged the ~/.bashrc file which is additionally executed if the connection is established remotely or an additional interactive shell is opened, such as a new tab in the command-line interface.[5][3][6][7] Some malware targets the termination of a program to trigger execution, adversaries can use the ~/.bash_logout file to execute malicious commands at the end of a session.

For macOS, the functionality of this technique is similar but may leverage zsh, the default shell for macOS 10.15+. When the Terminal.app is opened, the application launches a zsh login shell and a zsh interactive shell. The login shell configures the system environment using /etc/profile, /etc/zshenv, /etc/zprofile, and /etc/zlogin.[8][9][10][11] The login shell then configures the user environment with ~/.zprofile and ~/.zlogin. The interactive shell uses the ~/.zshrc to configure the user environment. Upon exiting, /etc/zlogout and ~/.zlogout are executed. For legacy programs, macOS executes /etc/bashrc on startup.

Adversaries may search compromised systems to find and obtain insecurely stored credentials. These credentials can be stored and/or misplaced in many locations on a system, including plaintext files (e.g. Shell History), operating system or application-specific repositories (e.g. Credentials in Registry), or other specialized files/artifacts (e.g. Private Keys).[1]

Adversaries may create cloud instances in unused geographic service regions in order to evade detection. Access is usually obtained through compromising accounts used to manage cloud infrastructure.

Cloud service providers often provide infrastructure throughout the world in order to improve performance, provide redundancy, and allow customers to meet compliance requirements. Oftentimes, a customer will only use a subset of the available regions and may not actively monitor other regions. If an adversary creates resources in an unused region, they may be able to operate undetected.

A variation on this behavior takes advantage of differences in functionality across cloud regions. An adversary could utilize regions which do not support advanced detection services in order to avoid detection of their activity.

An example of adversary use of unused AWS regions is to mine cryptocurrency through Resource Hijacking, which can cost organizations substantial amounts of money over time depending on the processing power used.[1]

Adversaries may upload malware to third-party or adversary controlled infrastructure to make it accessible during targeting. Malicious software can include payloads, droppers, post-compromise tools, backdoors, and a variety of other malicious content. Adversaries may upload malware to support their operations, such as making a payload available to a victim network to enable Ingress Tool Transfer by placing it on an Internet accessible web server.

Malware may be placed on infrastructure that was previously purchased/rented by the adversary (Acquire Infrastructure) or was otherwise compromised by them (Compromise Infrastructure). Malware can also be staged on web services, such as GitHub or Pastebin; hosted on the InterPlanetary File System (IPFS), where decentralized content storage makes the removal of malicious files difficult; or saved on the blockchain as smart contracts, which are resilient against takedowns that would affect traditional infrastructure.[1][2][3][4]

Adversaries may upload backdoored files, such as software packages, application binaries, virtual machine images, or container images, to third-party software stores, package libraries, extension marketplaces, or repositories (ex: GitHub, CNET, AWS Community AMIs, Docker Hub, PyPi, NPM).[5] By chance encounter, victims may directly download/install these backdoored files via User Execution. Masquerading, including typosquatting legitimate software, may increase the chance of users mistakenly executing these files.

Adversaries may upload tools to third-party or adversary controlled infrastructure to make it accessible during targeting. Tools can be open or closed source, free or commercial. Tools can be used for malicious purposes by an adversary, but (unlike malware) were not intended to be used for those purposes (ex: PsExec). Adversaries may upload tools to support their operations, such as making a tool available to a victim network to enable Ingress Tool Transfer by placing it on an Internet accessible web server.

Tools may be placed on infrastructure that was previously purchased/rented by the adversary (Acquire Infrastructure) or was otherwise compromised by them (Compromise Infrastructure).[1] Tools can also be staged on web services, such as an adversary controlled GitHub repo, or on Platform-as-a-Service offerings that enable users to easily provision applications.[2][3][4]

Adversaries can avoid the need to upload a tool by having compromised victim machines download the tool directly from a third-party hosting location (ex: a non-adversary controlled GitHub repo), including the original hosting site of the tool.

Adversaries may use alternate authentication material, such as password hashes, Kerberos tickets, and application access tokens, in order to move laterally within an environment and bypass normal system access controls.

Authentication processes generally require a valid identity (e.g., username) along with one or more authentication factors (e.g., password, pin, physical smart card, token generator, etc.). Alternate authentication material is legitimately generated by systems after a user or application successfully authenticates by providing a valid identity and the required authentication factor(s). Alternate authentication material may also be generated during the identity creation process.[1][2]

Caching alternate authentication material allows the system to verify an identity has successfully authenticated without asking the user to reenter authentication factor(s). Because the alternate authentication must be maintained by the system—either in memory or on disk—it may be at risk of being stolen through Credential Access techniques. By stealing alternate authentication material, adversaries are able to bypass system access controls and authenticate to systems without knowing the plaintext password or any additional authentication factors.

Adversaries may employ various user activity checks to detect and avoid virtualization and analysis environments. This may include changing behaviors based on the results of checks for the presence of artifacts indicative of a virtual machine environment (VME) or sandbox. If the adversary detects a VME, they may alter their malware to disengage from the victim or conceal the core functions of the implant. They may also search for VME artifacts before dropping secondary or additional payloads. Adversaries may use the information learned from Virtualization/Sandbox Evasion during automated discovery to shape follow-on behaviors.[1]

Adversaries may search for user activity on the host based on variables such as the speed/frequency of mouse movements and clicks [2] , browser history, cache, bookmarks, or number of files in common directories such as home or the desktop. Other methods may rely on specific user interaction with the system before the malicious code is activated, such as waiting for a document to close before activating a macro [3] or waiting for a user to double click on an embedded image to activate.[4]

Adversaries may attempt to avoid detection by hiding malicious behavior from the user. By doing this, an adversary’s modifications would most likely remain installed on the device for longer, allowing the adversary to continue to operate on that device.

While there are many ways this can be accomplished, one method is by using the device’s sensors. By utilizing the various motion sensors on a device, such as accelerometer or gyroscope, an application could detect that the device is being interacted with. That way, the application could continue to run while the device is not in use but cease operating while the user is using the device, hiding anything that would indicate malicious activity was ongoing. Accessing the sensors in this way does not require any permissions from the user, so it would be completely transparent.

Adversaries may attempt to avoid detection by hiding malicious behavior from the user. By doing this, an adversary’s modifications would most likely remain installed on the device for longer, allowing the adversary to continue to operate on that device.

While there are many ways this can be accomplished, one method is by using the device’s sensors. By utilizing the various motion sensors on a device, such as accelerometer or gyroscope, an application could detect that the device is being interacted with. That way, the application could continue to run while the device is not in use but cease operating while the user is using the device, hiding anything that would indicate malicious activity was ongoing. Accessing the sensors in this way does not require any permissions from the user, so it would be completely transparent.

An adversary may rely upon specific actions by a user in order to gain execution. Users may be subjected to social engineering to get them to execute malicious code by, for example, opening a malicious document file or link. These user actions will typically be observed as follow-on behavior from forms of Phishing.

While User Execution frequently occurs shortly after Initial Access it may occur at other phases of an intrusion, such as when an adversary places a file in a shared directory or on a user's desktop hoping that a user will click on it. This activity may also be seen shortly after Internal Spearphishing.

Adversaries may also deceive users into performing actions such as:

* Enabling Remote Access Tools, allowing direct control of the system to the adversary * Running malicious JavaScript in their browser, allowing adversaries to Steal Web Session Cookies[1][2] * Downloading and executing malware for User Execution * Coerceing users to copy, paste, and execute malicious code manually[3][4]

For example, tech support scams can be facilitated through Phishing, vishing, or various forms of user interaction. Adversaries can use a combination of these methods, such as spoofing and promoting toll-free numbers or call centers that are used to direct victims to malicious websites, to deliver and execute payloads containing malware or Remote Access Tools.[5]