Techniques

Adversaries may attempt to exfiltrate data over a different network medium than the command and control channel. If the command and control network is a wired Internet connection, the exfiltration may occur, for example, over a WiFi connection, modem, cellular data connection, Bluetooth, or another radio frequency (RF) channel.

Adversaries may choose to do this if they have sufficient access or proximity, and the connection might not be secured or defended as well as the primary Internet-connected channel because it is not routed through the same enterprise network.

Adversaries may attempt to exfiltrate data via a physical medium, such as a removable drive. In certain circumstances, such as an air-gapped network compromise, exfiltration could occur via a physical medium or device introduced by a user. Such media could be an external hard drive, USB drive, cellular phone, MP3 player, or other removable storage and processing device. The physical medium or device could be used as the final exfiltration point or to hop between otherwise disconnected systems.

Adversaries may steal data by exfiltrating it over a symmetrically encrypted network protocol other than that of the existing command and control channel. The data may also be sent to an alternate network location from the main command and control server.

Symmetric encryption algorithms are those that use shared or the same keys/secrets on each end of the channel. This requires an exchange or pre-arranged agreement/possession of the value used to encrypt and decrypt data.

Network protocols that use asymmetric encryption often utilize symmetric encryption once keys are exchanged, but adversaries may opt to manually share keys and implement symmetric cryptographic algorithms (ex: RC4, AES) vice using mechanisms that are baked into a protocol. This may result in multiple layers of encryption (in protocols that are natively encrypted such as HTTPS) or encryption in protocols that not typically encrypted (such as HTTP or FTP).

Adversaries may steal data by exfiltrating it over an un-encrypted network protocol other than that of the existing command and control channel. The data may also be sent to an alternate network location from the main command and control server.[1]

Adversaries may opt to obfuscate this data, without the use of encryption, within network protocols that are natively unencrypted (such as HTTP, FTP, or DNS). This may include custom or publicly available encoding/compression algorithms (such as base64) as well as embedding data within protocol headers and fields.

Adversaries may steal data by exfiltrating it over an un-encrypted network protocol other than that of the existing command and control channel. The data may also be sent to an alternate network location from the main command and control server.

Adversaries may opt to obfuscate this data, without the use of encryption, within network protocols that are natively unencrypted (such as HTTP, FTP, or DNS). Adversaries may employ custom or publicly available encoding/compression algorithms (such as base64) or embed data within protocol headers and fields.

Adversaries may use an existing, legitimate external Web service to exfiltrate data rather than their primary command and control channel. Popular Web services acting as an exfiltration mechanism may give a significant amount of cover due to the likelihood that hosts within a network are already communicating with them prior to compromise. Firewall rules may also already exist to permit traffic to these services.

Web service providers also commonly use SSL/TLS encryption, giving adversaries an added level of protection.

Adversaries may exfiltrate data to a webhook endpoint rather than over their primary command and control channel. Webhooks are simple mechanisms for allowing a server to push data over HTTP/S to a client without the need for the client to continuously poll the server.[1] Many public and commercial services, such as Discord, Slack, and `webhook.site`, support the creation of webhook endpoints that can be used by other services, such as Github, Jira, or Trello.[2] When changes happen in the linked services (such as pushing a repository update or modifying a ticket), these services will automatically post the data to the webhook endpoint for use by the consuming application.

Adversaries may link an adversary-owned environment to a victim-owned SaaS service to achieve repeated Automated Exfiltration of emails, chat messages, and other data.[3] Alternatively, instead of linking the webhook endpoint to a service, an adversary can manually post staged data directly to the URL in order to exfiltrate it.[4]

Access to webhook endpoints is often over HTTPS, which gives the adversary an additional level of protection. Exfiltration leveraging webhooks can also blend in with normal network traffic if the webhook endpoint points to a commonly used SaaS application or collaboration service.[5][6][7]

Adversaries may attempt to exfiltrate data over a USB connected physical device. In certain circumstances, such as an air-gapped network compromise, exfiltration could occur via a USB device introduced by a user. The USB device could be used as the final exfiltration point or to hop between otherwise disconnected systems.

Adversaries may exfiltrate data to a cloud storage service rather than over their primary command and control channel. Cloud storage services allow for the storage, edit, and retrieval of data from a remote cloud storage server over the Internet.

Examples of cloud storage services include Dropbox and Google Docs. Exfiltration to these cloud storage services can provide a significant amount of cover to the adversary if hosts within the network are already communicating with the service.

Adversaries may exfiltrate data to a code repository rather than over their primary command and control channel. Code repositories are often accessible via an API (ex: https://api.github.com). Access to these APIs are often over HTTPS, which gives the adversary an additional level of protection.

Exfiltration to a code repository can also provide a significant amount of cover to the adversary if it is a popular service already used by hosts within the network.

Adversaries may exfiltrate data to text storage sites instead of their primary command and control channel. Text storage sites, such as pastebin[.]com, are commonly used by developers to share code and other information.

Text storage sites are often used to host malicious code for C2 communication (e.g., Stage Capabilities), but adversaries may also use these sites to exfiltrate collected data. Furthermore, paid features and encryption options may allow adversaries to conceal and store data more securely.[1]

**Note:** This is distinct from Exfiltration to Code Repository, which highlight access to code repositories via APIs.

Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network. The weakness in the system can be a software bug, a temporary glitch, or a misconfiguration.

Exploited applications are often websites/web servers, but can also include databases (like SQL), standard services (like SMB or SSH), network device administration and management protocols (like SNMP and Smart Install), and any other system with Internet-accessible open sockets.[1][2][3][4][5] On ESXi infrastructure, adversaries may exploit exposed OpenSLP services; they may alternatively exploit exposed VMware vCenter servers.[6][7] Depending on the flaw being exploited, this may also involve Exploitation for Stealth or Exploitation for Client Execution.

If an application is hosted on cloud-based infrastructure and/or is containerized, then exploiting it may lead to compromise of the underlying instance or container. This can allow an adversary a path to access the cloud or container APIs (e.g., via the Cloud Instance Metadata API), exploit container host access via Escape to Host, or take advantage of weak identity and access management policies.

Adversaries may also exploit edge network infrastructure and related appliances, specifically targeting devices that do not support robust host-based defenses.[8][9]

For websites and databases, the OWASP top 10 and CWE top 25 highlight the most common web-based vulnerabilities.[10][11]

Adversaries may leverage weaknesses to exploit internet-facing software for initial access into an industrial network. Internet-facing software may be user applications, underlying networking implementations, an assets operating system, weak defenses, etc. Targets of this technique may be intentionally exposed for the purpose of remote management and visibility.

An adversary may seek to target public-facing applications as they may provide direct access into an ICS environment or the ability to move into the ICS network. Publicly exposed applications may be found through online tools that scan the internet for open ports and services. Version numbers for the exposed application may provide adversaries an ability to target specific known vulnerabilities. Exposed control protocol or remote access ports found in Commonly Used Port may be of interest by adversaries.

Adversaries may exploit software vulnerabilities in client applications to execute code. Vulnerabilities can exist in software due to unsecure coding practices that can lead to unanticipated behavior. Adversaries can take advantage of certain vulnerabilities through targeted exploitation for the purpose of arbitrary code execution. Oftentimes the most valuable exploits to an offensive toolkit are those that can be used to obtain code execution on a remote system because they can be used to gain access to that system. Users will expect to see files related to the applications they commonly used to do work, so they are a useful target for exploit research and development because of their high utility.

Several types exist:

### Browser-based Exploitation

Web browsers are a common target through Drive-by Compromise and Spearphishing Link. Endpoint systems may be compromised through normal web browsing or from certain users being targeted by links in spearphishing emails to adversary controlled sites used to exploit the web browser. These often do not require an action by the user for the exploit to be executed.

### Office Applications

Common office and productivity applications such as Microsoft Office are also targeted through Phishing. Malicious files will be transmitted directly as attachments or through links to download them. These require the user to open the document or file for the exploit to run.

### Common Third-party Applications

Other applications that are commonly seen or are part of the software deployed in a target network may also be used for exploitation. Applications such as Adobe Reader and Flash, which are common in enterprise environments, have been routinely targeted by adversaries attempting to gain access to systems. Depending on the software and nature of the vulnerability, some may be exploited in the browser or require the user to open a file. For instance, some Flash exploits have been delivered as objects within Microsoft Office documents.

Adversaries may exploit software vulnerabilities in client applications to execute code. Vulnerabilities can exist in software due to insecure coding practices that can lead to unanticipated behavior. Adversaries may take advantage of certain vulnerabilities through targeted exploitation for the purpose of arbitrary code execution. Oftentimes the most valuable exploits to an offensive toolkit are those that can be used to obtain code execution on a remote system because they can be used to gain access to that system. Users will expect to see files related to the applications they commonly used to do work, so they are a useful target for exploit research and development because of their high utility.

Adversaries may use device-based zero-click exploits for code execution. These exploits are powerful because there is no user interaction required for code execution.

### SMS/iMessage Delivery

SMS and iMessage in iOS are common targets through Drive-By Compromise, Phishing, etc. Adversaries may use embed malicious links, files, etc. in SMS messages or iMessages. Mobile devices may be compromised through one-click exploits, where the victim must interact with a text message, or zero-click exploits, where no user interaction is required.

### AirDrop

Unique to iOS, AirDrop is a network protocol that allows iOS users to transfer files between iOS devices. Before patches from Apple were released, on iOS 13.4 and earlier, adversaries may force the Apple Wireless Direct Link (AWDL) interface to activate, then exploit a buffer overflow to gain access to the device and run as root without interaction from the user.

Adversaries may exploit software vulnerabilities in an attempt to collect credentials. Exploitation of a software vulnerability occurs when an adversary takes advantage of a programming error in a program, service, or within the operating system software or kernel itself to execute adversary-controlled code.

Credentialing and authentication mechanisms may be targeted for exploitation by adversaries as a means to gain access to useful credentials or circumvent the process to gain authenticated access to systems. One example of this is `MS14-068`, which targets Kerberos and can be used to forge Kerberos tickets using domain user permissions.[1][2] Another example of this is replay attacks, in which the adversary intercepts data packets sent between parties and then later replays these packets. If services don't properly validate authentication requests, these replayed packets may allow an adversary to impersonate one of the parties and gain unauthorized access or privileges.[3][4][5]

Such exploitation has been demonstrated in cloud environments as well. For example, adversaries have exploited vulnerabilities in public cloud infrastructure that allowed for unintended authentication token creation and renewal.[6]

Exploitation for credential access may also result in Privilege Escalation depending on the process targeted or credentials obtained.

Adversaries may exploit vulnerabilities in security software, infrastructure, or defensive components to degrade, disable, or otherwise continue to impair their ability to prevent, detect, or respond to malicious activity. Adversaries may exploit a system or application vulnerability to directly interfere with defensive mechanisms. Exploitation occurs when an adversary takes advantage of a programming error in software, services, or the operating system to execute adversary-controlled code, often with the goal of weakening or disabling protections.

Vulnerabilities may exist in security tools such as antivirus, endpoint detection and response (EDR), firewalls, or other monitoring solutions. Adversaries may use prior reconnaissance or perform discovery activities (e.g., Software Discovery) to identify defensive tools present in an environment and target them for exploitation.

Successful exploitation may allow adversaries to terminate security processes, disable protections, bypass enforcement mechanisms, or reduce the effectiveness of defensive controls. In some cases, vulnerabilities in cloud-based or SaaS infrastructure may also be leveraged to bypass built-in security boundaries or disrupt visibility and enforcement across environments.[1]

Adversaries may exploit a software vulnerability to take advantage of a programming error in a program, service, or within the operating system software or kernel itself to evade detection. Vulnerabilities may exist in software that can be used to disable or circumvent security features.

Adversaries may have prior knowledge through Remote System Information Discovery about security features implemented on control devices. These device security features will likely be targeted directly for exploitation. There are examples of firmware RAM/ROM consistency checks on control devices being targeted by adversaries to enable the installation of malicious System Firmware.

Adversaries may exploit software vulnerabilities to gain initial access to a mobile device.

This can be accomplished in a variety of ways. Vulnerabilities may be present in the applications, the services, the underlying operating system, or the kernel itself. Several well-known mobile device exploits exist, including FORCEDENTRY, StageFright, and BlueBorne. Furthermore, some exploits may be possible to exploit without any user interaction (i.e. zero-click exploits, see Exploitation for Client Execution), making them particularly dangerous. Mobile operating system vendors are typically very quick to patch such critical bugs, ensuring only a small window where they can be exploited.

Adversaries may exploit software vulnerabilities in an attempt to elevate privileges. Exploitation of a software vulnerability occurs when an adversary takes advantage of a programming error in a program, service, or within the operating system software or kernel itself to execute adversary-controlled code. Security constructs such as permission levels will often hinder access to information and use of certain techniques, so adversaries will likely need to perform privilege escalation to include use of software exploitation to circumvent those restrictions.

When initially gaining access to a system, an adversary may be operating within a lower privileged process which will prevent them from accessing certain resources on the system. Vulnerabilities may exist, usually in operating system components and software commonly running at higher permissions, that can be exploited to gain higher levels of access on the system. This could enable someone to move from unprivileged or user level permissions to SYSTEM or root permissions depending on the component that is vulnerable. This could also enable an adversary to move from a virtualized environment, such as within a virtual machine or container, onto the underlying host. This may be a necessary step for an adversary compromising an endpoint system that has been properly configured and limits other privilege escalation methods.

Adversaries may bring a signed vulnerable driver onto a compromised machine so that they can exploit the vulnerability to execute code in kernel mode. This process is sometimes referred to as Bring Your Own Vulnerable Driver (BYOVD).[1][2] Adversaries may include the vulnerable driver with files delivered during Initial Access or download it to a compromised system via Ingress Tool Transfer or Lateral Tool Transfer.

Adversaries may exploit software vulnerabilities in order to elevate privileges. Exploitation of a software vulnerability occurs when an adversary takes advantage of a programming error in an application, service, within the operating system software, or kernel itself to execute adversary-controlled code. Security constructions, such as permission levels, will often hinder access to information and use of certain techniques. Adversaries will likely need to perform privilege escalation to include use of software exploitation to circumvent those restrictions.

When initially gaining access to a device, an adversary may be operating within a lower privileged process which will prevent them from accessing certain resources on the system. Vulnerabilities may exist, usually in operating system components and applications running at higher permissions, that can be exploited to gain higher levels of access on the system. This could enable someone to move from unprivileged or user- level permission to root permissions depending on the component that is vulnerable.

Adversaries may exploit software vulnerabilities in an attempt to elevate privileges. Exploitation of a software vulnerability occurs when an adversary takes advantage of a programming error in a program, service, or within the operating system software or kernel itself to execute adversary-controlled code. Security constructs such as permission levels will often hinder access to information and use of certain techniques, so adversaries will likely need to perform privilege escalation to include use of software exploitation to circumvent those restrictions. [1]

When initially gaining access to a system, an adversary may be operating within a lower privileged process which will prevent them from accessing certain resources on the system. Vulnerabilities may exist, usually in operating system components and software commonly running at higher permissions, that can be exploited to gain higher levels of access on the system. This could enable someone to move from unprivileged or user level permissions to SYSTEM or root permissions depending on the component that is vulnerable. This may be a necessary step for an adversary compromising an endpoint system that has been properly configured and limits other privilege escalation methods. [1]

Adversaries may exploit vulnerabilities to evade detection by hiding activity, suppressing logging, or operating within trusted or unmonitored components.

Adversaries may exploit a system or application vulnerability to avoid detection while maintaining access within an environment. Exploitation occurs when an adversary leverages a programming flaw to execute code in a manner that minimizes visibility or blends in with legitimate activity.

Rather than directly disabling defenses, adversaries may use exploitation to circumvent monitoring and logging mechanisms. This can include abusing vulnerabilities in logging pipelines, security tools, or cloud infrastructure to evade audit trails, suppress alerts, or operate without generating telemetry.

Adversaries may identify these opportunities through prior reconnaissance or by performing discovery of security controls after initial access. In some cases, vulnerabilities in SaaS or public cloud environments may be exploited to evade logging, obscure activity, or deploy infrastructure that remains hidden from standard monitoring tools.[1][2]

Adversaries may exploit remote services to gain unauthorized access to internal systems once inside of a network. Exploitation of a software vulnerability occurs when an adversary takes advantage of a programming error in a program, service, or within the operating system software or kernel itself to execute adversary-controlled code. A common goal for post-compromise exploitation of remote services is for lateral movement to enable access to a remote system.

An adversary may need to determine if the remote system is in a vulnerable state, which may be done through Network Service Discovery or other Discovery methods looking for common, vulnerable software that may be deployed in the network, the lack of certain patches that may indicate vulnerabilities, or security software that may be used to detect or contain remote exploitation. Servers are likely a high value target for lateral movement exploitation, but endpoint systems may also be at risk if they provide an advantage or access to additional resources.

There are several well-known vulnerabilities that exist in common services such as SMB[1] and RDP[2] as well as applications that may be used within internal networks such as MySQL[3] and web server services.[4][5] Additionally, there have been a number of vulnerabilities in VMware vCenter installations, which may enable threat actors to move laterally from the compromised vCenter server to virtual machines or even to ESXi hypervisors.[6]

Depending on the permissions level of the vulnerable remote service an adversary may achieve Exploitation for Privilege Escalation as a result of lateral movement exploitation as well.

Adversaries may exploit remote services of enterprise servers, workstations, or other resources to gain unauthorized access to internal systems once inside of a network. Adversaries may exploit remote services by taking advantage of a mobile device’s access to an internal enterprise network through local connectivity or through a Virtual Private Network (VPN). Exploitation of a software vulnerability occurs when an adversary takes advantage of a programming error in a program, service, or within the operating system software or kernel itself to execute adversary-controlled code. A common goal for post-compromise exploitation of remote services is for lateral movement to enable access to a remote system.

An adversary may need to determine if the remote system is in a vulnerable state, which may be done through Network Service Scanning or other Discovery methods. These look for common, vulnerable software that may be deployed in the network, the lack of certain patches that may indicate vulnerabilities, or security software that may be used to detect or contain remote exploitation. Servers are likely a high value target for lateral movement exploitation, but endpoint systems may also be at risk if they provide an advantage or access to additional resources.

Depending on the permissions level of the vulnerable remote service, an adversary may achieve Exploitation for Privilege Escalation as a result of lateral movement exploitation as well.