Techniques

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 enable remote service abuse. A common goal for post-compromise exploitation of remote services is for initial access into and lateral movement throughout the ICS environment to enable access to targeted systems. [1]

ICS asset owners and operators have been affected by ransomware (or disruptive malware masquerading as ransomware) migrating from enterprise IT to ICS environments: WannaCry, NotPetya, and BadRabbit. In each of these cases, self-propagating (wormable) malware initially infected IT networks, but through exploit (particularly the SMBv1-targeting MS17-010 vulnerability) spread to industrial networks, producing significant impacts. [2]

Adversaries may develop exploits that can be used during targeting. An exploit takes advantage of a bug or vulnerability in order to cause unintended or unanticipated behavior to occur on computer hardware or software. Rather than finding/modifying exploits from online or purchasing them from exploit vendors, an adversary may develop their own exploits.[1] Adversaries may use information acquired via Vulnerabilities to focus exploit development efforts. As part of the exploit development process, adversaries may uncover exploitable vulnerabilities through methods such as fuzzing and patch analysis.[2]

As with legitimate development efforts, different skill sets may be required for developing exploits. The skills needed may be located in-house, or may need to be contracted out. Use of a contractor may be considered an extension of that adversary's exploit development capabilities, provided the adversary plays a role in shaping requirements and maintains an initial degree of exclusivity to the exploit.

Adversaries may use exploits during various phases of the adversary lifecycle (i.e. Exploit Public-Facing Application, Exploitation for Client Execution, Exploitation for Privilege Escalation, Exploitation for Stealth, Exploitation for Credential Access, Exploitation of Remote Services, and Application or System Exploitation).

Adversaries may buy, steal, or download exploits that can be used during targeting. An exploit takes advantage of a bug or vulnerability in order to cause unintended or unanticipated behavior to occur on computer hardware or software. Rather than developing their own exploits, an adversary may find/modify exploits from online or purchase them from exploit vendors.[1][2][3]

In addition to downloading free exploits from the internet, adversaries may purchase exploits from third-party entities. Third-party entities can include technology companies that specialize in exploit development, criminal marketplaces (including exploit kits), or from individuals.[4][5] In addition to purchasing exploits, adversaries may steal and repurpose exploits from third-party entities (including other adversaries).[2]

An adversary may monitor exploit provider forums to understand the state of existing, as well as newly discovered, exploits. There is usually a delay between when an exploit is discovered and when it is made public. An adversary may target the systems of those known to conduct exploit research and development in order to gain that knowledge for use during a subsequent operation.

Adversaries may use exploits during various phases of the adversary lifecycle (i.e. Exploit Public-Facing Application, Exploitation for Client Execution, Exploitation for Privilege Escalation, Exploitation for Stealth, Exploitation for Credential Access, Exploitation of Remote Services, and Application or System Exploitation).

Adversaries may abuse extended attributes (xattrs) on macOS and Linux to hide their malicious data in order to evade detection. Extended attributes are key-value pairs of file and directory metadata used by both macOS and Linux. They are not visible through standard tools like `Finder`, `ls`, or `cat` and require utilities such as `xattr` (macOS) or `getfattr` (Linux) for inspection. Operating systems and applications use xattrs for tagging, integrity checks, and access control. On Linux, xattrs are organized into namespaces such as `user.` (user permissions), `trusted.` (root permissions), `security.`, and `system.`, each with specific permissions. On macOS, xattrs are flat strings without namespace prefixes, commonly prefixed with `com.apple.*` (e.g., `com.apple.quarantine`, `com.apple.metadata:_kMDItemUserTags`) and used by system features like Gatekeeper and Spotlight.[1]

An adversary may leverage xattrs by embedding a second-stage payload into the extended attribute of a legitimate file. On macOS, a payload can be embedded into a custom attribute using the `xattr` command. A separate loader can retrieve the attribute with `xattr -p`, decode the content, and execute it using a scripting interpreter. On Linux, an adversary may use `setfattr` to write a payload into the `user.` namespace of a legitimate file. A loader script can later extract the payload with `getfattr --only-values`, decode it, and execute it using bash or another interpreter. In both cases, because the primary file content remains unchanged, security tools and integrity checks that do not inspect extended attributes will observe the original file hash, allowing the malicious payload to evade detection.[2]

An adversary may deface systems external to an organization in an attempt to deliver messaging, intimidate, or otherwise mislead an organization or users. External Defacement may ultimately cause users to distrust the systems and to question/discredit the system’s integrity. Externally-facing websites are a common victim of defacement; often targeted by adversary and hacktivist groups in order to push a political message or spread propaganda.[1][2][3] External Defacement may be used as a catalyst to trigger events, or as a response to actions taken by an organization or government. Similarly, website defacement may also be used as setup, or a precursor, for future attacks such as Drive-by Compromise.[4]

Adversaries may use an external proxy to act as an intermediary for network communications to a command and control server to avoid direct connections to their infrastructure. Many tools exist that enable traffic redirection through proxies or port redirection, including HTRAN, ZXProxy, and ZXPortMap. [1] Adversaries use these types of proxies to manage command and control communications, to provide resiliency in the face of connection loss, or to ride over existing trusted communications paths to avoid suspicion.

External connection proxies are used to mask the destination of C2 traffic and are typically implemented with port redirectors. Compromised systems outside of the victim environment may be used for these purposes, as well as purchased infrastructure such as cloud-based resources or virtual private servers. Proxies may be chosen based on the low likelihood that a connection to them from a compromised system would be investigated. Victim systems would communicate directly with the external proxy on the Internet and then the proxy would forward communications to the C2 server.

Adversaries may leverage external-facing remote services to initially access and/or persist within a network. Remote services such as VPNs, Citrix, and other access mechanisms allow users to connect to internal enterprise network resources from external locations. There are often remote service gateways that manage connections and credential authentication for these services. Services such as Windows Remote Management and VNC can also be used externally.[1]

Access to Valid Accounts to use the service is often a requirement, which could be obtained through credential pharming or by obtaining the credentials from users after compromising the enterprise network.[2] Access to remote services may be used as a redundant or persistent access mechanism during an operation.

Access may also be gained through an exposed service that doesn’t require authentication. In containerized environments, this may include an exposed Docker API, Kubernetes API server, kubelet, or web application such as the Kubernetes dashboard.[3][4]

Adversaries may also establish persistence on network by configuring a Tor hidden service on a compromised system. Adversaries may utilize the tool `ShadowLink` to facilitate the installation and configuration of the Tor hidden service. Tor hidden service is then accessible via the Tor network because `ShadowLink` sets up a .onion address on the compromised system. `ShadowLink` may be used to forward any inbound connections to RDP, allowing the adversaries to have remote access.[5] Adversaries may get `ShadowLink` to persist on a system by masquerading it as an MS Defender application.[6]

Adversaries may leverage external remote services as a point of initial access into your network. These services allow users to connect to internal network resources from external locations. Examples are VPNs, Citrix, and other access mechanisms. Remote service gateways often manage connections and credential authentication for these services. [1]

External remote services allow administration of a control system from outside the system. Often, vendors and internal engineering groups have access to external remote services to control system networks via the corporate network. In some cases, this access is enabled directly from the internet. While remote access enables ease of maintenance when a control system is in a remote area, compromise of remote access solutions is a liability. The adversary may use these services to gain access to and execute attacks against a control system network. Access to valid accounts is often a requirement.

As they look for an entry point into the control system network, adversaries may begin searching for existing point-to-point VPN implementations at trusted third party networks or through remote support employee connections where split tunneling is enabled. [2]

Adversaries may inject malicious code into process via Extra Window Memory (EWM) in order to evade process-based defenses as well as possibly elevate privileges. EWM injection is a method of executing arbitrary code in the address space of a separate live process.

Before creating a window, graphical Windows-based processes must prescribe to or register a windows class, which stipulate appearance and behavior (via windows procedures, which are functions that handle input/output of data).[1] Registration of new windows classes can include a request for up to 40 bytes of EWM to be appended to the allocated memory of each instance of that class. This EWM is intended to store data specific to that window and has specific application programming interface (API) functions to set and get its value. [2] [3]

Although small, the EWM is large enough to store a 32-bit pointer and is often used to point to a windows procedure. Malware may possibly utilize this memory location in part of an attack chain that includes writing code to shared sections of the process’s memory, placing a pointer to the code in EWM, then invoking execution by returning execution control to the address in the process’s EWM.

Execution granted through EWM injection may allow access to both the target process's memory and possibly elevated privileges. Writing payloads to shared sections also avoids the use of highly monitored API calls such as WriteProcessMemory and CreateRemoteThread.[4] More sophisticated malware samples may also potentially bypass protection mechanisms such as data execution prevention (DEP) by triggering a combination of windows procedures and other system functions that will rewrite the malicious payload inside an executable portion of the target process. [5] [6]

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

Adversaries may use fallback or alternate communication channels if the primary channel is compromised or inaccessible in order to maintain reliable command and control and to avoid data transfer thresholds.

Adversaries may use Fast Flux DNS to hide a command and control channel behind an array of rapidly changing IP addresses linked to a single domain resolution. This technique uses a fully qualified domain name, with multiple IP addresses assigned to it which are swapped with high frequency, using a combination of round robin IP addressing and short Time-To-Live (TTL) for a DNS resource record.[1][2][3]

The simplest, "single-flux" method, involves registering and de-registering an addresses as part of the DNS A (address) record list for a single DNS name. These registrations have a five-minute average lifespan, resulting in a constant shuffle of IP address resolution.[3]

In contrast, the "double-flux" method registers and de-registers an address as part of the DNS Name Server record list for the DNS zone, providing additional resilience for the connection. With double-flux additional hosts can act as a proxy to the C2 host, further insulating the true source of the C2 channel.

Adversaries may delete files left behind by the actions of their intrusion activity. Malware, tools, or other non-native files dropped or created on a system by an adversary (ex: Ingress Tool Transfer) may leave traces to indicate to what was done within a network and how. Removal of these files can occur during an intrusion, or as part of a post-intrusion process to minimize the adversary's footprint.

There are tools available from the host operating system to perform cleanup, but adversaries may use other tools as well.[1] Examples of built-in Command and Scripting Interpreter functions include del on Windows, rm or unlink on Linux and macOS, and `rm` on ESXi.

Adversaries may wipe a device or delete individual files in order to manipulate external outcomes or hide activity. An application must have administrator access to fully wipe the device, while individual files may not require special permissions to delete depending on their storage location.[1]

Stored data could include a variety of file formats, such as Office files, databases, stored emails, and custom file formats. The impact file deletion will have depends on the type of data as well as the goals and objectives of the adversary, but can include deleting update files to evade detection or deleting attacker-specified files for impact.

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

Protocols such as SMB[1], FTP[2], FTPS, and TFTP that transfer files may be very common in environments. Packets produced from these protocols may have many fields and headers in which data can be concealed. Data could also be concealed within the transferred files. An adversary may abuse these protocols to communicate with systems under their control within a victim network while also mimicking normal, expected traffic.

Adversaries may enumerate files and directories or may search in specific locations of a host or network share for certain information within a file system. Adversaries may use the information from File and Directory Discovery during automated discovery to shape follow-on behaviors, including whether or not the adversary fully infects the target and/or attempts specific actions.

Many command shell utilities can be used to obtain this information. Examples include dir, tree, ls, find, and locate.[1] Custom tools may also be used to gather file and directory information and interact with the Native API. Adversaries may also leverage a Network Device CLI on network devices to gather file and directory information (e.g. dir, show flash, and/or nvram).[2]

Some files and directories may require elevated or specific user permissions to access.

Adversaries may enumerate files and directories or search in specific device locations for desired information within a filesystem. Adversaries may use the information from File and Directory Discovery during automated discovery to shape follow-on behaviors, including deciding if the adversary should fully infect the target and/or attempt specific actions.

On Android, Linux file permissions and SELinux policies typically stringently restrict what can be accessed by apps without taking advantage of a privilege escalation exploit. The contents of the external storage directory are generally visible, which could present concerns if sensitive data is inappropriately stored there. iOS's security architecture generally restricts the ability to perform any type of File and Directory Discovery without use of escalated privileges.

Adversaries may modify file or directory permissions/attributes to evade access control lists (ACLs) and access protected files.[1][2] File and directory permissions are commonly managed by ACLs configured by the file or directory owner, or users with the appropriate permissions. File and directory ACL implementations vary by platform, but generally explicitly designate which users or groups can perform which actions (read, write, execute, etc.).

Modifications may include changing specific access rights, which may require taking ownership of a file or directory and/or elevated permissions depending on the file or directory’s existing permissions. This may enable malicious activity such as modifying, replacing, or deleting specific files or directories. Specific file and directory modifications may be a required step for many techniques, such as establishing Persistence via Accessibility Features, Boot or Logon Initialization Scripts, Unix Shell Configuration Modification, or tainting/hijacking other instrumental binary/configuration files via Hijack Execution Flow.

Adversaries may also change permissions of symbolic links. For example, malware (particularly ransomware) may modify symbolic links and associated settings to enable access to files from local shortcuts with remote paths.[3][4][5][6][7]

Adversaries may attempt to hide their file-based artifacts by writing them to specific folders or file names excluded from antivirus (AV) scanning and other defensive capabilities. AV and other file-based scanners often include exclusions to optimize performance as well as ease installation and legitimate use of applications. These exclusions may be contextual (e.g., scans are only initiated in response to specific triggering events/alerts), but are also often hardcoded strings referencing specific folders and/or files assumed to be trusted and legitimate.[1]

Adversaries may abuse these exclusions to hide their file-based artifacts. For example, rather than tampering with tool settings to add a new exclusion (i.e., Disable or Modify Tools), adversaries may drop their file-based payloads in default or otherwise well-known exclusions. Adversaries may also use Security Software Discovery and other Discovery/Reconnaissance activities to both discover and verify existing exclusions in a victim environment.

Adversaries may store data in "fileless" formats to conceal malicious activity from defenses. Fileless storage can be broadly defined as any format other than a file. Common examples of non-volatile fileless storage in Windows systems include the Windows Registry, event logs, or WMI repository.[1][2] Shared memory directories on Linux systems (`/dev/shm`, `/run/shm`, `/var/run`, and `/var/lock`) and volatile directories on Network Devices (`/tmp` and `/volatile`) may also be considered fileless storage, as files written to these directories are mapped directly to RAM and not stored on the disk.[3][4][5][6][7].

Similar to fileless in-memory behaviors such as Reflective Code Loading and Process Injection, fileless data storage may remain undetected by antivirus and other endpoint security tools that can only access specific file formats from disk storage. Leveraging fileless storage may also allow adversaries to bypass the protections offered by read-only file systems in Linux.[8]

Adversaries may use fileless storage to conceal various types of stored data, including payloads/shellcode (potentially being used as part of Persistence) and collected data not yet exfiltrated from the victim (e.g., Local Data Staging). Adversaries also often encrypt, encode, splice, or otherwise obfuscate this fileless data when stored.

Some forms of fileless storage activity may indirectly create artifacts in the file system, but in central and otherwise difficult to inspect formats such as the WMI (e.g., `%SystemRoot%\System32\Wbem\Repository`) or Registry (e.g., `%SystemRoot%\System32\Config`) physical files.[1]

Adversaries may steal monetary resources from targets through extortion, social engineering, technical theft, or other methods aimed at their own financial gain at the expense of the availability of these resources for victims. Financial theft is the ultimate objective of several popular campaign types including extortion by ransomware,[1] business email compromise (BEC) and fraud,[2] "pig butchering,"[3] bank hacking,[4] and exploiting cryptocurrency networks.[5]

Adversaries may Compromise Accounts to conduct unauthorized transfers of funds.[6] In the case of business email compromise or email fraud, an adversary may utilize Impersonation of a trusted entity. Once the social engineering is successful, victims can be deceived into sending money to financial accounts controlled by an adversary.[2] This creates the potential for multiple victims (i.e., compromised accounts as well as the ultimate monetary loss) in incidents involving financial theft.[7]

Extortion by ransomware may occur, for example, when an adversary demands payment from a victim after Data Encrypted for Impact [8] and Exfiltration of data, followed by threatening to leak sensitive data to the public unless payment is made to the adversary.[9] Adversaries may use dedicated leak sites to distribute victim data.[10]

Due to the potentially immense business impact of financial theft, an adversary may abuse the possibility of financial theft and seeking monetary gain to divert attention from their true goals such as Data Destruction and business disruption.[11]

Adversaries may gather information about the victim's host firmware that can be used during targeting. Information about host firmware may include a variety of details such as type and versions on specific hosts, which may be used to infer more information about hosts in the environment (ex: configuration, purpose, age/patch level, etc.).

Adversaries may gather this information in various ways, such as direct elicitation via Phishing for Information. Information about host firmware may only be exposed to adversaries via online or other accessible data sets (ex: job postings, network maps, assessment reports, resumes, or purchase invoices).[1] Gathering this information may reveal opportunities for other forms of reconnaissance (ex: Search Open Websites/Domains or Search Open Technical Databases), establishing operational resources (ex: Develop Capabilities or Obtain Capabilities), and/or initial access (ex: Supply Chain Compromise or Exploit Public-Facing Application).

Adversaries may overwrite or corrupt the flash memory contents of system BIOS or other firmware in devices attached to a system in order to render them inoperable or unable to boot, thus denying the availability to use the devices and/or the system.[1] Firmware is software that is loaded and executed from non-volatile memory on hardware devices in order to initialize and manage device functionality. These devices may include the motherboard, hard drive, or video cards.

In general, adversaries may manipulate, overwrite, or corrupt firmware in order to deny the use of the system or devices. For example, corruption of firmware responsible for loading the operating system for network devices may render the network devices inoperable.[2][3] Depending on the device, this attack may also result in Data Destruction.

Adversaries may gather credential material by invoking or forcing a user to automatically provide authentication information through a mechanism in which they can intercept.

The Server Message Block (SMB) protocol is commonly used in Windows networks for authentication and communication between systems for access to resources and file sharing. When a Windows system attempts to connect to an SMB resource it will automatically attempt to authenticate and send credential information for the current user to the remote system.[1] This behavior is typical in enterprise environments so that users do not need to enter credentials to access network resources.

Web Distributed Authoring and Versioning (WebDAV) is also typically used by Windows systems as a backup protocol when SMB is blocked or fails. WebDAV is an extension of HTTP and will typically operate over TCP ports 80 and 443.[2][3]

Adversaries may take advantage of this behavior to gain access to user account hashes through forced SMB/WebDAV authentication. An adversary can send an attachment to a user through spearphishing that contains a resource link to an external server controlled by the adversary (i.e. Template Injection), or place a specially crafted file on navigation path for privileged accounts (e.g. .SCF file placed on desktop) or on a publicly accessible share to be accessed by victim(s). When the user's system accesses the untrusted resource, it will attempt authentication and send information, including the user's hashed credentials, over SMB to the adversary-controlled server.[4] With access to the credential hash, an adversary can perform off-line Brute Force cracking to gain access to plaintext credentials.[5]

There are several different ways this can occur.[6] Some specifics from in-the-wild use include:

* A spearphishing attachment containing a document with a resource that is automatically loaded when the document is opened (i.e. Template Injection). The document can include, for example, a request similar to file[:]//[remote address]/Normal.dotm to trigger the SMB request.[7] * A modified .LNK or .SCF file with the icon filename pointing to an external reference such as \\[remote address]\pic.png that will force the system to load the resource when the icon is rendered to repeatedly gather credentials.[7]

Alternatively, by leveraging the EfsRpcOpenFileRaw function, an adversary can send SMB requests to a remote system's MS-EFSRPC interface and force the victim computer to initiate an authentication procedure and share its authentication details. The Encrypting File System Remote Protocol (EFSRPC) is a protocol used in Windows networks for maintenance and management operations on encrypted data that is stored remotely to be accessed over a network. Utilization of EfsRpcOpenFileRaw function in EFSRPC is used to open an encrypted object on the server for backup or restore. Adversaries can collect this data and abuse it as part of a NTLM relay attack to gain access to remote systems on the same internal network.[8][9]

Adversaries may abuse Android's `startForeground()` API method to maintain continuous sensor access. Beginning in Android 9, idle applications running in the background no longer have access to device sensors, such as the camera, microphone, and gyroscope.[1] Applications can retain sensor access by running in the foreground, using Android’s `startForeground()` API method. This informs the system that the user is actively interacting with the application, and it should not be killed. The only requirement to start a foreground service is showing a persistent notification to the user.[2]

Malicious applications may abuse the `startForeground()` API method to continue running in the foreground, while presenting a notification to the user pretending to be a genuine application. This would allow unhindered access to the device’s sensors, assuming permission has been previously granted.[3]

Malicious applications may also abuse the `startForeground()` API to inform the Android system that the user is actively interacting with the application, thus preventing it from being killed by the low memory killer.[4]

Adversaries may forge credential materials that can be used to gain access to web applications or Internet services. Web applications and services (hosted in cloud SaaS environments or on-premise servers) often use session cookies, tokens, or other materials to authenticate and authorize user access.

Adversaries may generate these credential materials in order to gain access to web resources. This differs from Steal Web Session Cookie, Steal Application Access Token, and other similar behaviors in that the credentials are new and forged by the adversary, rather than stolen or intercepted from legitimate users.

The generation of web credentials often requires secret values, such as passwords, Private Keys, or other cryptographic seed values.[1] Adversaries may also forge tokens by taking advantage of features such as the `AssumeRole` and `GetFederationToken` APIs in AWS, which allow users to request temporary security credentials (i.e., Temporary Elevated Cloud Access), or the `zmprov gdpak` command in Zimbra, which generates a pre-authentication key that can be used to generate tokens for any user in the domain.[2][3]

Once forged, adversaries may use these web credentials to access resources (ex: Use Alternate Authentication Material), which may bypass multi-factor and other authentication protection mechanisms.[4][5][6]