Techniques

Adversaries may abuse Regsvr32.exe to proxy execution of malicious code. Regsvr32.exe is a command-line program used to register and unregister object linking and embedding controls, including dynamic link libraries (DLLs), on Windows systems. The Regsvr32.exe binary may also be signed by Microsoft. [1]

Malicious usage of Regsvr32.exe may avoid triggering security tools that may not monitor execution of, and modules loaded by, the regsvr32.exe process because of allowlists or false positives from Windows using regsvr32.exe for normal operations. Regsvr32.exe can also be used to specifically bypass application control using functionality to load COM scriptlets to execute DLLs under user permissions. Since Regsvr32.exe is network and proxy aware, the scripts can be loaded by passing a uniform resource locator (URL) to file on an external Web server as an argument during invocation. This method makes no changes to the Registry as the COM object is not actually registered, only executed. [2] This variation of the technique is often referred to as a "Squiblydoo" and has been used in campaigns targeting governments. [3] [4]

Regsvr32.exe can also be leveraged to register a COM Object used to establish persistence via Component Object Model Hijacking. [3]

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

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

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

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

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

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

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

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

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

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

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

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

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

Remote desktop is a common feature in operating systems. It allows a user to log into an interactive session with a system desktop graphical user interface on a remote system. Microsoft refers to its implementation of the Remote Desktop Protocol (RDP) as Remote Desktop Services (RDS). [1] There are other implementations and third-party tools that provide graphical access Remote Services similar to RDS.

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

Adversaries may also perform RDP session hijacking which involves stealing a legitimate user's remote session. Typically, a user is notified when someone else is trying to steal their session and prompted with a question. With System permissions and using Terminal Services Console, c:\windows\system32\tscon.exe [session number to be stolen], an adversary can hijack a session without the need for credentials or prompts to the user. [3] This can be done remotely or locally and with active or disconnected sessions. [4] It can also lead to Remote System Discovery and Privilege Escalation by stealing a Domain Admin or higher privileged account session. All of this can be done by using native Windows commands, but it has also been added as a feature in RedSnarf. [5]

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

Remote desktop is a common feature in operating systems. It allows a user to log into an interactive session with a system desktop graphical user interface on a remote system. Microsoft refers to its implementation of the Remote Desktop Protocol (RDP) as Remote Desktop Services (RDS).[1]

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

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

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

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

Adversaries may take control of preexisting sessions with remote services to move laterally in an environment. Users may use valid credentials to log into a service specifically designed to accept remote connections, such as telnet, SSH, and RDP. When a user logs into a service, a session will be established that will allow them to maintain a continuous interaction with that service.

Adversaries may commandeer these sessions to carry out actions on remote systems. Remote Service Session Hijacking differs from use of Remote Services because it hijacks an existing session rather than creating a new session using Valid Accounts.[1][2]

Adversaries may use Valid Accounts to log into a service that accepts remote connections, such as telnet, SSH, and VNC. The adversary may then perform actions as the logged-on user.

In an enterprise environment, servers and workstations can be organized into domains. Domains provide centralized identity management, allowing users to login using one set of credentials across the entire network. If an adversary is able to obtain a set of valid domain credentials, they could login to many different machines using remote access protocols such as secure shell (SSH) or remote desktop protocol (RDP).[1][2] They could also login to accessible SaaS or IaaS services, such as those that federate their identities to the domain, or management platforms for internal virtualization environments such as VMware vCenter.

Legitimate applications (such as Software Deployment Tools and other administrative programs) may utilize Remote Services to access remote hosts. For example, Apple Remote Desktop (ARD) on macOS is native software used for remote management. ARD leverages a blend of protocols, including VNC to send the screen and control buffers and SSH for secure file transfer.[3][4][5] Adversaries can abuse applications such as ARD to gain remote code execution and perform lateral movement. In versions of macOS prior to 10.14, an adversary can escalate an SSH session to an ARD session which enables an adversary to accept TCC (Transparency, Consent, and Control) prompts without user interaction and gain access to data.[6][7][4]

Adversaries may leverage remote services to move between assets and network segments. These services are often used to allow operators to interact with systems remotely within the network, some examples are RDP, SMB, SSH, and other similar mechanisms. [1] [2] [3]

Remote services could be used to support remote access, data transmission, authentication, name resolution, and other remote functions. Further, remote services may be necessary to allow operators and administrators to configure systems within the network from their engineering or management workstations. An adversary may use this technique to access devices which may be dual-homed [1] to multiple network segments, and can be used for Program Download or to execute attacks on control devices directly through Valid Accounts.

Specific remote services (RDP & VNC) may be a precursor to enable Graphical User Interface execution on devices such as HMIs or engineering workstation software.

Based on incident data, CISA and FBI assessed that Chinese state-sponsored actors also compromised various authorized remote access channels, including systems designed to transfer data and/or allow access between corporate and ICS networks. [4]

Adversaries may attempt to get a listing of other systems by IP address, hostname, or other logical identifier on a network that may be used for Lateral Movement from the current system. Functionality could exist within remote access tools to enable this, but utilities available on the operating system could also be used such as Ping, net view using Net, or, on ESXi servers, `esxcli network diag ping`.

Adversaries may also analyze data from local host files (ex: C:\Windows\System32\Drivers\etc\hosts or /etc/hosts) or other passive means (such as local Arp cache entries) in order to discover the presence of remote systems in an environment.

Adversaries may also target discovery of network infrastructure as well as leverage Network Device CLI commands on network devices to gather detailed information about systems within a network (e.g. show cdp neighbors, show arp).[1][2]

Adversaries may attempt to get a listing of other systems by IP address, hostname, or other logical identifier on a network that may be used for subsequent Lateral Movement or Discovery techniques. Functionality could exist within adversary tools to enable this, but utilities available on the operating system or vendor software could also be used.[1]

An adversary may attempt to get detailed information about remote systems and their peripherals, such as make/model, role, and configuration. Adversaries may use information from Remote System Information Discovery to aid in targeting and shaping follow-on behaviors. For example, the system's operational role and model information can dictate whether it is a relevant target for the adversary's operational objectives. In addition, the system's configuration may be used to scope subsequent technique usage.

Requests for system information are typically implemented using automation and management protocols and are often automatically requested by vendor software during normal operation. This information may be used to tailor management actions, such as program download and system or module firmware. An adversary may leverage this same information by issuing calls directly to the system's API.

An adversary who is able to obtain unauthorized access to or misuse authorized access to cloud services (e.g. Google's Android Device Manager or Apple iCloud's Find my iPhone) or to an enterprise mobility management (EMM) / mobile device management (MDM) server console could use that access to track mobile devices.[1]

An adversary who is able to obtain unauthorized access to or misuse authorized access to cloud services (e.g. Google's Android Device Manager or Apple iCloud's Find my iPhone) or to an EMM console could use that access to wipe enrolled devices [1].

Adversaries may rename legitimate / system utilities to try to evade security mechanisms concerning the usage of those utilities. Security monitoring and control mechanisms may be in place for legitimate utilities adversaries are capable of abusing, including both built-in binaries and tools such as PSExec, AutoHotKey, and IronPython.[1][2][3][4] It may be possible to bypass those security mechanisms by renaming the utility prior to utilization (ex: rename rundll32.exe).[5] An alternative case occurs when a legitimate utility is copied or moved to a different directory and renamed to avoid detections based on these utilities executing from non-standard paths.[6]

Adversaries may move onto systems, possibly those on disconnected or air-gapped networks, by copying malware to removable media and taking advantage of Autorun features when the media is inserted into a system and executes. In the case of Lateral Movement, this may occur through modification of executable files stored on removable media or by copying malware and renaming it to look like a legitimate file to trick users into executing it on a separate system. In the case of Initial Access, this may occur through manual manipulation of the media, modification of systems used to initially format the media, or modification to the media's firmware itself.

Mobile devices may also be used to infect PCs with malware if connected via USB.[1] This infection may be achieved using devices (Android, iOS, etc.) and, in some instances, USB charging cables.[2][3] For example, when a smartphone is connected to a system, it may appear to be mounted similar to a USB-connected disk drive. If malware that is compatible with the connected system is on the mobile device, the malware could infect the machine (especially if Autorun features are enabled).

Adversaries may move onto devices by exploiting or copying malware to devices connected via USB. In the case of Lateral Movement, adversaries may utilize the physical connection of a device to a compromised or malicious charging station or PC to bypass application store requirements and install malicious applications directly.[1] In the case of Initial Access, adversaries may attempt to exploit the device via the connection to gain access to data stored on the device.[2] Examples of this include: * Exploiting insecure bootloaders in a Nexus 6 or 6P device over USB and gaining the ability to perform actions including intercepting phone calls, intercepting network traffic, and obtaining the device physical location.[3] * Exploiting weakly-enforced security boundaries in Android devices such as the Google Pixel 2 over USB.[4] * Products from Cellebrite and Grayshift purportedly that can exploit some iOS devices using physical access to the data port to unlock the passcode.[5]

Adversaries may move onto systems, such as those separated from the enterprise network, by copying malware to removable media which is inserted into the control systems environment. The adversary may rely on unknowing trusted third parties, such as suppliers or contractors with access privileges, to introduce the removable media. This technique enables initial access to target devices that never connect to untrusted networks, but are physically accessible.

Operators of the German nuclear power plant, Gundremmingen, discovered malware on a facility computer not connected to the internet. [1] [2] The malware included Conficker and W32.Ramnit, which were also found on eighteen removable disk drives in the facility. [3] [4] [5] [6] [7] [8] The plant has since checked for infection and cleaned up more than 1,000 computers. [9] An ESET researcher commented that internet disconnection does not guarantee system safety from infection or payload execution. [10]

Adversaries may spoof reporting messages in control system environments for evasion and to impair process control. In control systems, reporting messages contain telemetry data (e.g., I/O values) pertaining to the current state of equipment and the industrial process. Reporting messages are important for monitoring the normal operation of a system or identifying important events such as deviations from expected values.

If an adversary has the ability to Spoof Reporting Messages, they can impact the control system in many ways. The adversary can Spoof Reporting Messages that state that the process is operating normally, as a form of evasion. The adversary could also Spoof Reporting Messages to make the defenders and operators think that other errors are occurring in order to distract them from the actual source of a problem.[1]