Techniques

Adversaries may use an existing, legitimate external Web service as a means for relaying data to/from a compromised system. Popular websites, cloud services, and social media acting as a mechanism for C2 may give a significant amount of cover due to the likelihood that hosts within a network are already communicating with them prior to a compromise. Using common services, such as those offered by Google, Microsoft, or Twitter, makes it easier for adversaries to hide in expected noise.[1] Web service providers commonly use SSL/TLS encryption, giving adversaries an added level of protection.

Use of Web services may also protect back-end C2 infrastructure from discovery through malware binary analysis while also enabling operational resiliency (since this infrastructure may be dynamically changed).

Adversaries may use an existing, legitimate external Web service as a means for relaying data to/from a compromised system. Popular websites and social media, acting as a mechanism for C2, may give a significant amount of cover. This is due to the likelihood that hosts within a network are already communicating with them prior to a compromise. Using common services, such as those offered by Google or Twitter, makes it easier for adversaries to hide in expected noise. Web service providers commonly use SSL/TLS encryption, giving adversaries an added level of protection.

Use of Web services may also protect back-end C2 infrastructure from discovery through malware binary analysis, or enable operational resiliency (since this infrastructure may be dynamically changed).

Adversaries may register for web services that can be used during targeting. A variety of popular websites exist for adversaries to register for a web-based service that can be abused during later stages of the adversary lifecycle, such as during Command and Control (Web Service), Exfiltration Over Web Service, or Phishing. Using common services, such as those offered by Google, GitHub, or Twitter, makes it easier for adversaries to hide in expected noise.[1][2] By utilizing a web service, adversaries can make it difficult to physically tie back operations to them.

Adversaries may compromise access to third-party web services that can be used during targeting. A variety of popular websites exist for legitimate users to register for web-based services, such as GitHub, Twitter, Dropbox, Google, SendGrid, etc. Adversaries may try to take ownership of a legitimate user's access to a web service and use that web service as infrastructure in support of cyber operations. Such web services can be abused during later stages of the adversary lifecycle, such as during Command and Control (Web Service), Exfiltration Over Web Service, or Phishing.[1] Using common services, such as those offered by Google or Twitter, makes it easier for adversaries to hide in expected noise. By utilizing a web service, particularly when access is stolen from legitimate users, adversaries can make it difficult to physically tie back operations to them. Additionally, leveraging compromised web-based email services may allow adversaries to leverage the trust associated with legitimate domains.

Adversaries can use stolen session cookies to authenticate to web applications and services. This technique bypasses some multi-factor authentication protocols since the session is already authenticated.[1]

Authentication cookies are commonly used in web applications, including cloud-based services, after a user has authenticated to the service so credentials are not passed and re-authentication does not need to occur as frequently. Cookies are often valid for an extended period of time, even if the web application is not actively used. After the cookie is obtained through Steal Web Session Cookie or Web Cookies, the adversary may then import the cookie into a browser they control and is then able to use the site or application as the user for as long as the session cookie is active. Once logged into the site, an adversary can access sensitive information, read email, or perform actions that the victim account has permissions to perform.

There have been examples of malware targeting session cookies to bypass multi-factor authentication systems.[2]

Adversaries can use stolen session cookies to authenticate to web applications and services. This technique bypasses some multi-factor authentication protocols since the session is already authenticated.[1]

Authentication cookies are commonly used in web applications, including cloud-based services, after a user has authenticated to the service so credentials are not passed and re-authentication does not need to occur as frequently. Cookies are often valid for an extended period of time, even if the web application is not actively used. After the cookie is obtained through Steal Web Session Cookie, the adversary then imports the cookie into a browser they control and is able to use the site or application as the user for as long as the session cookie is active. Once logged into the site, an adversary can access sensitive information, read email, or perform actions that the victim account has permissions to perform.

There have been examples of malware targeting session cookies to bypass multi-factor authentication systems.[2]

Adversaries may backdoor web servers with web shells to establish persistent access to systems. A Web shell is a Web script that is placed on an openly accessible Web server to allow an adversary to access the Web server as a gateway into a network. A Web shell may provide a set of functions to execute or a command-line interface on the system that hosts the Web server.[1]

In addition to a server-side script, a Web shell may have a client interface program that is used to talk to the Web server (e.g. China Chopper Web shell client).[2]

A Web shell is a Web script that is placed on an openly accessible Web server to allow an adversary to use the Web server as a gateway into a network. A Web shell may provide a set of functions to execute or a command-line interface on the system that hosts the Web server. In addition to a server-side script, a Web shell may have a client interface program that is used to talk to the Web server (see, for example, China Chopper Web shell client). [1]

Web shells may serve as Redundant Access or as a persistence mechanism in case an adversary's primary access methods are detected and removed.

Adversaries may block access to Wi-Fi communications to prevent messages from reaching target systems and devices. Wi-Fi connections allow for communications between IT and OT systems and devices. Blocking Wi-Fi communications may also block command and reporting messages.[1]

An adversary may block Wi-Fi communications by disabling network interfaces, Service Stop, conducting an Adversary-in-the-Middle attack and dropping the network traffic, or by jamming the Wi-Fi signal.

Adversaries may search for information about Wi-Fi networks, such as network names and passwords, on compromised systems. Adversaries may use Wi-Fi information as part of Account Discovery, Remote System Discovery, and other discovery or Credential Access activity to support both ongoing and future campaigns.

Adversaries may collect various types of information about Wi-Fi networks from hosts. For example, on Windows names and passwords of all Wi-Fi networks a device has previously connected to may be available through `netsh wlan show profiles` to enumerate Wi-Fi names and then `netsh wlan show profile “Wi-Fi name” key=clear` to show a Wi-Fi network’s corresponding password.[1][2][3] Additionally, names and other details of locally reachable Wi-Fi networks can be discovered using calls to `wlanAPI.dll` Native API functions.[4]

On Linux, names and passwords of all Wi-Fi-networks a device has previously connected to may be available in files under ` /etc/NetworkManager/system-connections/`.[5] On macOS, the password of a known Wi-Fi may be identified with ` security find-generic-password -wa wifiname` (requires admin username/password).[6]

Adversaries may search for information about Wi-Fi networks, such as network names and passwords, on compromised systems. Adversaries may use Wi-Fi information as part of Discovery or Credential Access activity to support both ongoing and future campaigns.

Adversaries may gain initial access to target systems by connecting to wireless networks. They may accomplish this by exploiting open Wi-Fi networks used by target devices or by accessing secured Wi-Fi networks — requiring Valid Accounts — belonging to a target organization.[1][2] Establishing a connection to a Wi-Fi access point requires a certain level of proximity to both discover and maintain a stable network connection.

Adversaries may establish a wireless connection through various methods, such as by physically positioning themselves near a Wi-Fi network to conduct close access operations. To bypass the need for physical proximity, adversaries may attempt to remotely compromise nearby third-party systems that have both wired and wireless network connections available (i.e., dual-homed systems). These third-party compromised devices can then serve as a bridge to connect to a target’s Wi-Fi network.[2]

Once an initial wireless connection is achieved, adversaries may leverage this access for follow-on activities in the victim network or further targeting of specific devices on the network. Adversaries may perform Network Sniffing or Adversary-in-the-Middle activities for Credential Access or Discovery.

Windows systems have hidden network shares that are accessible only to administrators and provide the ability for remote file copy and other administrative functions. Example network shares include C$, ADMIN$, and IPC$.

Adversaries may use this technique in conjunction with administrator-level Valid Accounts to remotely access a networked system over server message block (SMB) [1] to interact with systems using remote procedure calls (RPCs), [2] transfer files, and run transferred binaries through remote Execution. Example execution techniques that rely on authenticated sessions over SMB/RPC are Scheduled Task/Job, Service Execution, and Windows Management Instrumentation. Adversaries can also use NTLM hashes to access administrator shares on systems with Pass the Hash and certain configuration and patch levels. [3]

The Net utility can be used to connect to Windows admin shares on remote systems using net use commands with valid credentials. [4]

Adversaries may abuse the Windows command shell for execution. The Windows command shell (cmd) is the primary command prompt on Windows systems. The Windows command prompt can be used to control almost any aspect of a system, with various permission levels required for different subsets of commands. The command prompt can be invoked remotely via Remote Services such as SSH.[1]

Batch files (ex: .bat or .cmd) also provide the shell with a list of sequential commands to run, as well as normal scripting operations such as conditionals and loops. Common uses of batch files include long or repetitive tasks, or the need to run the same set of commands on multiple systems.

Adversaries may leverage cmd to execute various commands and payloads. Common uses include cmd to execute a single command, or abusing cmd interactively with input and output forwarded over a command and control channel.

Adversaries may abuse the Windows command shell for execution. The Windows command shell (cmd) is the primary command prompt on Windows systems which is used in industrial control system environments. The Windows command prompt can be used to control almost any aspect of a system, with various permission levels required for different subsets of commands. The command prompt can be invoked remotely via Remote Services (e.g., Telnet, SSH, RDP, etc.)

Batch files (ex: .bat or .cmd) also provide the shell with a list of sequential commands to run, as well as normal scripting operations such as conditionals and loops. Common uses of batch files include long or repetitive tasks, or the need to run the same set of commands on multiple systems.

Adversaries may leverage cmd to execute various commands and payloads. Common uses include cmd to execute a single command, or abusing cmd interactively with input and output forwarded over a command and control channel.

Within industrial control system networks, adversaries may abuse the use of Windows Command Shell on overlap assets that run on Microsoft Windows operating systems (Workstations, Data Historians, Human Machine Interfaces, Application Servers, Jump Hosts, etc.).

Adversaries may acquire credentials from the Windows Credential Manager. The Credential Manager stores credentials for signing into websites, applications, and/or devices that request authentication through NTLM or Kerberos in Credential Lockers (previously known as Windows Vaults).[1][2]

The Windows Credential Manager separates website credentials from application or network credentials in two lockers. As part of Credentials from Web Browsers, Internet Explorer and Microsoft Edge website credentials are managed by the Credential Manager and are stored in the Web Credentials locker. Application and network credentials are stored in the Windows Credentials locker.

Credential Lockers store credentials in encrypted `.vcrd` files, located under `%Systemdrive%\Users\\[Username]\AppData\Local\Microsoft\\[Vault/Credentials]\`. The encryption key can be found in a file named Policy.vpol, typically located in the same folder as the credentials.[3][4]

Adversaries may list credentials managed by the Windows Credential Manager through several mechanisms. vaultcmd.exe is a native Windows executable that can be used to enumerate credentials stored in the Credential Locker through a command-line interface. Adversaries may also gather credentials by directly reading files located inside of the Credential Lockers. Windows APIs, such as CredEnumerateA, may also be absued to list credentials managed by the Credential Manager.[5][6]

Adversaries may also obtain credentials from credential backups. Credential backups and restorations may be performed by running rundll32.exe keymgr.dll KRShowKeyMgr then selecting the “Back up...” button on the “Stored User Names and Passwords” GUI.

Password recovery tools may also obtain plain text passwords from the Credential Manager.[4]

Adversaries may disable or modify the Windows host firewall to bypass controls limiting network usage. This can include disabling the Windows host firewall entirely, suppressing specific profiles (domain, private, public), or adding, deleting, and modifying firewall rules to allow or restrict traffic.[1]

Adversaries may perform these modifications through multiple mechanisms depending on the Windows operating system and access level. For example, adversaries may use command-line utilities (e.g., `netsh advfirewall` or PowerShell cmdlets like `Set-NetFirewallProfile`, `New-NetFirewallRule`), Windows Registry modifications (e.g., altering firewall states and rule configurations via registry keys), or the Windows Control Panel to modify firewall settings through the Windows Security interface.

By disabling or modifying Windows firewall services, adversaries may enable access to remote services, open ports for command and control traffic, or configure rules for further actions.

Adversaries may abuse Windows Management Instrumentation (WMI) to execute malicious commands and payloads. WMI is designed for programmers and is the infrastructure for management data and operations on Windows systems.[1] WMI is an administration feature that provides a uniform environment to access Windows system components.

The WMI service enables both local and remote access, though the latter is facilitated by Remote Services such as Distributed Component Object Model and Windows Remote Management.[1] Remote WMI over DCOM operates using port 135, whereas WMI over WinRM operates over port 5985 when using HTTP and 5986 for HTTPS.[1] [2]

An adversary can use WMI to interact with local and remote systems and use it as a means to execute various behaviors, such as gathering information for Discovery as well as Execution of commands and payloads.[2] For example, `wmic.exe` can be abused by an adversary to delete shadow copies with the command `wmic.exe Shadowcopy Delete` (i.e., Inhibit System Recovery).[3]

**Note:** `wmic.exe` is deprecated as of January of 2024, with the WMIC feature being “disabled by default” on Windows 11+. WMIC will be removed from subsequent Windows releases and replaced by PowerShell as the primary WMI interface.[4] In addition to PowerShell and tools like `wbemtool.exe`, COM APIs can also be used to programmatically interact with WMI via C++, .NET, VBScript, etc.[4]

Adversaries may establish persistence and elevate privileges by executing malicious content triggered by a Windows Management Instrumentation (WMI) event subscription. WMI can be used to install event filters, providers, consumers, and bindings that execute code when a defined event occurs. Examples of events that may be subscribed to are the wall clock time, user login, or the computer's uptime.[1]

Adversaries may use the capabilities of WMI to subscribe to an event and execute arbitrary code when that event occurs, providing persistence on a system.[2][3] Adversaries may also compile WMI scripts – using `mofcomp.exe` –into Windows Management Object (MOF) files (.mof extension) that can be used to create a malicious subscription.[4][5]

WMI subscription execution is proxied by the WMI Provider Host process (WmiPrvSe.exe) and thus may result in elevated SYSTEM privileges.

Windows Management Instrumentation (WMI) can be used to install event filters, providers, consumers, and bindings that execute code when a defined event occurs. Adversaries may use the capabilities of WMI to subscribe to an event and execute arbitrary code when that event occurs, providing persistence on a system. Adversaries may attempt to evade detection of this technique by compiling WMI scripts into Windows Management Object (MOF) files (.mof extension). [1] Examples of events that may be subscribed to are the wall clock time or the computer's uptime. [2] Several threat groups have reportedly used this technique to maintain persistence. [3]

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.).

Windows implements file and directory ACLs as Discretionary Access Control Lists (DACLs).[3] Similar to a standard ACL, DACLs identifies the accounts that are allowed or denied access to a securable object. When an attempt is made to access a securable object, the system checks the access control entries in the DACL in order. If a matching entry is found, access to the object is granted. Otherwise, access is denied.[4]

Adversaries can interact with the DACLs using built-in Windows commands, such as `icacls`, `cacls`, `takeown`, and `attrib`, which can grant adversaries higher permissions on specific files and folders. Further, PowerShell provides cmdlets that can be used to retrieve or modify file and directory DACLs. 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, or tainting/hijacking other instrumental binary/configuration files via Hijack Execution Flow.

Adversaries may use Valid Accounts to interact with remote systems using Windows Remote Management (WinRM). The adversary may then perform actions as the logged-on user.

WinRM is the name of both a Windows service and a protocol that allows a user to interact with a remote system (e.g., run an executable, modify the Registry, modify services).[1] It may be called with the `winrm` command or by any number of programs such as PowerShell.[2] WinRM can be used as a method of remotely interacting with Windows Management Instrumentation.[3]

Windows Remote Management (WinRM) is the name of both a Windows service and a protocol that allows a user to interact with a remote system (e.g., run an executable, modify the Registry, modify services). [1] It may be called with the winrm command or by any number of programs such as PowerShell. [2]

Adversaries may create or modify Windows services to repeatedly execute malicious payloads as part of persistence. When Windows boots up, it starts programs or applications called services that perform background system functions.[1] Windows service configuration information, including the file path to the service's executable or recovery programs/commands, is stored in the Windows Registry.

Adversaries may install a new service or modify an existing service to execute at startup in order to persist on a system. Service configurations can be set or modified using system utilities (such as sc.exe), by directly modifying the Registry, or by interacting directly with the Windows API.

Adversaries may also use services to install and execute malicious drivers. For example, after dropping a driver file (ex: `.sys`) to disk, the payload can be loaded and registered via Native API functions such as `CreateServiceW()` (or manually via functions such as `ZwLoadDriver()` and `ZwSetValueKey()`), by creating the required service Registry values (i.e. Modify Registry), or by using command-line utilities such as `PnPUtil.exe`.[2][3][4] Adversaries may leverage these drivers as Rootkits to hide the presence of malicious activity on a system. Adversaries may also load a signed yet vulnerable driver onto a compromised machine (known as "Bring Your Own Vulnerable Driver" (BYOVD)) as part of Exploitation for Privilege Escalation.[5][4]

Services may be created with administrator privileges but are executed under SYSTEM privileges, so an adversary may also use a service to escalate privileges. Adversaries may also directly start services through Service Execution.

To make detection analysis more challenging, malicious services may also incorporate Masquerade Task or Service (ex: using a service and/or payload name related to a legitimate OS or benign software component). Adversaries may also create ‘hidden’ services (i.e., Hide Artifacts), for example by using the `sc sdset` command to set service permissions via the Service Descriptor Definition Language (SDDL). This may hide a Windows service from the view of standard service enumeration methods such as `Get-Service`, `sc query`, and `services.exe`.[6][7]

Winlogon.exe is a Windows component responsible for actions at logon/logoff as well as the secure attention sequence (SAS) triggered by Ctrl-Alt-Delete. Registry entries in HKLM\Software\[Wow6432Node\]Microsoft\Windows NT\CurrentVersion\Winlogon\ and HKCU\Software\Microsoft\Windows NT\CurrentVersion\Winlogon\ are used to manage additional helper programs and functionalities that support Winlogon. [1]

Malicious modifications to these Registry keys may cause Winlogon to load and execute malicious DLLs and/or executables. Specifically, the following subkeys have been known to be possibly vulnerable to abuse: [1]

* Winlogon\Notify - points to notification package DLLs that handle Winlogon events * Winlogon\Userinit - points to userinit.exe, the user initialization program executed when a user logs on * Winlogon\Shell - points to explorer.exe, the system shell executed when a user logs on

Adversaries may take advantage of these features to repeatedly execute malicious code and establish Persistence.