VMware Horizon 7.13 Agent Security Technical Implementation Guide

The Horizon Agent has the capability to be backward compatible with legacy clients, circa View 5.2, which do not support newer TLS connections. By default, the agent can fall back to this non-TLS mode when being accessed by a legacy client. The Horizon Agent must be configured to not support these legacy clients and enforce TLS connections as mandatory.

The Horizon Agent has the capability to run scripts on user connect, disconnect, and reconnect. While this can be useful in setting up a user environment, in certain circumstances, the running of such scripts should be delegated to native windows capabilities where possible. These settings are powerful and can serve as a potential space for a privileged attacker to persist. By default, this setting is unconfigured. Should the site require this setting, ensure it is audited and its configuration valid at all times.

The Horizon Agent has the capability to run scripts on user connect, disconnect, and reconnect. While this can be useful in setting up a user environment, in certain circumstances, the running of such scripts should be delegated to native windows capabilities where possible. These settings are powerful and can serve as a potential space for a privileged attacker to persist. By default, this setting is unconfigured. Should site require this setting, ensure it is audited and its configuration valid at all times.

The Horizon Agent has the capability to run scripts on user connect, disconnect, and reconnect. While this can be useful in setting up a user environment, in certain circumstances, the running of such scripts should be delegated to native windows capabilities where possible. These settings are powerful and can serve as a potential space for a privileged attacker to persist. By default, this setting is unconfigured. Should a site require this setting, ensure it is audited and the configuration valid at all times.

Any time the Horizon Agent establishes an outgoing TLS connection, it verifies the server certificate revocation status. By default, it verifies all intermediates but not the root. DoD policy requires full path validation, thus this default behavior needs to be changed.

Idle sessions are at increased risk of being hijacked. If a user has stepped away from their desk and is no long in positive control of their session, that session is in danger of being assumed by an attacker. Idle sessions also waste valuable datacenter resources and could potentially lead to a lack of resources for new, active users. As such, an organizationally defined idle timeout must be supplied to override the Horizon default of "never".

Data loss prevention is a primary concern for the DoD, maintaining positive control of data at all times and only allowing flows over channels that are for that explicit purpose and monitored appropriately. By default, the Blast protocol on the Horizon Agent will block clipboard "copy/paste" actions from the desktop to the client but allow actions from the client to the desktop. This configuration must be validated and maintained over time.

Data loss prevention is a primary concern for the DoD, maintaining positive control of data at all times and only allowing flows over channels that are for that explicit purpose and monitored appropriately. By default, the PCoIP protocol on the Horizon Agent will block clipboard "copy/paste" actions from the desktop to the client but allow actions from the client to the desktop. This configuration must be validated and maintained over time.

Data loss prevention is a primary concern for the DoD, maintaining positive control of data at all times and only allowing flows over channels that are for that explicit purpose and monitored appropriately. Additionally, data coming into the environment must be through allowed channels and inspected appropriately. By default, the Blast protocol on the Horizon Agent will allow file transfers through HTML Access only from the client to the desktop. This must be configured to disabled in both directions.

Data loss prevention is a primary concern for the DoD, maintaining positive control of data at all times and only allowing flows over channels that are for that explicit purpose and monitored appropriately. Additionally, data coming into the environment must be through allowed channels and inspected appropriately. By default, the Blast protocol on the Horizon Agent will allow drag and drop actions from the client to the desktop. This must be configured to disabled in both directions.

Data loss prevention is a primary concern for the DoD, maintaining positive control of data at all times and only allowing flows over channels that are for that explicit purpose and monitored appropriately. Additionally, data coming into the environment must be through allowed channels and inspected appropriately. By default, the PCoIP protocol on the Horizon Agent will allow drag and drop actions from the client to the desktop. This must be configured to disabled in both directions.

Data loss prevention is a primary concern for the DoD, maintaining positive control of data at all times and only allowing flows over channels that are for that explicit purpose and monitored appropriately. By default, the Blast protocol on the Horizon Agent will block clipboard "copy/paste" actions from the desktop to the client but allow actions from the client to the desktop. All such allowed actions must be audited for potential future forensic purposes.

Data loss prevention is a primary concern for the DoD, maintaining positive control of data at all times and only allowing flows over channels that are for that explicit purpose and monitored appropriately. By default, the PCoIP protocol on the Horizon Agent will block clipboard "copy/paste" actions from the desktop to the client but allow actions from the client to the desktop. All such allowed actions must be audited for potential future forensic purposes.

Data loss prevention is a primary concern for the DoD, maintaining positive control of data at all times and only allowing flows over channels that are for that explicit purpose and monitored appropriately. By default, the Horizon Client, Agent, and guest operating systems will coordinate to allow drives local to the client to be redirected over the Client connection and mounted in the virtual desktop. This configuration must be modified to disallow drive sharing in order to protect sensitive DoD data from being maliciously, accidentally, or casually removed from the controlled environment.

The Horizon Agent has the capability to granularly control what, if any, USB devices are allowed to be passed from the local client to the agent on the virtual desktop. By default, Horizon blocks certain device families from being redirected to the remote desktop or application. For example, HID (human interface devices) and keyboards are blocked from appearing in the guest as released BadUSB code targets USB keyboard devices. While there are legitimate reasons to pass USB devices to the desktop, these must be carefully analyzed for necessity. At a minimum, USB Mass Storage devices must never passed through, in keeping with long-standing DoD data loss prevention policies. As thumb drives are disallowed for physical PCs, so should they be for virtual desktops. This can be accomplished in many ways, including natively in the Horizon Agent.