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Confidential Box

ConfidentialBox is a sandbox setting in Sandboxie Ini. It enables additional protection for the processes and threads running in a sandbox.

[DefaultBox]
ConfidentialBox=y

The setting is disabled by default and requires a currently applicable Support Certificate.

What it protects

With ConfidentialBox=y, the driver checks access rights requested by unsandboxed host processes when creating or duplicating handles to sandboxed processes or threads. This includes read-only and query access, not only rights that could modify or control the target.

This protection is scoped to process and thread handles. It does not encrypt files, protect the mounted box root, or automatically restrict network, clipboard, GUI, IPC, and other permitted data-transfer paths. Use Box Encryption when encrypted backing storage is required.

Sandboxie retains operational exceptions for components and Windows processes needed to manage or run the sandbox. These include SbieSvc and Start, selected core or protected Windows processes, the process that is starting a target during its initialization, and an eligible SandMan or Sandboxie Control session leader. ProtectAdminOnly determines whether that session-leader exception requires administrative access.

DenyHostAccess

DenyHostAccess supplies program-specific rules for the same process/thread protection path. It can be used independently of ConfidentialBox.

[DefaultBox]
DenyHostAccess=monitor.exe,y
DenyHostAccess=audiodg.exe,n

The general syntax is:

DenyHostAccess=[host-program-or-group,]y|n
  • y denies the matching unsandboxed host program.
  • y applies the access restriction to the matching unsandboxed host program, subject to the operational exceptions described above.
  • n exempts the matching program from this particular protection check. It does not grant rights that Windows or other checks would otherwise deny.
  • With no program prefix, the value supplies the box-wide default. DenyHostAccess=y is therefore equivalent to a default deny rule.
  • Program selectors use Sandboxie's program-name matching, including wildcards, and can refer to configured process groups.

Without ConfidentialBox, DenyHostAccess is evaluated when a host process requests rights outside Sandboxie's normally permitted access subset, which differs for process and thread handles. Requests containing only rights within the applicable subset do not trigger this particular restriction.

In the object-filter path, a matching deny rule restricts the requested access mask for handle creation or duplication rather than directly rejecting the operation. If the operation succeeds, the resulting handle may have no usable access rights. Independent Windows access checks or protected-process restrictions may still cause the operation to fail.

With ConfidentialBox, the same check also covers read-only and query requests, and the default becomes deny for host programs. An explicit DenyHostAccess=program.exe,n entry can create a compatibility exception. The built-in Less Confidential Box template currently uses such an exception for audiodg.exe.

The operational exceptions described above still apply. DenyHostAccess is not a general filesystem rule and does not block the named executable from every form of interaction with the sandbox.

  • Box Encryption protects the sandbox's backing storage and can add mounted-root protection. It is independent of ConfidentialBox.
  • ProtectAdminOnly controls the session-leader exception for protected processes and for an encrypted root mounted with root protection.
  • ProtectHostImages restricts executable images loaded by certain sandboxed processes. It is a separate protection path.

SandMan configuration

The controls are under:

Sandbox Options > Security Options > Box Protection

  • Protect processes within this box from host processes writes ConfidentialBox=y when selected.
  • Allow useful Windows processes access to protected processes enables the Less Confidential Box compatibility template.
  • The host-process list and its Allow Process and Deny Process actions write DenyHostAccess entries.
  • When box root is protected require SandMan to run as Administrator in order to access the files controls ProtectAdminOnly.

The UI's host-process editor accepts program names. More advanced program-group or wildcard rules can be configured manually.

Applying changes

ConfidentialBox is recorded when each sandboxed process is initialized, so restart the affected sandboxed process tree after changing it. DenyHostAccess and the process-access part of ProtectAdminOnly are consulted during host access checks after configuration reload.

Version history

ConfidentialBox and DenyHostAccess were introduced in Sandboxie Plus 1.3.3 / Classic 5.58.3. Encrypted sandbox images were added later, in Sandboxie Plus 1.11.0 / Classic 5.66.0.