AllSigned Execution Policy

What AllSigned Means in Practice

AllSigned is not just a label for “signed scripts”, it changes the trust model for PowerShell execution. The policy assumes that code should be approved through a trusted signer before it runs, so the security question becomes whether the signature is valid, trusted, and still attached to the exact file being executed.

How AllSigned Changes Script Execution

With AllSigned enabled, PowerShell checks script and configuration files before execution and blocks content that lacks a valid trusted signature. That makes the policy effective as a gate on administrative automation, but it also means any legitimate workflow that generates or edits scripts must account for signing as part of release or change management.

The practical implication is that the policy controls trust in the code itself, not the intent of the person launching it. A script can be well written and still fail to run if it is unsigned, signed by an untrusted issuer, or altered after signing.

Common Failure Modes and Operational Trade-offs

AllSigned helps reduce casual script tampering, but it does not remove the need to inspect what a trusted signer is allowed to approve. If signing practices are weak, the policy can create a false sense of safety because malicious or inappropriate code may still run when it carries a valid signature.

It also introduces friction into environments that rely on frequent script changes, emergency fixes, or locally authored administration tools. Teams usually need a clear signing process, trusted certificate distribution, and a way to distinguish production-approved scripts from ad hoc files used during troubleshooting.

Where AllSigned Fits in PowerShell Security

AllSigned works best as one control in a broader PowerShell hardening strategy rather than a stand-alone safeguard. It is typically paired with script logging, constrained administrative paths, and controls that reduce abuse of PowerShell as an execution and post-exploitation tool. A practical overview of those relationships is covered in the PowerShell Security Guide.

Because signatures protect integrity only if the signing process and trust store are sound, organisations should align the policy with configuration management, code signing governance, and auditability. Guidance on baseline security controls is also reflected in NIST SP 800-53 Rev 5 Security and Privacy Controls, especially where integrity, configuration, and logging controls intersect.

Risk and Threat Considerations

AllSigned reduces script tampering risk, but it is only as strong as the trust placed in signers, certificates, and signing workflows. If an attacker can abuse a trusted signing path, replace a signed file before execution, or rely on a weak trust store, the policy can be bypassed in ways that still look legitimate to PowerShell.

Failure mechanism: The policy fails when the organisation trusts the wrong signer, cannot verify the origin of signed content, or allows signed malicious code to enter the execution path.

Impact: An attacker can preserve execution of harmful scripts, frustrate integrity checks, and use apparently trusted PowerShell content for persistence, automation abuse, or lateral movement.

Practitioner Guidance

Why practitioners should care: AllSigned is most useful when it is treated as part of a governed code-signing process, not as a cosmetic hardening setting. The control only delivers real value when trusted signers are tightly managed and the signing workflow is reviewed as carefully as the scripts it protects.

What to watch for: Pay special attention to unsigned admin scripts, unexpected certificate trust changes, and teams that bypass signing during urgent fixes. Those are the places where the control is most likely to be weakened in practice.

Practitioner takeaway: Use AllSigned to enforce trust, but validate the signing authority and the release process with the same discipline you apply to the code itself.

Related resources from NHI Mgmt Group

• Execution Policy
• Execution (MITRE ATT&CK Tactic)
• How should security teams close the gap between IAM policy and actual execution?
• What is the difference between kernel caching and full policy execution in user space?