Are Forgotten AD Service Accounts Leaving You at Risk?

For many organizations, Active Directory (AD) service accounts are quiet afterthoughts, persisting in the background long after their original purpose has been forgotten. To make matters worse, these orphaned service accounts (created for legacy applications, scheduled tasks, automation scripts, or test environments) are often left active with non-expiring or stale passwords.

It's no surprise that AD service accounts often evade routine security oversight. Security teams, overwhelmed by daily demands and lingering technical debt, often overlook service accounts (unlinked to individual users and rarely scrutinized) allowing them to quietly fade into the background. However, this obscurity makes them prime targets for attackers seeking stealthy ways into the network. And left unchecked, forgotten service accounts can serve as silent gateways for attack paths and lateral movement across enterprise environments. In this article, we'll examine the risks that forgotten AD service accounts pose and how you can reduce your exposure.

Uncover and inventory the forgotten

As the old cybersecurity adage goes, you can't protect what you can't see. This holds especially true for AD service accounts. Gaining visibility is the first step to securing them, but orphaned or unmonitored service accounts often operate silently in the background, escaping notice and oversight. These forgotten service accounts are especially problematic, as they've played a central role in some of the most damaging breaches in recent years. In the case of the 2020 SolarWinds attack, compromised service accounts were instrumental in helping threat actors navigate targeted environments and access sensitive systems.

Once attackers gain a foothold through phishing or social engineering, their next move typically involves hunting for service accounts to exploit and using them to elevate privileges and move laterally through the network. Fortunately, administrators have a variety of techniques available to identify and uncover forgotten or unmonitored AD service accounts:

• Query AD for service principal name (SPN)-enabled accounts, which are typically used by services to authenticate with other systems.
• Filter for accounts with non-expiring passwords, or those that haven't logged in for an extended period.
• Scan scheduled tasks and scripts for hard-coded or embedded credentials that reference unused accounts.
• Review group membership anomalies, where service accounts may have inherited elevated privileges over time.
• Audit your Active Directory. You can run a read-only scan today with Specops' free AD auditing tool: Specops Password Auditor

A real-world example: Botnet exploits forgotten accounts

In early 2024, security researchers discovered a botnet of over 130,000 devices targeting Microsoft 365 service accounts in a massive password-spraying campaign. The attackers bypassed multi-factor authentication (MFA) by abusing basic authentication, an outdated authentication scheme still enabled in many environments. Because these attacks didn't trigger typical security alerts, many organizations were unaware they were compromised. This example is just one of many that highlight the importance of securing service accounts and eliminating legacy authentication mechanisms.

Privilege creep leads to silent escalation

Even service accounts that were initially created with minimal permissions can become dangerous over time. This scenario, known as privilege creep, occurs when accounts accumulate permissions due to system upgrades, role changes, or nested group memberships. What starts as a low-risk utility account can quietly evolve into a high-impact threat, capable of accessing critical systems without anyone realizing it.

Security teams should therefore review service account roles and permissions on a regular basis; if access isn't actively managed, even well-intentioned configurations can drift into risky territory.

Key practices for securing AD service accounts

Effective AD service account management requires a deliberate, disciplined approach, as these logins are high-value targets that require proper handling. Here are some best practices that form the backbone of a strong AD service account security strategy:

Enforce least privilege

Grant only the permissions absolutely necessary for each account to function. Avoid placing service accounts in broad or powerful groups like Domain Admins.

Use managed service accounts and group managed service accounts

Managed service accounts (MSAs) and group managed service accounts (gMSAs) provide automatic password rotation and cannot be used for interactive logins—this makes them safer than traditional user accounts and easier to maintain securely.

Audit regularly

Use built-in AD auditing or third-party tools to track account usage, logins, and permission changes. Watch for signs of misuse or misconfiguration.

Enforce strong password policies

Long, complex passphrases should be the standard. Avoid reused or hard-coded credentials. Passwords should be rotated regularly or managed through automated tooling.

Restrict usage

Service accounts should not allow interactive logins. Assign a unique account to each service or application to contain any potential compromise.

Actively disable unused accounts

If an account is no longer in use, it should be disabled immediately. Periodic PowerShell queries can help identify stale or inactive accounts.

Separate roles

Create distinct service accounts for different functions like application services, database access, network tasks. This compartmentalization reduces the impact radius of any one compromise.

Apply MFA where necessary

Although service accounts should not support interactive logins, some instances may require exceptions. For these edge cases, enable MFA to increase security.

Use dedicated organizational units

Grouping service accounts in specific organizational units (OUs) simplifies policy enforcement and auditing. It also makes it easier to spot anomalies and maintain consistency.

Review dependencies and access

As environments evolve, revisit what each service account is used for and whether it still needs the same level of access. Adjust or retire accounts accordingly.

Automation and tools streamline AD service account security

Specops Password Auditor performs read-only scans of Active Directory to identify weak passwords, unused accounts, and other vulnerabilities, all without changing any AD settings. With built-in reports and alerts, security teams can proactively address AD service account risks instead of waiting for a breach to happen. Automating password management, policy enforcement, and auditing both strengthens security and reduces administrative overhead. Download for free.

Finding issues is one thing, but we also need to focus on prevention. Implementing the other best practices listed in this article manually is no small feat. Fortunately, tools like Specops Password Policy can help automate many of these processes, enforcing these best practices in a manageable and scalable way across your entire Active Directory environment. Book a Specops Password Policy demo today.

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