Minimizing Risk: The Dangers of Neglected Active Directory Service Accounts

Active Directory (AD) service accounts often go unnoticed within organizations, existing in the background after their original purposes have been forgotten. These orphaned service accounts, which are typically created for legacy applications, scheduled tasks, automation scripts, or test environments, frequently remain active with non-expiring or stale passwords, presenting significant security risks.

Routine security oversight often neglects these service accounts. Security teams, burdened by daily responsibilities and ongoing technical debt, tend to overlook service accounts that lack direct links to individual users, allowing them to fade from attention. This obscurity makes them attractive targets for attackers seeking covert access to networks. If left unchecked, forgotten service accounts can act as silent pathways for attacks and lateral movements across enterprise ecosystems. This discussion will delve into the dangers associated with these overlooked AD service accounts and present strategies to mitigate related risks.

Visibility and Inventory of Forgotten Accounts

As a fundamental principle in cybersecurity suggests, visibility is crucial for protection. This principle is especially pertinent when it comes to AD service accounts. Gaining visibility is the initial step toward securing these accounts. However, orphaned or unmonitored accounts typically operate discreetly and evade detection. Forgotten service accounts have been key factors in several high-profile breaches in recent years. For instance, during the 2020 SolarWinds attack, compromised service accounts played a significant role, enabling threat actors to navigate targeted environments and access sensitive systems.

Once attackers establish a foothold through phishing or social engineering, they usually seek out service accounts to exploit, utilizing them to escalate privileges and maneuver laterally within the network. Fortunately, administrators can employ various techniques to identify and reveal forgotten or unmonitored AD service accounts, including:

• Querying AD for service principal name (SPN)-enabled accounts, commonly used by services for authentication with other systems.
• Filtering for accounts with non-expiring passwords or those that haven’t logged in for extended periods.
• Scanning scheduled tasks and scripts for hard-coded or embedded credentials linked to inactive accounts.
• Reviewing group membership anomalies that may indicate service accounts with elevated privileges.
• Conducting a thorough audit of Active Directory.

Real-World Example: Botnet Exploitation of Forgotten Accounts

In early 2024, security researchers uncovered a botnet of over 130,000 devices targeting Microsoft 365 service accounts in a large-scale password-spraying campaign. The attackers circumvented multi-factor authentication (MFA) by exploiting basic authentication—an outdated authentication method still enabled in many environments. Because these attacks did not trigger typical security alerts, numerous organizations remained oblivious to their compromised status. Such incidents underscore the critical need for securing service accounts and discontinuing legacy authentication methods.

Privilege Creep and Silent Escalation

Service accounts that were initially assigned minimal permissions can evolve into dangerous threats over time through a process known as privilege creep. This occurs when accounts accumulate permissions due to system upgrades, role shifts, or nested group memberships. An account that begins as a low-risk utility can transform into a high-impact threat, capable of accessing critical systems without detection.

To mitigate this risk, security teams should regularly review service account roles and permissions. If access is not actively managed, even well-intentioned configurations may drift into perilous territory.

Best Practices for Securing AD Service Accounts

Managing AD service accounts effectively necessitates a strategic approach, as these accounts represent high-value targets that require meticulous handling. Important best practices for maintaining strong security around AD service accounts include:

Enforce Least Privilege

Assign only the necessary permissions for the functionality of each account. Refrain from placing service accounts in broad or powerful groups, such as Domain Administrators.

Utilize Managed Service Accounts

Managed service accounts (MSAs) and group managed service accounts (gMSAs) offer automatic password rotation and cannot be used for interactive logins, enhancing security and ease of maintenance compared to traditional user accounts.

Conduct Regular Audits

Employ built-in AD auditing or third-party tools to monitor account usage, logins, and permission modifications to identify any signs of misuse or misconfiguration.

Implement Strong Password Policies

Establish long, complex passphrases as the standard, avoiding reused or hard-coded credentials. Regular password rotations or automated management are essential.

Limit Account Usage

Prohibit interactive logins for service accounts. Assign unique accounts to each service or application, containing potential compromise impacts.

Disable Unused Accounts

Immediately disable any account that is no longer in use. Periodic queries can help identify stale or inactive accounts.

Separate Duties

Create distinct service accounts for varied functions such as application services, database access, and network tasks. This segregation minimizes the impact radius of any individual compromise.

Enforce MFA Where Necessary

While service accounts should ideally not support interactive logins, some situations may warrant exceptions. For these cases, enabling MFA can bolster security.

Utilize Dedicated Organizational Units

Grouping service accounts in specific organizational units (OUs) facilitates policy enforcement and auditing. This organization simplifies anomaly detection and consistency maintenance.

Review Dependencies and Access Regularly

As environments continue to evolve, revisit each service account’s purpose and whether it maintains the necessary access level. Adjust or retire accounts as appropriate.

Automation and Tools to Enhance AD Service Account Security

Utilizing tools like Specops Password Auditor allows for read-only scans of Active Directory, identifying weak passwords, unused accounts, and other vulnerabilities, all without modifying any AD configurations. With built-in reporting and alerts, security teams can proactively tackle AD service account risks rather than waiting for a breach. Streamlining password management, policy enforcement, and auditing through automation not only enhances security but also reduces administrative burdens.

Recognizing vulnerabilities is one aspect; prevention is equally critical. Manually implementing the best practices outlined can be an extensive task. Fortunately, solutions such as Specops Password Policy can automate numerous processes, ensuring that best practices are consistently applied across your Active Directory environment.