DCOM Weaponization by Threat Actors to Steal Windows Credentials

As Microsoft strengthens its defenses against traditional credential theft tools like Mimikatz and enhances Endpoint Detection and Response (EDR) solutions, threat actors are shifting towards more covert attack vectors.

Among these, the exploitation of legacy Windows technologies specifically the Distributed Component Object Model (DCOM) has gained prominence as an effective method for credential harvesting and lateral movement within enterprise networks.

Understanding DCOM Abuse for Credential Theft

DCOM, an extension of the Component Object Model (COM), allows software components to communicate over a network, enabling a process on one machine to invoke operations on another.

Historically underutilized by attackers, DCOM’s complexity has left much of its attack surface underexplored and, consequently, susceptible to abuse.

Attackers have discovered the ability to coerce remote NTLM authentication requests via DCOM objects, thereby capturing hashed credentials without deploying traditional payloads or directly targeting sensitive processes like LSASS.

This is primarily enabled through manipulating the “RunAs” registry value in COM AppIDs, particularly when set to “Interactive User.”

Such manipulation allows attackers to instantiate DCOM objects under the context of the currently logged-in user, even without knowledge of their credentials.

With sufficient privileges, an attacker can take ownership of AppID registry entries, adjust permissions, and set the RunAs value to “Interactive User,” effectively hijacking another user’s session.

Authentication Coercion

According to IBM Report, by focusing on fileless attack vectors, adversaries can reduce their detection footprint.

The technique involves coercing a DCOM object to authenticate to an attacker-controlled server via a crafted UNC path triggered by setting specific properties or invoking methods within susceptible DCOM objects.

Notable DCOM classes such as ServerDataCollectorSet, FileSystemImage, and UpdateSession present particularly attractive targets.

For example, manipulating the “CabFilename” property of ServerDataCollectorSet to point to a malicious UNC path can prompt the Windows authentication mechanism to leak NTLM credentials to the attacker’s listener.

Further sophistication is achieved through NTLM downgrade attacks that force the system to use less secure authentication protocols (NTLMv1), making captured hashes easier to crack offline.

Attackers can modify the registry value LmCompatibilityLevel to facilitate this downgrade, provided they have administrative privileges.

The attack methodology has been encapsulated in tools such as RemoteMonologue, which leverages the Impacket framework to automate DCOM-based authentication coercion attacks across target systems.

The tool supports credential harvesting via multiple DCOM objects, NTLMv1 downgrades, and credential spraying, substantially lowering the operational barrier for threat actors.

Mitigating DCOM-based credential theft requires a multifaceted approach. Organizations are advised to:

• Enforce LDAP signing and channel binding, a default in Windows Server 2025, to counter LDAP relay attacks.
• Upgrade systems to the latest Windows versions, where NTLMv1 has been deprecated, minimizing downgrade risks.
• Mandate SMB signing to thwart SMB relay attacks.
• Monitor for unauthorized modifications to registry settings like RunAs and LmCompatibilityLevel, and track anomalous remote DCOM object instantiations and suspicious WebClient service activity.
• Strengthen password policies to hinder offline hash cracking attempts.

The weaponization of DCOM by sophisticated threat actors represents a significant evolution in Windows credential theft and lateral movement tactics.

By exploiting the complex and under-monitored internals of DCOM, attackers can execute stealthy, fileless attacks that circumvent many conventional security controls.

As the attack surface shifts, defenders must adapt their monitoring, hardening, and incident response strategies to address these advanced methods, thereby reducing the risk and impact of credential compromise in Windows environments.

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