Threat Actors Weaponizing DCOM to harvest credentials on Windows systems

Threat actors are now leveraging the often-overlooked Component Object Model (COM) and its distributed counterpart, Distributed Component Object Model (DCOM), to harvest credentials on Windows systems.

As traditional red team methods like direct access to the Local Security Authority Subsystem Service (LSASS) face heightened scrutiny from Microsoft’s enhanced defenses and advanced Endpoint Detection and Response (EDR) solutions, attackers are pivoting to more stealthy, fileless techniques.

This emerging threat, detailed in a recent technical blog, demonstrates how attackers can exploit DCOM objects to coerce NTLM authentications, enabling credential theft and lateral movement without deploying payloads or triggering common security alerts.

Exploits Underutilized COM Objects

Central to this attack vector is a newly developed tool named RemoteMonologue, built in Python using the Impacket library.

This tool automates the exploitation of specific DCOM objects, such as ServerDataCollectorSet, FileSystemImage, and UpdateSession, to coerce authentications remotely.

By modifying registry settings like the RunAs key to “Interactive User,” attackers can execute DCOM objects under the security context of logged-in users, hijacking sessions without needing their credentials.

RemoteMonologue also supports tactics like NetNTLMv1 downgrade attacks, which force systems to use less secure authentication protocols for easier credential cracking, and enables the WebClient service to facilitate HTTP-based NTLM relay attacks to services like LDAP.

The ability to capture both user and machine account credentials sometimes via simple property modifications rather than method invocation amplifies the risk, as machine accounts can be used to forge silver tickets or exploit Active Directory permissions for privilege escalation.

RemoteMonologue Tool Automates Sophisticated Attacks

According to IBM Report, this attack methodology stands out for its subtlety and effectiveness in evading detection.

By avoiding direct interaction with LSASS or payload execution, which are heavily monitored by modern security tools, threat actors minimize their footprint on target systems.

The use of UNC paths in DCOM object properties or methods, such as pointing to a malicious listener, triggers network authentication attempts that yield NTLMv1 or NTLMv2 hashes.

These can be cracked offline using publicly available rainbow tables or relayed to other services like SMB or LDAP, especially since many domain controllers still lack enforced LDAP signing or channel binding.

Additionally, the potential to downgrade authentication protocols via registry modifications like LmCompatibilityLevel further simplifies credential harvesting, posing a significant challenge to organizations not on the latest Windows versions, such as Windows Server 2025, where NTLMv1 is deprecated.

For defenders, mitigating this threat requires a multi-layered approach focused on hardening systems and enhancing monitoring.

Enabling LDAP signing and channel binding on domain controllers, enforcing SMB signing, and upgrading to the latest Windows versions to eliminate NTLMv1 support are critical steps.

Strong password policies can also deter offline cracking attempts. Detection efforts should prioritize monitoring remote access to DCOM objects, tracking modifications to key registry entries like RunAs and LmCompatibilityLevel, and scrutinizing unexpected activations of the WebClient service.

As the RemoteMonologue attack underscores, the decades-old COM technology remains a potent attack surface, urging organizations to revisit their security posture to counter these sophisticated, fileless threats before they escalate into full-scale breaches.

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