From Azure AD to Active Directory (via Azure) – An Unanticipated Attack Path

For most of 2019, I was digging into Office 365 and Azure AD and looking at features as part of the development of the new Trimarc Microsoft Cloud Security Assessment which focuses on improving customer Microsoft Office 365 and Azure AD security posture. As I went through each of them, I found one that was very interesting.

In May 2020, I presented some Microsoft Office 365 & Azure Active Directory security topics in a Trimarc Webcast called “Securing Office 365 and Azure AD: Protect Your Tenant” and included the attack path described in this article that takes advantage of a little known feature.

While Azure leverages Azure Active Directory for some things, Azure AD roles don’t directly affect Azure (or Azure RBAC) typically. This article details a known configuration (at least to those who have dug into Azure AD configuration options) where it’s possible for a Global Administrator (aka Company Administrator) in Azure Active Directory to gain control of Azure through a tenant option. This is “by design” as a “break-glass” (emergency) option that can be used to (re)gain Azure admin rights if such access is lost.
In this post I explore the danger associated with this option how it is currently configured (as of May 2020).

The key takeaway here is that if you don’t carefully protect and control Global Administrator role membership and associated accounts, you could lose positive control of systems hosted in all Azure subscriptions as well as Office 365 service data.

Most of the research around this issue was performed during August 2019 through December 2019 and Microsoft may have incorporated changes since then in functionality and/or capability.

Attack Scenario:
In this scenario, Acme has an on-premises Active Directory environment. Acme embraced Azure Infrastructure as a Service (IAAS) as an additional datacenter and deployed Domain Controllers to Azure for their on-prem AD (as their “cloud datacenter”). Acme IT locked down the DCs following hardening advice and limited Azure administration to the VMs hosting the DCs. Acme has other sensitive applications hosted on servers in Azure.

Acme signed up for Office 365 and started a pilot. All of the Active Directory and Exchange admins (and many other IT admins) are granted temporary Global Administrator (aka Global Admin or GA) rights to facilitate the pilot. So, more than should be there and not well protected.

The Global Administrator role provides full admin rights to Azure AD and ultimately all Office 365 services.
The Microsoft online document provides key information (5/26/2020):

Note that there is nothing stated here about Azure capability.

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Attack Methods for Gaining Domain Admin Rights in Active Directory

There are many ways an attacker can gain Domain Admin rights in Active Directory. This post is meant to describe some of the more popular ones in current use. The techniques described here “assume breach” where an attacker already has a foothold on an internal system and has gained domain user credentials (aka post-exploitation).

The unfortunate reality for most enterprises, is that it often does not take long from an attacker to go from domain user to domain admin. The question on defenders’ minds is “how does this happen?”.

The attack frequently starts with a spear-phishing email to one or more users enabling the attacker to get their code running on a computer inside the target network. Once the attacker has their code running inside the enterprise, the first step is performing reconnaissance to discover useful resources to escalate permissions, persist, and of course, plunder information (often the “crown jewels” of an organization).

While the overall process detail varies, the overall theme remains:

  • Malware Injection (Spear-Phish, Web Exploits, etc)
  • Reconnaissance (Internal)
  • Credential Theft
  • Exploitation & Privilege Escalation
  • Data Access & Exfiltration
  • Persistence (retaining access)

We start with the attacker having a foothold inside the enterprise, since this is often not difficult in modern networks. Furthermore, it is also typically not difficult for the attacker to escalate from having user rights on the workstation to having local administrator rights. This escalation can occur by either exploiting an unpatched privilege escalation vulnerability on the system or more frequently, finding local admin passwords in SYSVOL, such as Group Policy Preferences.

I spoke about most of these techniques when at several security conferences in 2015 (BSides, Shakacon, Black Hat, DEF CON, & DerbyCon).

I also covered some of these issues in the post “The Most Common Active Directory Security Issues and What You Can Do to Fix Them“.

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The Most Common Active Directory Security Issues and What You Can Do to Fix Them

The past couple of years of meeting with customers is enlightening since every environment, though unique, often has the same issues. These issues often boil down to legacy management of the enterprise Microsoft platform going back a decade or more.

I spoke about Active Directory attack and defense at several security conferences this year including BSides, Shakacon, Black Hat, DEF CON, and DerbyCon. These talks include information about how to best protect the Active Directory enterprise from the latest, and most successful, attack vectors.

While the threats have changed over the past decade, the way systems and networks are managed often have not. We continue with the same operations and support paradigm despite the fact that internal systems are compromised regularly. We must embrace the new reality of “Assume Breach.”

Assume breach means that we must assume that an attacker has control of a computer on the internal network and can access the same resources the users who have recently logged on to that computer has access to.
Note that when I describe risks and mitigations of Active Directory,this includes overall enterprise configuration.

Here are some of the biggest AD security issues (as I see them). This list is not complete, but reflects common enterprise issues.
I continue to find many of these issues when I perform Active Directory Security Assessments for organizations.

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BSides Dublin – The Current State of Microsoft Identity Security: Common Security Issues and Misconfigurations – Sean Metcalf

We have an Identity problem and not the kind you think of when you look in the mirror. Attacks have shifted from the perimeter to the endpoints and now attackers have their sights on identity. This talk explores the issues with Identity security specifically the two most popular identity systems, Active Directory & Azure AD (“Entra ID” for those who read Microsoft’s press releases). These Identity security issues lead to compromise of systems that leverage the identity system for authentication/authorization.

Click here to read more.

DEFCON 2017: Transcript – Hacking the Cloud

Let’s look at recon in a cloud-type environment. You have a customer. They’ve hired you to come in and pen test, red team their environment, and they said, “We want to add cloud to the scope.” What does that mean? How do we identify what sort of cloud services they have?

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Detecting the Elusive: Active Directory Threat Hunting

This is “Detecting the Elusive: Active Directory Threat Hunting”, and I am Sean Metcalf. I’m the founder of Trimarc, a Security Company, a Microsoft-Certified Master (MCM) in Active Directory. There’s about 100 in the world. I’m also a Microsoft MVP. I’ve spoken about Active Directory attack and defense at a number of conferences. I’m a security consultant and researcher, and as we just found out, I run where I post a lot of interesting security information about the Microsoft platform. So what are we going to talk about?

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Detecting Kerberoasting Activity

Kerberoasting can be an effective method for extracting service account credentials from Active Directory as a regular user without sending any packets to the target system. This attack is effective since people tend to create poor passwords. The reason why this attack is successful is that most service account passwords are the same length as the domain password minimum (often 10 or 12 characters long) meaning that even brute force cracking doesn’t likely take longer than the password maximum password age (expiration).

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Detecting Password Spraying with Security Event Auditing

A common method attackers leverage as well as many penetration testers and Red Teamers is called “password spraying”. Password spraying is interesting because it’s automated password guessing. This automated password guessing against all users typically avoids account lockout since the logon attempts with a specific password are performed against against every user and not one specific one which is what account lockout was designed to defeat. The attacker starts with a list list of passwords they’re going to try which starts with the most likely passwords (“Fall2017”, “Winter2018”, etc).

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Hardening Azure AD in the Face of Emerging Threats

In September of 2021, Trimarc Founder & CTO Sean Metcalf presented at Quest’s The Experts Conference.

“This presentation covers some attacks that involve Microsoft cloud on-prem components as well as those against the Microsoft cloud directly. After discussing attacks and specific defenses, I will wrap up with some key recommendations.

Note: There will be some duplication among recommendations. That’s on purpose – if I mention something more than once, that means it’s really important!”

To view the full slide deck, click here. Enjoy!

Slides Posted for Black Hat USA 2019 Talk: Attacking & Defending the Microsoft Cloud

Attacking and Defending the Microsoft Cloud (Office 365 & Azure AD)
Sean Metcalf (Trimarc) & Mark Morowczynski (Principal Program Manager, Microsoft)

The allure of the “Cloud” is indisputable. Organizations are moving into the cloud at a rapid pace. Even companies that have said no to the Cloud in the past have started migrating services and resources. The Cloud is a new paradigm and the rapid update pace makes it difficult to keep up, especially when it comes to security.

This presentation focuses on the Microsoft Cloud (Office 365 & Azure AD) and explores the most common attacks against the Cloud and describes effective defenses and mitigation. While the content is focused on the Microsoft Cloud, some of the attack and defense topics are applicable to other cloud providers and are noted where applicable.

Key items covered:
Attacks against the Cloud
Account compromise and token theft
Methods to detect attack activity
Cloud identity firewall
Securing cloud infrastructure against attacks
Secure cloud administration

Slides (PDF)