1. Introduction: The Convenience Trap
Active Directory (AD) is designed for collaboration. By default, it acts like a global office directory. However, this convenience often leads to an information disclosure vulnerability. Even a low-privileged user can query a massive amount of data about every other user, group, and machine in the domain.
In this article, we explore how an attacker uses simple LDAP queries to extract sensitive information and how a Blue Teamer can surgically shut those leaks down using dsacls.
2. The Lab Setup
To follow along, the lab environment consists of two virtual machines on the same NAT network:
Target
- Windows Server 2019
- Domain Controller:
cybercommando.org
Attacker
- Kali Linux
Scenario
The attacker has already gained an initial foothold and possesses credentials of a standard domain user:
Username: prabhu
3. What is ldapsearch?
ldapsearch is a command-line utility used to query LDAP directories. While Windows administrators often rely on PowerShell and GUI tools, ldapsearch is the Swiss Army Knife for attackers and Linux-based administrators.
It allows you to:
- Bind (authenticate) to a Domain Controller
- Perform granular searches using LDAP filters
- Retrieve raw directory attributes
4. The Attacker's Reconnaissance
Once inside the network, the attacker does not need exploits. They only need to ask Active Directory the right questions.
The Global User Search
The attacker begins by listing all users and inspecting metadata fields for human mistakes.
ldapsearch -h "URL" -x -D "user@domain_name" -W -b "Domain_Name" "(objectClass=user)" description
Explanation
-
-x: Simple authentication -
-D: Bind DN (compromised user) -
-b: Base DN (search root) -
description: Attribute being queried
The Leak
The attacker discovers a user object where an administrator mentioned important details in the description field.
Because Authenticated Users have read access by default, this sensitive information is exposed to any logged-in domain user.
Impact
With this leaked password, an attacker can:
- Perform password spraying
- Identify accounts still using default credentials
- Escalate privileges silently
5. Blue Team Defense: Surgery with dsacls
Deleting the description value is only a temporary fix. The real solution is controlling who can read sensitive attributes.
Goal
- Admins can read the description
- Standard users cannot
The dsacls Command
Run the following on the Domain Controller:
dsacls "CN=manoj,CN=Users,DC=cybercommando,DC=org" /D "Authenticated Users":RP;description
Breakdown
-
CN=manoj,...: Target user object -
/D: Explicit deny -
Authenticated Users: Group being restricted -
RP;description: Deny Read Property for the description attribute only
This command can be adapted to protect multiple users or entire OUs.
6. Verification
Back on the Kali machine, rerun the same ldapsearch command.
Result
- The user object is returned
- The
descriptionattribute of User: Manoj is missing
Why This Works
The Domain Controller evaluates the ACL, detects the explicit deny rule, and redacts the sensitive attribute before responding.
Conclusion: Privacy Is a Permission
Active Directory security is not only about strong passwords; it is about visibility control.
Understanding how attackers view AD through LDAP allows Blue Teamers to:
- Identify silent data leaks
- Enforce the principle of least privilege
- Harden environments without breaking functionality
Rule of thumb:
If a standard user does not need to see an attribute to do their job, they should not be able to see it at all.
Top comments (1)
Thanks so much for sharing this knowledge and helping the community level up!