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Introduction:
In the world of cybersecurity, offensive security testers and threat actors constantly seek unconventional methods to bypass security controls. A recent demonstration reveals that Microsoft Excel, a ubiquitous business application, can be weaponized to perform Lightweight Directory Access Protocol (LDAP) queries and extract sensitive Active Directory information, often flying under the radar of traditional security monitoring.
Learning Objectives:
- Understand the mechanism behind Excel’s data import feature and its ability to execute LDAP queries.
- Learn how to construct and execute a basic LDAP query directly from Microsoft Excel.
- Identify the potential security implications of this technique for corporate environments and learn mitigation strategies.
You Should Know:
1. Initiating the Data Connection in Excel
The first step involves accessing Excel’s powerful “Get Data” feature, which is designed for legitimate data connectivity but can be repurposed for reconnaissance.
Step-by-Step Guide:
Navigate to the `Data` tab in the Excel ribbon. Click on Get Data, hover over From Other Sources, and select From Blank Query. This action opens the Power Query Editor window. Next, in the formula bar, you will input the specific connection string to interface with your domain’s LDAP service. This method leverages Excel’s built-in data connectors, which are often trusted and allowed even in restricted environments, making it a potent tool for initial discovery.
2. Crafting the Core LDAP Connection String
The connection string is the heart of this technique, defining the target and the parameters of the directory query.
Verified Command/Snippet:
let
Source = ActiveDirectory.Domains("ldap://your-domain-controller.com")
in
Source
Step-by-Step Guide:
Replace `”your-domain-controller.com”` with the fully qualified domain name (FQDN) of your target domain controller. This M (Power Query) formula uses the `ActiveDirectory.Domains` function to initiate a connection. Upon clicking Invoke, you may be prompted for authentication credentials. In a penetration testing scenario, this could use captured credentials or leverage the current user’s context if Excel is run on a domain-joined machine.
3. Navigating and Expanding the Domain Data
Once connected, you must navigate the hierarchical data structure returned by the LDAP query to access useful information.
Verified Command/Snippet:
After invoking the initial connection, you will see a table. Click on the cell link under the `Domains` column for your target domain. This will generate a new step, such as Navigation. You then need to expand the data columns related to users, groups, or computers by clicking the double-arrow icon in the column header.
4. Querying Active Directory Users
Extracting a list of domain users is a primary objective for reconnaissance, helping to identify targets for further attacks.
Verified Command/Snippet (Advanced Query):
let
Source = ActiveDirectory.Domains("ldap://dc.corp.com"),
"corp.com" = Source{[Domain="corp.com"]}[bash],
Users = "corp.com"[bash]
in
Users
Step-by-Step Guide:
This refined query directly drills down into the `”corp.com”` domain and extracts the `Users` table. The `let…in` structure defines the data transformation steps. The `Source{[Domain=”corp.com”]}
` line filters the source data for a specific domain, and `"corp.com"[bash]` selects the Users entity. Executing this will present a table of users with attributes like SAM Account Name, Display Name, and Email.
<h2 style="color: yellow;">5. Filtering for High-Value Targets like Domain Admins</h2>
Merely listing users is noisy; a precise operator will filter for privileged accounts to maximize impact.
<h2 style="color: yellow;">Verified Command/Snippet:</h2>
Within the Power Query Editor, use the filter dropdown on the `MemberOf` column (or a similar group membership column). Search for and select groups like <code>"Domain Admins"</code>, <code>"Enterprise Admins"</code>, or <code>"Schema Admins"</code>. This will apply a filter step to your query, automatically generating the underlying M code to show only users who are members of that critical group.
<h2 style="color: yellow;">6. Extracting Computer and Server Objects</h2>
Network enumeration is critical for understanding the attack surface and identifying potential lateral movement paths.
<h2 style="color: yellow;">Verified Command/Snippet:</h2>
Modify your query to select the `Computers` entity instead of <code>Users</code>.
[bash]
let
Source = ActiveDirectory.Domains("ldap://dc.corp.com"),
"corp.com" = Source{[Domain="corp.com"]}[bash],
Computers = "corp.com"[bash]
in
Computers
Step-by-Step Guide:
This query follows the same pattern as the user query but targets computer objects. The resulting data can include the computer name, operating system, and last logon timestamp. This information is invaluable for mapping the network and identifying outdated or vulnerable systems that can be exploited.
7. Advanced Query: Using a Custom LDAP Filter
For maximum control and stealth, you can implement a raw LDAP filter directly within the Power Query.
Verified Command/Snippet:
let
Source = Directory.Search("ldap://dc.corp.com", "(&(objectCategory=person)(objectClass=user)(description=admin))")
in
Source
Step-by-Step Guide:
This method uses the more powerful `Directory.Search` function. The second parameter is a standard LDAP filter string. This example, "(&(objectCategory=person)(objectClass=user)(description=admin))", searches for user objects where the description field contains the word “admin”. You can replace this filter with any valid LDAP query, such as finding accounts with password never expires ((userAccountControl:1.2.840.113556.1.4.803:=65536)) or service principal names (SPNs) for Kerberoasting.
What Undercode Say:
- Living Off the Land, Application Edition. This technique is a classic example of a “Living Off the Land” (LotL) strategy, but applied to an application layer. It abuses a legitimate, trusted feature of Microsoft Excel for a potentially malicious purpose, making detection by signature-based security tools significantly more challenging.
- The Perimeter is an Illusion. This method demonstrates that network-level restrictions are insufficient. If a user can run Excel and reach a domain controller on port 389 (LDAP), they can potentially exfiltrate the entire corporate directory structure without downloading a single hacking tool, bypassing application whitelisting that would block utilities like PowerShell Empire or BloodHound’s SharpHound.
The true danger lies in the technique’s elegance and opacity. It requires no external binaries, leaves a minimal forensic footprint primarily within Excel’s application logs, and operates within the context of a perfectly normal business activity. Defenders can no longer assume that common office software is benign; the very tools that run the business can be used to attack it. Monitoring for unusual LDAP query volumes originating from non-standard sources like workstations running Excel becomes a new necessity.
Prediction:
The weaponization of ubiquitous business applications like Excel, Word, and Power BI for offensive security operations will become a dominant trend in the next 12-18 months. As EDR (Endpoint Detection and Response) solutions become more adept at catching traditional malware and scripts, threat actors will pivot to “application-level living off the land.” We predict a rise in sophisticated malware that does not deploy payloads but instead manipulates trusted applications through macros, add-ins, or data connections to perform reconnaissance, credential theft, and even lateral movement, effectively hiding in plain sight and forcing a fundamental rethinking of application control and user behavior analytics.
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IT/Security Reporter URL:
Reported By: Ivancabrerafresno Did – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
