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Introduction:
Internet Information Services (IIS) User Access Logging (UAL) is a goldmine of forensic data often overlooked in favor of traditional IIS logs. For threat hunters, understanding how to parse and analyze UAL records can reveal clandestine attacker activity, from initial compromise to lateral movement. This article decodes the structure of UAL databases and provides the technical commands to extract critical security insights.
Learning Objectives:
- Understand the location, structure, and security value of the IIS UAL database.
- Master command-line techniques for parsing UAL data without graphical interfaces.
- Learn to identify suspicious patterns and IOCs within UAL records for proactive threat hunting.
You Should Know:
1. Locating the IIS UAL Database
The UAL data is stored in a series of ETW-based databases, not plain text files. Its default location is C:\Windows\System32\LogFiles\SQS\<SID>, where `
Verified Command:
Get-ChildItem -Path "C:\Windows\System32\LogFiles\SQS\" -Recurse -Filter ".mdb"
Step-by-step guide:
This PowerShell command recursively searches all subdirectories within the SQS folder for files with the `.mdb` (Microsoft Database) extension. Each `.mdb` file corresponds to a UAL database for a specific server role (e.g., Web, FTP). Identifying these files is the first step in acquiring the raw data for analysis. Run this from an elevated PowerShell session to ensure you have the necessary permissions to access the System32 directory.
2. Using SQL Queries to Extract UAL Data
The UAL databases are structured and can be queried using SQL, provided you have the right ODBC driver. The key tables are `UAL_HTTP_CMBS` and UAL_HTTP_UR.
Verified Command:
SELECT [bash], [bash], [bash], [bash], [bash], [bash], [bash], [bash] FROM [bash];
Step-by-step guide:
This SQL command selects the most critical fields from the primary UAL table for HTTP communications. `UserName` is particularly valuable as it can reveal the account used in the attack, while `UrlStem` shows the accessed resource. To execute this, use a tool like `sqlcmd` or a graphical database browser that supports the Microsoft Access Database Engine. Connect to the `.mdb` file and run this query to dump the foundational log data.
3. Parsing UAL with PowerShell and COM Objects
For automated parsing directly in PowerShell, you can leverage the Microsoft Access Database Engine COM object to interact with the database programmatically.
Verified Command:
$conn = New-Object -ComObject "ADODB.Connection"
$rs = New-Object -ComObject "ADODB.Recordset"
$conn.Open("Provider=Microsoft.ACE.OLEDB.12.0; Data Source=C:\Path\To\Your\SQSMAP.mdb")
$rs.Open("SELECT FROM UAL_HTTP_CMBS", $conn)
while (-not $rs.EOF) { $rs.Fields.Item("UserName").Value; $rs.MoveNext() }
$rs.Close(); $conn.Close()
Step-by-step guide:
This script creates a database connection and recordset object. It opens a connection to a specific UAL database file and executes a query to select all records from the `UAL_HTTP_CMBS` table. The `while` loop iterates through each record, printing the `UserName` field as an example. This method is powerful for scripting bulk data extraction and integration into other security tools.
4. Hunting for Anomalous User Agents
Attackers often use distinctive or default User-Agent strings in their tools. Querying for unique or non-standard User-Agents can help identify automated attacks or scanning tools.
Verified Command:
SELECT DISTINCT [bash], COUNT() as RequestCount FROM [bash] GROUP BY [bash] ORDER BY RequestCount DESC;
Step-by-step guide:
This SQL query groups all HTTP requests by their `UserAgent` string and counts how many times each one appears. Sorting by `RequestCount` in descending order quickly surfaces the most common agents. A threat hunter should scrutinize agents with very low counts (potential custom tools) or known-malicious signatures (e.g., “sqlmap”, “nmap”). Cross-reference this list with a known-good baseline of user agents in your environment.
5. Identifying Suspicious Authentication Patterns
Failed authentication attempts, especially for specific high-value URLs, can indicate brute-force attacks or password spraying.
Verified Command:
SELECT [bash], [bash], [bash], [bash], COUNT() as Attempts FROM [bash] WHERE [bash] = 401 GROUP BY [bash], [bash], [bash], [bash] HAVING COUNT() > 5;
Step-by-step guide:
This query filters for HTTP 401 (Unauthorized) status codes. It then groups the results by user, client IP, and the URL they tried to access, counting the number of failed attempts. The `HAVING` clause filters out groups with more than 5 failures, which is a common threshold for identifying brute-force activity. Investigate any IP address generating a high volume of failures against login pages.
6. Correlating Activity by Client IP Address
Understanding all activity from a single IP address can reveal the scope of an attack, from reconnaissance to exploitation.
Verified Command:
SELECT [bash], [bash], [bash], [bash], [bash] FROM [bash] WHERE [bash] = '192.168.1.100' ORDER BY [bash];
Step-by-step guide:
Replace `’192.168.1.100’` with the IP address under investigation. This query returns a chronological timeline of all requests made by that IP. Look for progression from directory enumeration (many 404s) to accessing specific pages (200s), and finally to successful authentication (200 on a login page). This timeline is crucial for constructing the narrative of an attack.
7. Leveraging Log Parser Studio for Advanced Analysis
While command-line is powerful, GUI tools like Log Parser Studio (LPS) can accelerate complex query building and visualization.
Verified Command (LPS-compatible SQL):
SELECT TOP 10 ClientIP, COUNT() AS TotalRequests FROM '[bash]' WHERE UriStem LIKE '%.asp%' OR UriStem LIKE '%.aspx%' GROUP BY ClientIP ORDER BY TotalRequests DESC
Step-by-step guide:
This query, designed for use in LPS, identifies the top 10 IP addresses making the most requests to dynamic pages (ASP/ASPX). Attackers often target these pages for vulnerability exploitation. In LPS, you would replace `[bash]` with the path to your `.mdb` file. The graphical results grid and charting features make it easy to spot outliers and patterns that might be missed in a text-based output.
What Undercode Say:
- Forensic Goldmine Unexploited: The IIS UAL is a pervasive yet critically underutilized data source. Most enterprise security monitoring pipelines ignore it in favor of the basic IIS logs, creating a massive blind spot. Organizations that integrate UAL parsing into their threat-hunting workflows gain a significant advantage in detecting sophisticated, long-term intrusions.
- The Attacker’s Blind Spot: Sophisticated adversaries meticulously cover their tracks in standard logs but often forget or are unaware of the separate UAL data store. This makes UAL analysis a powerful technique for uncovering “low-and-slow” attacks that would otherwise blend into normal traffic. Hunting in UAL is effectively operating in a space where the adversary doesn’t expect you to be looking.
The technical barrier to parsing the proprietary `.mdb` format is the primary reason UAL is overlooked. However, as the commands above demonstrate, this barrier is easily overcome with basic scripting and SQL knowledge. The ROI for a threat hunter to learn these skills is immense, as it provides access to a detailed record of who accessed what and when, with a clarity that often surpasses standard logging. The future of defensive operations lies in leveraging all available data, not just the convenient ones.
Prediction:
The value of obscure data sources like IIS UAL will skyrocket in the coming years. As attackers continue to refine their techniques to evade detection in common logs, defenders will be forced to dig deeper into operating system and application telemetry. We predict a new class of security tools and EDR features will emerge, focused exclusively on aggregating and analyzing these “alternative” logs. Furthermore, advanced attacker tradecraft will evolve to include the targeted deletion or manipulation of UAL databases, making the ability to collect and secure this data proactively a critical component of future cyber defense strategies.
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IT/Security Reporter URL:
Reported By: Tasos Chatziefstratiou – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
