Server Software Component: IIS Components T1505.004
Tactic: Persistence
Adversaries may install malicious components that run on Internet Information Services (IIS) web servers to establish persistence. IIS provides several mechanisms to extend the functionality of the web servers. For example, Internet Server Application Programming Interface (ISAPI) extensions and filters can be installed to examine and/or modify incoming and outgoing IIS web requests. Extensions and filters are deployed as DLL files that export three functions: Get{Extension/Filter}Version, Http{Extension/Filter}Proc, and (optionally) Terminate{Extension/Filter}. IIS modules may also be installed to extend IIS web servers.
Events covered
8 catalog events are tagged with this technique by at least one rule.
| Provider | Event | Title |
|---|---|---|
| Sysmon | Event ID 1 | Process creation |
| Sysmon | Event ID 11 | FileCreate |
| Security-Auditing | Event ID 4688 | A new process has been created. |
| IIS-Configuration | Event ID 29 | Changes to 'Configuration' at 'ConfigPath' have successfully been committed. |
| IIS-W3SVC-WP | Event ID 2282 | The Module DLL '%1' could not be loaded due to a configuration problem |
| PowerShell | Event ID 4103 | Payload Context: ContextInfo User Data: UserData. |
| PowerShell | Event ID 4104 | Creating Scriptblock text (MessageNumber of MessageTotal). |
| PowerShell | Event ID 800 | Event ID 800 |
Authoring guide
Patterns shared across the 22 rules above: which fields they filter on, what specific values they look for, and what they exclude. The catalog normalizes field names across vendors so Sigma's Image, Elastic's process.name, and Splunk's process_name collapse into one row. Each rule contributes at most once per row.
Fields filtered most (21 distinct)
The fields most rules look at when detecting this technique. The How column shows the operators authors use (eq, wildcard, regex_match, match) and how often each appears. Sample values are concrete examples to start from, not an exhaustive list.
Top indicator values (80 distinct)
Specific (field, operator, value) combinations the rules check for, ranked by how many rules under this technique use each one. The Corpus reach column counts how many rules across the entire catalog (any technique) check the same combination. High numbers point to widely-used indicators that are likely noisy on their own; combine them with another condition for useful signal. Blank means the combination is specific to rules under this technique. Click a value to expand the rules under this technique that use it.
Exclusions (16 distinct)
Field/operator/value combinations excluded by rules under this technique (top-level not() clauses), sorted by how many rules exclude each. These are the false-positive paths the community has learned to filter out. A new rule that ignores the high-count entries here will likely fire on the same noisy paths. Click a value to expand the rules under this technique that exclude it.
Rules under this technique
Every rule in the catalog tagged with this technique, grouped by vendor. Click a rule title for its full predicates, exclusions, and indicators.
Sigma 10 rules
- ETW Logging/Processing Option Disabled On IIS Server
- HTTP Logging Disabled On IIS Server
- New Module Module Added To IIS Server
- Previously Installed IIS Module Was Removed
- Suspicious IIS Module Registration
- Webserver IIS configuration edited (SYSMON)
- Webserver IIS module installed (command)
- Webserver IIS module installed (command)
- Webserver IIS module installed (PowerShell)
- Webserver IIS module installed via GAC manipulation (PowerShell)
Splunk 12 rules
- IIS Worker (W3WP) Spawn Command Line (Windows Event Log)
- Shell Spawned by Web Server - Windows (Windows Event Log)
- Windows Disable Windows Event Logging Disable HTTP Logging
- Windows IIS Components Add New Module
- Windows IIS Components Get-WebGlobalModule Module Query
- Windows IIS Components Module Failed to Load
- Windows IIS Components New Module Added
- Windows PowerShell Add Module to Global Assembly Cache
- Windows PowerShell Disable HTTP Logging
- Windows PowerShell IIS Components WebGlobalModule Usage
- Windows Server Software Component GACUtil Install to GAC
- Windows Shell or Script Execution From IIS Directory