The following hunting analytic identifies
msi.dll being loaded by a binary not located in
windows paths. This behavior is most recently related to InstallerFileTakeOver, or CVE-2021-41379, and DLL side-loading. CVE-2021-41379 requires a binary to be dropped and
msi.dll to be loaded by it. To Successful exploitation of this issue happens in four parts \
- Generation of an MSI that will trigger bad behavior. \
- Preparing a directory for MSI installation. \
- Inducing an error state. \
- Racing to introduce a junction and a symlink to trick msiexec.exe to modify the attacker specified file.
msi.dllhas been abused in DLL side-loading attacks by being loaded by non-system binaries.
- Type: Hunting
Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
- Last Updated: 2021-12-08
- Author: Michael Haag, Splunk
- ID: ccb98a66-5851-11ec-b91c-acde48001122
Kill Chain Phase
1 2 3 4 5 `sysmon` EventCode=7 ImageLoaded="*\\msi.dll" NOT (Image IN ("*\\System32\\*","*\\syswow64\\*","*\\windows\\*", "*\\winsxs\\*")) | stats count min(_time) as firstTime max(_time) as lastTime by Image ImageLoaded process_name Computer EventCode ProcessId | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `msi_module_loaded_by_non_system_binary_filter`
The SPL above uses the following Macros:
msi_module_loaded_by_non-system_binary_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
List of fields required to use this analytic.
How To Implement
To successfully implement this search, you need to be ingesting logs with the process name and imageloaded executions from your endpoints. If you are using Sysmon, you must have at least version 6.0.4 of the Sysmon TA.
Known False Positives
It is possible some Administrative utilities will load msi.dll outside of normal system paths, filter as needed.
Associated Analytic Story
|56.0||80||70||The following module $ImageLoaded$ was loaded by $Image$ outside of the normal system paths on endpoint $Computer$, potentally related to DLL side-loading.|
The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.
source | version: 1