| ID | Technique | Tactic |
|---|---|---|
| T1218.003 | CMSTP | Defense Evasion |
Detection: Windows Unusual Process Load Mozilla NSS-Mozglue Module
Description
The following analytic identifies processes loading Mozilla NSS-Mozglue libraries such as mozglue.dll and nss3.dll. It leverages Sysmon Event logs, specifically monitoring EventCode 7, which tracks image loaded events. This activity is significant because it can indicate unauthorized access or manipulation of these libraries, which are commonly used by Mozilla applications like Firefox and Thunderbird. If confirmed malicious, this could lead to data exfiltration, credential theft, or further compromise of the system.
Search
1`sysmon` EventCode=7 ImageLoaded IN ("*\\mozglue.dll", "*\\nss3.dll") NOT(process_path IN("*:\\Program Files\Mozilla Firefox\\firefox.exe", "*:\\Program Files (x86)\Mozilla Firefox\\firefox.exe", "*:\\Program Files\\Mozilla Thunderbird\\thunderbird.exe", "*:\\Program Files (x86)\\Mozilla Thunderbird\\thunderbird.exe", "*\\Tor Browser\\Browser\\firefox.exe","*:\\Program Files\\Code42\\CrashPlan\\Code42Service.exe", "*:\\Program Files (x86)\\Code42\\CrashPlan\\Code42Service.exe", "*:\\Program Files\\Pale Moon\\palemoon.exe", "*:\\Program Files (x86)\\Pale Moon\\palemoon.exe", "*:\\Program Files\\Waterfox\\waterfox.exe","*:\\Program Files (x86)\\Waterfox\\waterfox.exe", "*:\\Program Files\\Cyberfox\cyberfox.exe", "*:\\Program Files (x86)\\Cyberfox\\cyberfox.exe", "*\\AppData\\Local\\slack\\slack.exe", "*:\\Program Files (x86)\\VMware\\VMware Horizon View Client\\vmware-view.exe", "*:\\Program Files (x86)\\Dropbox\\Client\\Dropbox.exe", "*:\\Program Files\\Google\\Google Earth Pro\\client\\googleearth.exe"))
2| fillnull
3| stats count min(_time) as firstTime max(_time) as lastTime by Image ImageLoaded dest loaded_file loaded_file_path original_file_name process_exec process_guid process_hash process_id process_name process_path service_dll_signature_exists service_dll_signature_verified signature signature_id user_id vendor_product
4| `security_content_ctime(firstTime)`
5| `security_content_ctime(lastTime)`
6| `windows_unusual_process_load_mozilla_nss_mozglue_module_filter`
Data Source
| Name | Platform | Sourcetype | Source |
|---|---|---|---|
| Sysmon EventID 7 |  Windows |
'XmlWinEventLog' |
'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational' |
Macros Used
| Name | Value |
|---|---|
| security_content_ctime | convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$) |
| windows_unusual_process_load_mozilla_nss_mozglue_module_filter | search * |
windows_unusual_process_load_mozilla_nss_mozglue_module_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
Annotations
MITRE ATT&CK
Kill Chain Phases
NIST
CIS
Threat Actors
Exploitation
DE.AE
CIS 10
Default Configuration
This detection is configured by default in Splunk Enterprise Security to run with the following settings:
| Setting | Value |
|---|---|
| Disabled | true |
| Cron Schedule | 0 * * * * |
| Earliest Time | -70m@m |
| Latest Time | -10m@m |
| Schedule Window | auto |
| Creates Risk Event | True |
This configuration file applies to all detections of type anomaly. These detections will use Risk Based Alerting.
Implementation
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
Legitimate windows application that are not on the list loading this dll. Filter as needed.
Associated Analytic Story
Risk Based Analytics (RBA)
Risk Message:
a non Firefox or Thunderbird process $process_name$ with $process_id$ loaded the Mozilla NSS-Mozglue libraries on host $dest$.
| Risk Object | Risk Object Type | Risk Score | Threat Objects |
|---|---|---|---|
| dest | system | 30 | process_name |
References
Detection Testing
| Test Type | Status | Dataset | Source | Sourcetype |
|---|---|---|---|---|
| Validation | ✅ Passing | N/A | N/A | N/A |
| Unit | ✅ Passing | Dataset | XmlWinEventLog:Microsoft-Windows-Sysmon/Operational |
XmlWinEventLog |
| Integration | ✅ Passing | Dataset | XmlWinEventLog:Microsoft-Windows-Sysmon/Operational |
XmlWinEventLog |
Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI.
Alternatively you can replay a dataset into a Splunk Attack Range
Source: GitHub | Version: 1