ID | Technique | Tactic |
---|---|---|
T1505 | Server Software Component | Persistence |
T1505.003 | Web Shell | Persistence |
T1190 | Exploit Public-Facing Application | Initial Access |
T1133 | External Remote Services | Initial Access |
Detection: Detect Exchange Web Shell
Description
The following analytic identifies the creation of suspicious .aspx files in known drop locations for Exchange exploitation, specifically targeting paths associated with HAFNIUM group and vulnerabilities like ProxyShell and ProxyNotShell. It leverages data from the Endpoint datamodel, focusing on process and filesystem events. This activity is significant as it may indicate a web shell deployment, a common method for persistent access and remote code execution. If confirmed malicious, attackers could gain unauthorized access, execute arbitrary commands, and potentially escalate privileges within the Exchange environment.
Search
1
2| tstats `security_content_summariesonly` count FROM datamodel=Endpoint.Processes where Processes.process_name=System by _time span=1h Processes.process_id Processes.process_name Processes.dest Processes.user
3| `drop_dm_object_name(Processes)`
4| join process_guid, _time [
5| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Filesystem where Filesystem.file_path IN ("*\\HttpProxy\\owa\\auth\\*", "*\\inetpub\\wwwroot\\aspnet_client\\*", "*\\HttpProxy\\OAB\\*") Filesystem.file_name IN( "*.aspx", "*.ashx") by _time span=1h Filesystem.user Filesystem.dest Filesystem.file_create_time Filesystem.file_name Filesystem.file_path
6| `drop_dm_object_name(Filesystem)`
7| fields _time dest user file_create_time file_name file_path process_name process_path process]
8| dedup file_create_time
9| table dest user file_create_time, file_name, file_path, process_name
10| `detect_exchange_web_shell_filter`
Data Source
Name | Platform | Sourcetype | Source |
---|---|---|---|
Sysmon EventID 1 | Windows | 'xmlwineventlog' |
'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational' |
Sysmon EventID 11 | Windows | 'xmlwineventlog' |
'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational' |
Macros Used
Name | Value |
---|---|
security_content_summariesonly | summariesonly= summariesonly_config allow_old_summaries= oldsummaries_config fillnull_value= fillnull_config`` |
detect_exchange_web_shell_filter | search * |
detect_exchange_web_shell_filter
is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
Annotations
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 Notable | Yes |
Rule Title | %name% |
Rule Description | %description% |
Notable Event Fields | user, dest |
Creates Risk Event | True |
Implementation
To successfully implement this search you need to be ingesting information on process that include the name of the process responsible for the changes from your endpoints into the Endpoint
datamodel in the Processes
node and Filesystem
node.
Known False Positives
The query is structured in a way that action
(read, create) is not defined. Review the results of this query, filter, and tune as necessary. It may be necessary to generate this query specific to your endpoint product.
Associated Analytic Story
Risk Based Analytics (RBA)
Risk Message | Risk Score | Impact | Confidence |
---|---|---|---|
A file - $file_name$ was written to disk that is related to IIS exploitation previously performed by HAFNIUM. Review further file modifications on endpoint $dest$ by user $user$. | 81 | 90 | 90 |
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: 7