Detection: Nishang PowershellTCPOneLine

Description

The following analytic detects the use of the Nishang Invoke-PowerShellTCPOneLine utility, which initiates a callback to a remote Command and Control (C2) server. It leverages Endpoint Detection and Response (EDR) data, focusing on PowerShell processes that include specific .NET classes like Net.Sockets.TCPClient and System.Text.ASCIIEncoding. This activity is significant as it indicates potential remote control or data exfiltration attempts by an attacker. If confirmed malicious, this could lead to unauthorized remote access, data theft, or further compromise of the affected system.

Search

1
2| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where `process_powershell` (Processes.process=*Net.Sockets.TCPClient* AND Processes.process=*System.Text.ASCIIEncoding*) by Processes.dest Processes.user Processes.parent_process Processes.original_file_name Processes.process_name Processes.process Processes.process_id Processes.parent_process_id 
3| `drop_dm_object_name(Processes)` 
4| `security_content_ctime(firstTime)`
5| `security_content_ctime(lastTime)`
6| `nishang_powershelltcponeline_filter`

Data Source

Name	Platform	Sourcetype	Source
CrowdStrike ProcessRollup2	N/A	'crowdstrike:events:sensor'	'crowdstrike'
Sysmon EventID 1	Windows	'xmlwineventlog'	'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'
Windows Event Log Security 4688	Windows	'xmlwineventlog'	'XmlWinEventLog:Security'

Macros Used

Annotations

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Implementation

The detection is based on data that originates from Endpoint Detection and Response (EDR) agents. These agents are designed to provide security-related telemetry from the endpoints where the agent is installed. To implement this search, you must ingest logs that contain the process GUID, process name, and parent process. Additionally, you must ingest complete command-line executions. These logs must be processed using the appropriate Splunk Technology Add-ons that are specific to the EDR product. The logs must also be mapped to the Processes node of the Endpoint data model. Use the Splunk Common Information Model (CIM) to normalize the field names and speed up the data modeling process.

Known False Positives

Limited false positives may be present. Filter as needed based on initial analysis.

Associated Analytic Story

• HAFNIUM Group

Risk Based Analytics (RBA)

References

• https://github.com/samratashok/nishang/blob/master/Shells/Invoke-PowerShellTcpOneLine.ps1

• https://www.volexity.com/blog/2021/03/02/active-exploitation-of-microsoft-exchange-zero-day-vulnerabilities/

• https://www.microsoft.com/security/blog/2021/03/02/hafnium-targeting-exchange-servers/

• https://www.rapid7.com/blog/post/2021/03/03/rapid7s-insightidr-enables-detection-and-response-to-microsoft-exchange-0-day/

Detection Testing

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: 4