The user of the Accounting workstation reported thattheir calculator repeatedly opens without their input.

To identify thefile namethat triggered theRuleName: Suspicious PowerShellon theaccounting-pcworkstation, follow these detailed steps:

Step 1: Access the SIEM System

Open your web browser and navigate to theSIEM dashboard.

Log in with youradministrator credentials.

Step 2: Set Up the Query

Go to theSearchorQuerysection of the SIEM.

Set theTime Rangeto thelast 24 hours.

Query Parameters:

Agent Name:accounting-pc

Rule Name:Suspicious PowerShell

Event Type:Startup items or Process creation

Step 3: Construct the SIEM Query

Here’s an example of how to construct the query:

Example Query (Splunk):

index=windows_logs

| search agent.name="accounting-pc" RuleName="Suspicious PowerShell"

| where _time > now() - 24h

| table _time, agent.name, process_name, file_path, RuleName

Example Query (Elastic SIEM):

{

"query": {

"bool": {

"must": [

{ "match": { "agent.name": "accounting-pc" }},

{ "match": { "RuleName": "Suspicious PowerShell" }},

{ "range": { "@timestamp": { "gte": "now-24h" }}}

]

}

}

}

Step 4: Analyze the Query Results

The query should return a table or list containing:

Time of Execution

Agent Name:accounting-pc

Process Name

File Path

Rule Name

Example Output:

_time

agent.name

process_name

file_path

RuleName

2024-04-07T10:45:23

accounting-pc

powershell.exe

C:\Users\Accounting\AppData\Roaming\calc.ps1

Suspicious PowerShell

Step 5: Identify the Suspicious File

Theprocess_namein the output showspowershell.exeexecuting a suspicious script.

Thefile pathindicates the script responsible:

makefile

C:\Users\Accounting\AppData\Roaming\calc.ps1

The suspicious script file is:

calc.ps1

Step 6: Confirm the Malicious Nature

Manual Inspection:

Navigate to the specified file path on theaccounting-pcworkstation.

Check the contents of calc.ps1 for any malicious PowerShell code.

Hash Verification:

Generate theSHA256 hashof the file and compare it with known malware signatures.

Answer:

calc.ps1

Step 7: Immediate Response

Isolate the Workstation:Disconnectaccounting-pcfrom the network.

Terminate the Malicious Process:

Stop the powershell.exe process running calc.ps1.

Use Task Manager or a script:

powershell

Stop-Process -Name "powershell" -Force

Remove the Malicious Script:

powershell

Remove-Item "C:\Users\Accounting\AppData\Roaming\calc.ps1" -Force

Scan for Persistence Mechanisms:

CheckStartup itemsandScheduled Tasksfor any references to calc.ps1.

Step 8: Documentation

Record the following:

Date and Time:When the incident was detected.

Affected Host:accounting-pc

Malicious File:calc.ps1

Actions Taken:File removal and process termination.