Email Exifiltration Via Powershell

Status: test
Severity: high
Log source: category process_creation, product windows
Author: Nasreddine Bencherchali (Nextron Systems), Azure-Sentinel (idea)
Source: github.com/SigmaHQ/sigma

Detects email exfiltration via powershell cmdlets

MITRE ATT&CK coverage

Tactic	Techniques
Exfiltration	No specific technique

Telemetry coverage

Provider	Record / event type
Sysmon	Event ID 1: Process creation
Security-Auditing	Event ID 4688: A new process has been created.

Rule body

title: Email Exifiltration Via Powershell
id: 312d0384-401c-4b8b-abdf-685ffba9a332
status: test
description: Detects email exfiltration via powershell cmdlets
references:
    - https://www.microsoft.com/security/blog/2022/09/07/profiling-dev-0270-phosphorus-ransomware-operations/
    - https://github.com/Azure/Azure-Sentinel/blob/7e6aa438e254d468feec061618a7877aa528ee9f/Hunting%20Queries/Microsoft%20365%20Defender/Ransomware/DEV-0270/Email%20data%20exfiltration%20via%20PowerShell.yaml
author: Nasreddine Bencherchali (Nextron Systems),  Azure-Sentinel (idea)
date: 2022-09-09
tags:
    - attack.exfiltration
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith:
            - '\powershell.exe'
            - '\pwsh.exe'
        CommandLine|contains|all:
            - 'Add-PSSnapin'
            - 'Get-Recipient'
            - '-ExpandProperty'
            - 'EmailAddresses'
            - 'SmtpAddress'
            - '-hidetableheaders'
    condition: selection
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: `condition`

selection

Stage 1: `selection`

selection:
    Image|endswith:
        - '\powershell.exe'
        - '\pwsh.exe'
    CommandLine|contains|all:
        - 'Add-PSSnapin'
        - 'Get-Recipient'
        - '-ExpandProperty'
        - 'EmailAddresses'
        - 'SmtpAddress'
        - '-hidetableheaders'

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`CommandLine`	match	`-ExpandProperty` corpus 2 (sigma 1, kusto 1) `-hidetableheaders` corpus 2 (sigma 1, kusto 1) `Add-PSSnapin` corpus 3 (sigma 2, kusto 1) `EmailAddresses` corpus 2 (sigma 1, kusto 1) `Get-Recipient` corpus 2 (sigma 1, kusto 1) `SmtpAddress` corpus 2 (sigma 1, kusto 1)	`field:"CommandLine" kind:match`
`Image`	ends_with	`\powershell.exe` corpus 179 (sigma 178, kusto 1) `\pwsh.exe` corpus 165 (sigma 164, kusto 1)	`field:"Image" kind:ends_with`

Email Exifiltration Via Powershell

MITRE ATT&CK coverage

Telemetry coverage

Rule body

Stages and Predicates

Stage 0: condition

Stage 1: selection

Indicators

Stage 0: `condition`

Stage 1: `selection`