title: ProxyLogon MSExchange OabVirtualDirectory
id: 550d3350-bb8a-4ff3-9533-2ba533f4a1c0
status: test
description: Detects specific patterns found after a successful ProxyLogon exploitation in relation to a Commandlet invocation of Set-OabVirtualDirectory
references:
- https://bi-zone.medium.com/hunting-down-ms-exchange-attacks-part-1-proxylogon-cve-2021-26855-26858-27065-26857-6e885c5f197c
author: Florian Roth (Nextron Systems)
date: 2021-08-09
modified: 2023-01-23
tags:
- attack.t1587.001
- attack.resource-development
logsource:
product: windows
service: msexchange-management
detection:
keywords_cmdlet:
'|all':
- 'OabVirtualDirectory'
- ' -ExternalUrl '
keywords_params:
- 'eval(request'
- 'http://f/<script'
- '"unsafe"};'
- 'function Page_Load()'
condition: keywords_cmdlet and keywords_params
falsepositives:
- Unlikely
level: critical
title: PUA - CsExec Execution
id: d08a2711-ee8b-4323-bdec-b7d85e892b31
status: test
description: Detects the use of the lesser known remote execution tool named CsExec a PsExec alternative
references:
- https://github.com/malcomvetter/CSExec
- https://www.microsoft.com/security/blog/2022/05/09/ransomware-as-a-service-understanding-the-cybercrime-gig-economy-and-how-to-protect-yourself/
author: Florian Roth (Nextron Systems)
date: 2022-08-22
modified: 2023-02-21
tags:
- attack.resource-development
- attack.t1587.001
- attack.execution
- attack.t1569.002
logsource:
category: process_creation
product: windows
detection:
selection:
Image|endswith: '\csexec.exe'
selection_pe:
Description: 'csexec'
condition: 1 of selection*
falsepositives:
- Unknown
level: high
title: Potential Privilege Escalation To LOCAL SYSTEM
id: 207b0396-3689-42d9-8399-4222658efc99
related:
- id: 8834e2f7-6b4b-4f09-8906-d2276470ee23 # PsExec specific rule
type: similar
status: test
description: Detects unknown program using commandline flags usually used by tools such as PsExec and PAExec to start programs with SYSTEM Privileges
references:
- https://learn.microsoft.com/en-us/sysinternals/downloads/psexec
- https://www.poweradmin.com/paexec/
- https://www.fireeye.com/blog/threat-research/2020/10/kegtap-and-singlemalt-with-a-ransomware-chaser.html
author: Florian Roth (Nextron Systems), Nasreddine Bencherchali (Nextron Systems)
date: 2021-05-22
modified: 2024-03-05
tags:
- attack.resource-development
- attack.t1587.001
logsource:
category: process_creation
product: windows
detection:
selection:
# Escalation to LOCAL_SYSTEM
CommandLine|contains|windash:
# Note that you don't need to add the ".exe" part when using psexec/paexec
# The "-" can also be replaced with "/"
# The order of args isn't important
# "cmd" can be replaced by "powershell", "pwsh" or any other console like software
- ' -s cmd'
- ' -s -i cmd'
- ' -i -s cmd'
# Pwsh (For PowerShell 7)
- ' -s pwsh'
- ' -s -i pwsh'
- ' -i -s pwsh'
# PowerShell (For PowerShell 5)
- ' -s powershell'
- ' -s -i powershell'
- ' -i -s powershell'
filter_main_exclude_coverage:
# This filter exclude strings covered by 8834e2f7-6b4b-4f09-8906-d2276470ee23
CommandLine|contains:
- 'paexec'
- 'PsExec'
- 'accepteula'
condition: selection and not 1 of filter_main_*
falsepositives:
- Weird admins that rename their tools
- Software companies that bundle PsExec/PAExec with their software and rename it, so that it is less embarrassing
level: high
title: Potential PsExec Remote Execution
id: ea011323-7045-460b-b2d7-0f7442ea6b38
status: test
description: Detects potential psexec command that initiate execution on a remote systems via common commandline flags used by the utility
references:
- https://learn.microsoft.com/en-us/sysinternals/downloads/psexec
- https://www.poweradmin.com/paexec/
- https://www.fireeye.com/blog/threat-research/2020/10/kegtap-and-singlemalt-with-a-ransomware-chaser.html
author: Florian Roth (Nextron Systems), Nasreddine Bencherchali (Nextron Systems)
date: 2023-02-28
modified: 2025-09-01
tags:
- attack.resource-development
- attack.t1587.001
logsource:
category: process_creation
product: windows
detection:
selection:
# Accepting EULA in commandline - often used in automated attacks
CommandLine|contains|all:
- 'accepteula'
- ' -u '
- ' -p '
- ' \\\\'
filter_main_localhost:
CommandLine|contains:
- '\\\\localhost'
- '\\\\127.'
condition: selection and not 1 of filter_main_*
falsepositives:
- Unknown
level: high
title: PsExec/PAExec Escalation to LOCAL SYSTEM
id: 8834e2f7-6b4b-4f09-8906-d2276470ee23
related:
- id: 207b0396-3689-42d9-8399-4222658efc99 # Generic rule based on similar cli flags
type: similar
status: test
description: Detects suspicious commandline flags used by PsExec and PAExec to escalate a command line to LOCAL_SYSTEM rights
references:
- https://learn.microsoft.com/en-us/sysinternals/downloads/psexec
- https://www.poweradmin.com/paexec/
- https://www.fireeye.com/blog/threat-research/2020/10/kegtap-and-singlemalt-with-a-ransomware-chaser.html
author: Florian Roth (Nextron Systems), Nasreddine Bencherchali (Nextron Systems)
date: 2021-11-23
modified: 2024-03-05
tags:
- attack.resource-development
- attack.t1587.001
logsource:
category: process_creation
product: windows
detection:
selection_sys: # Escalation to LOCAL_SYSTEM
CommandLine|contains|windash:
# Note that you don't need to add the ".exe" part when using psexec/paexec
# The "-" can also be replaced with "/"
# The order of args isn't important
# "cmd" can be replaced by "powershell", "pwsh" or any other console like software
- ' -s cmd'
- ' -s -i cmd'
- ' -i -s cmd'
# Pwsh (For PowerShell 7)
- ' -s pwsh'
- ' -s -i pwsh'
- ' -i -s pwsh'
# PowerShell (For PowerShell 5)
- ' -s powershell'
- ' -s -i powershell'
- ' -i -s powershell'
selection_other:
CommandLine|contains:
- 'psexec'
- 'paexec'
- 'accepteula'
condition: all of selection_*
falsepositives:
- Admins that use PsExec or PAExec to escalate to the SYSTEM account for maintenance purposes (rare)
- Users that debug Microsoft Intune issues using the commands mentioned in the official documentation; see https://learn.microsoft.com/en-us/mem/intune/apps/intune-management-extension
level: high
title: Uncommon File Created In Office Startup Folder
id: a10a2c40-2c4d-49f8-b557-1a946bc55d9d
status: test
description: Detects the creation of a file with an uncommon extension in an Office application startup folder
references:
- https://app.any.run/tasks/d6fe6624-6ef8-485d-aa75-3d1bdda2a08c/
- http://addbalance.com/word/startup.htm
- https://answers.microsoft.com/en-us/msoffice/forum/all/document-in-word-startup-folder-doesnt-open-when/44ab0932-2917-4150-8cdc-2f2cf39e86f3
- https://en.wikipedia.org/wiki/List_of_Microsoft_Office_filename_extensions
author: frack113, Nasreddine Bencherchali (Nextron Systems)
date: 2022-06-05
modified: 2023-12-13
tags:
- attack.resource-development
- attack.t1587.001
logsource:
product: windows
category: file_event
detection:
selection_word_paths:
- TargetFilename|contains: '\Microsoft\Word\STARTUP'
- TargetFilename|contains|all:
- '\Office'
- '\Program Files'
- '\STARTUP'
filter_exclude_word_ext:
TargetFilename|endswith:
- '.docb' # Word binary document introduced in Microsoft Office 2007
- '.docm' # Word macro-enabled document; same as docx, but may contain macros and scripts
- '.docx' # Word document
- '.dotm' # Word macro-enabled template; same as dotx, but may contain macros and scripts
- '.mdb' # MS Access DB
- '.mdw' # MS Access DB
- '.pdf' # PDF documents
- '.wll' # Word add-in
- '.wwl' # Word add-in
selection_excel_paths:
- TargetFilename|contains: '\Microsoft\Excel\XLSTART'
- TargetFilename|contains|all:
- '\Office'
- '\Program Files'
- '\XLSTART'
filter_exclude_excel_ext:
TargetFilename|endswith:
- '.xll'
- '.xls'
- '.xlsm'
- '.xlsx'
- '.xlt'
- '.xltm'
- '.xlw'
filter_main_office_click_to_run:
Image|contains: ':\Program Files\Common Files\Microsoft Shared\ClickToRun\'
Image|endswith: '\OfficeClickToRun.exe'
filter_main_office_apps:
Image|contains:
- ':\Program Files\Microsoft Office\'
- ':\Program Files (x86)\Microsoft Office\'
Image|endswith:
- '\winword.exe'
- '\excel.exe'
condition: ((selection_word_paths and not filter_exclude_word_ext) or (selection_excel_paths and not filter_exclude_excel_ext)) and not 1 of filter_main_*
falsepositives:
- False positive might stem from rare extensions used by other Office utilities.
level: high
title: VHD Image Download Via Browser
id: 8468111a-ef07-4654-903b-b863a80bbc95
status: test
description: |
Detects creation of ".vhd"/".vhdx" files by browser processes.
Malware can use mountable Virtual Hard Disk ".vhd" files to encapsulate payloads and evade security controls.
references:
- https://redcanary.com/blog/intelligence-insights-october-2021/
- https://www.kaspersky.com/blog/lazarus-vhd-ransomware/36559/
- https://securelist.com/lazarus-on-the-hunt-for-big-game/97757/
author: frack113, Christopher Peacock '@securepeacock', SCYTHE '@scythe_io'
date: 2021-10-25
modified: 2023-05-05
tags:
- attack.resource-development
- attack.t1587.001
logsource:
category: file_event
product: windows
detection:
selection:
Image|endswith:
- '\brave.exe'
- '\chrome.exe'
- '\firefox.exe'
- '\iexplore.exe'
- '\maxthon.exe'
- '\MicrosoftEdge.exe'
- '\msedge.exe'
- '\msedgewebview2.exe'
- '\opera.exe'
- '\safari.exe'
- '\seamonkey.exe'
- '\vivaldi.exe'
- '\whale.exe'
# We don't use "endswith" to also match with ADS logs and ".vhdx". Example: "TargetFilename: C:\Users\xxx\Downloads\windows.vhd:Zone.Identifier"
TargetFilename|contains: '.vhd'
condition: selection
falsepositives:
- Legitimate downloads of ".vhd" files would also trigger this
level: medium