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Sigma rules for CVE-2021-43808

7 rules · scoped to cve · back to CVE-2021-43808
Direct rules mention this entity in their title or description. Related rules cover the techniques this entity is known to use.
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Detection rules

7 of 7
direct critical
Antivirus Exploitation Framework Detection
Detects a highly relevant Antivirus alert that reports an exploitation framework. This event must not be ignored just because the AV has blocked the malware but investigate, how it came there in the first place.
status stable author Florian Roth (Nextron Systems), Arnim Rupp id 238527ad-3c2c-4e4f-a1f6-92fd63adb864 license Sigma · DRL-1.1
view Sigma YAML 
title: Antivirus Exploitation Framework Detection
id: 238527ad-3c2c-4e4f-a1f6-92fd63adb864
status: stable
description: |
    Detects a highly relevant Antivirus alert that reports an exploitation framework.
    This event must not be ignored just because the AV has blocked the malware but investigate, how it came there in the first place.
references:
    - https://www.nextron-systems.com/?s=antivirus
    - https://www.virustotal.com/gui/file/925b0b28472d4d79b4bf92050e38cc2b8f722691c713fc28743ac38551bc3797
    - https://www.virustotal.com/gui/file/8f8daabe1c8ceb5710949283818e16c4aa8059bf2ce345e2f2c90b8692978424
    - https://www.virustotal.com/gui/file/d9669f7e3eb3a9cdf6a750eeb2ba303b5ae148a43e36546896f1d1801e912466
author: Florian Roth (Nextron Systems), Arnim Rupp
date: 2018-09-09
modified: 2024-11-02
tags:
    - attack.execution
    - attack.t1203
    - attack.command-and-control
    - attack.t1219.002
logsource:
    category: antivirus
detection:
    selection:
        Signature|contains:
            - 'Backdoor.Cobalt'
            - 'Brutel'
            - 'BruteR'
            - 'CobaltStr'
            - 'CobaltStrike'
            - 'COBEACON'
            - 'Cometer'
            - 'Exploit.Script.CVE'
            - 'IISExchgSpawnCMD'
            - 'Metasploit'
            - 'Meterpreter'
            - 'MeteTool'
            - 'Mpreter'
            - 'MsfShell'
            - 'PowerSploit'
            - 'Razy'
            - 'Rozena'
            - 'Sbelt'
            - 'Seatbelt'
            - 'Sliver'
            - 'Swrort'
    condition: selection
falsepositives:
    - Unlikely
level: critical
direct high
Potential SpEL Injection In Spring Framework
Detects potential SpEL Injection exploitation, which may lead to RCE.
status test author Moti Harmats id e9edd087-89d8-48c9-b0b4-5b9bb10896b8 license Sigma · DRL-1.1
view Sigma YAML 
title: Potential SpEL Injection In Spring Framework
id: e9edd087-89d8-48c9-b0b4-5b9bb10896b8
status: test
description: Detects potential SpEL Injection exploitation, which may lead to RCE.
references:
    - https://owasp.org/www-community/vulnerabilities/Expression_Language_Injection
    - https://www.wix.engineering/post/threat-and-vulnerability-hunting-with-application-server-error-logs
author: Moti Harmats
date: 2023-02-11
tags:
    - attack.initial-access
    - attack.t1190
logsource:
    category: application
    product: spring
    definition: 'Requirements: application error logs must be collected (with LOG_LEVEL=ERROR and above)'
detection:
    keywords:
        - 'org.springframework.expression.ExpressionException'
    condition: keywords
falsepositives:
    - Application bugs
level: high
direct high
Exploit Framework User Agent
Detects suspicious user agent strings used by exploit / pentest frameworks like Metasploit in proxy logs
status test author Florian Roth (Nextron Systems) id fdd1bfb5-f60b-4a35-910e-f36ed3d0b32f license Sigma · DRL-1.1
view Sigma YAML 
title: Exploit Framework User Agent
id: fdd1bfb5-f60b-4a35-910e-f36ed3d0b32f
status: test
description: Detects suspicious user agent strings used by exploit / pentest frameworks like Metasploit in proxy logs
references:
    - https://blog.didierstevens.com/2015/03/16/quickpost-metasploit-user-agent-strings/
author: Florian Roth (Nextron Systems)
date: 2017-07-08
modified: 2025-01-18
tags:
    - attack.command-and-control
    - attack.t1071.001
logsource:
    category: proxy
detection:
    selection:
        c-useragent:
        # Cobalt Strike https://www.cobaltstrike.com/help-malleable-c2
            - 'Internet Explorer *'
            - 'Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; InfoPath.2)' # https://bluescreenofjeff.com/2016-06-28-cobalt-strike-http-c2-redirectors-with-apache-mod_rewrite/

        # Metasploit Framework - Analysis by Didier Stevens https://blog.didierstevens.com/2015/03/16/quickpost-metasploit-user-agent-strings/
            - 'Mozilla/4.0 (compatible; Metasploit RSPEC)'
            - 'Mozilla/4.0 (compatible; MSIE 6.1; Windows NT)'
            - 'Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1)' # old browser, rare, base-lining needed
            - 'Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0)' # old browser, rare, base-lining needed
            - 'Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.0; Trident/4.0)' # old browser, rare, base-lining needed
            - 'Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0; Trident/4.0; SIMBAR={7DB0F6DE-8DE7-4841-9084-28FA914B0F2E}; SLCC1; .N'
            - 'Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)' # only use in proxy logs - not for detection in web server logs
            - 'Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US) AppleWebKit/525.13 (KHTML, like Gecko) Chrome/4.0.221.6 Safari/525.13'
            - 'Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; WOW64; Trident/5.0; MAAU)' # Payloads

        # Metasploit Update by Florian Roth 08.07.2017
            - 'Mozilla/5.0'
            - 'Mozilla/4.0 (compatible; SPIPE/1.0'
        # - 'Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.1; Trident/6.0)'  # too many false positives expected
        # - 'Mozilla/5.0 (Windows NT 6.1; Trident/7.0; rv:11.0) like Gecko'  # too many false positives expected
            - 'Mozilla/5.0 (Windows NT 6.3; rv:39.0) Gecko/20100101 Firefox/35.0'
            - 'Sametime Community Agent' # Unknown if prone to false positives - https://github.com/rapid7/metasploit-framework/blob/97095ab3113de2f046e64a64c461a1f888554401/modules/exploits/windows/http/steamcast_useragent.rb
            - 'X-FORWARDED-FOR'
            - 'DotDotPwn v2.1'
            - 'SIPDROID'
            - 'Mozilla/5.0 (Windows NT 10.0; Win32; x32; rv:60.0)' # CobaltStrike https://unit42.paloaltonetworks.com/tracking-oceanlotus-new-downloader-kerrdown/

        # Empire
            - 'Mozilla/6.0 (X11; Linux x86_64; rv:24.0) Gecko/20140205     Firefox/27.0 Iceweasel/25.3.0'

        # Exploits
            - '*wordpress hash grabber*'
            - '*exploit*'

        # Havoc
            - 'Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/96.0.4664.110 Safari/537.36'  # https://github.com/HavocFramework/Havoc/issues/519
    condition: selection
falsepositives:
    - Unknown
level: high
direct medium
Ruby on Rails Framework Exceptions
Detects suspicious Ruby on Rails exceptions that could indicate exploitation attempts
status stable author Thomas Patzke id 0d2c3d4c-4b48-4ac3-8f23-ea845746bb1a license Sigma · DRL-1.1
view Sigma YAML 
title: Ruby on Rails Framework Exceptions
id: 0d2c3d4c-4b48-4ac3-8f23-ea845746bb1a
status: stable
description: Detects suspicious Ruby on Rails exceptions that could indicate exploitation attempts
references:
    - http://edgeguides.rubyonrails.org/security.html
    - http://guides.rubyonrails.org/action_controller_overview.html
    - https://stackoverflow.com/questions/25892194/does-rails-come-with-a-not-authorized-exception
    - https://github.com/rails/rails/blob/cd08e6bcc4cd8948fe01e0be1ea0c7ca60373a25/actionpack/lib/action_dispatch/middleware/exception_wrapper.rb
author: Thomas Patzke
date: 2017-08-06
modified: 2020-09-01
tags:
    - attack.initial-access
    - attack.t1190
logsource:
    category: application
    product: ruby_on_rails
detection:
    keywords:
        - ActionController::InvalidAuthenticityToken
        - ActionController::InvalidCrossOriginRequest
        - ActionController::MethodNotAllowed
        - ActionController::BadRequest
        - ActionController::ParameterMissing
    condition: keywords
falsepositives:
    - Application bugs
level: medium
direct medium
Django Framework Exceptions
Detects suspicious Django web application framework exceptions that could indicate exploitation attempts
status stable author Thomas Patzke id fd435618-981e-4a7c-81f8-f78ce480d616 license Sigma · DRL-1.1
view Sigma YAML 
title: Django Framework Exceptions
id: fd435618-981e-4a7c-81f8-f78ce480d616
status: stable
description: Detects suspicious Django web application framework exceptions that could indicate exploitation attempts
references:
    - https://docs.djangoproject.com/en/1.11/ref/exceptions/
    - https://docs.djangoproject.com/en/1.11/topics/logging/#django-security
author: Thomas Patzke
date: 2017-08-05
modified: 2020-09-01
tags:
    - attack.initial-access
    - attack.t1190
logsource:
    category: application
    product: django
detection:
    keywords:
        - SuspiciousOperation
        # Subclasses of SuspiciousOperation
        - DisallowedHost
        - DisallowedModelAdminLookup
        - DisallowedModelAdminToField
        - DisallowedRedirect
        - InvalidSessionKey
        - RequestDataTooBig
        - SuspiciousFileOperation
        - SuspiciousMultipartForm
        - SuspiciousSession
        - TooManyFieldsSent
        # Further security-related exceptions
        - PermissionDenied
    condition: keywords
falsepositives:
    - Application bugs
level: medium
direct medium
Spring Framework Exceptions
Detects suspicious Spring framework exceptions that could indicate exploitation attempts
status stable author Thomas Patzke id ae48ab93-45f7-4051-9dfe-5d30a3f78e33 license Sigma · DRL-1.1
view Sigma YAML 
title: Spring Framework Exceptions
id: ae48ab93-45f7-4051-9dfe-5d30a3f78e33
status: stable
description: Detects suspicious Spring framework exceptions that could indicate exploitation attempts
references:
    - https://docs.spring.io/spring-security/site/docs/current/api/overview-tree.html
author: Thomas Patzke
date: 2017-08-06
modified: 2020-09-01
tags:
    - attack.initial-access
    - attack.t1190
logsource:
    category: application
    product: spring
detection:
    keywords:
        - AccessDeniedException
        - CsrfException
        - InvalidCsrfTokenException
        - MissingCsrfTokenException
        - CookieTheftException
        - InvalidCookieException
        - RequestRejectedException
    condition: keywords
falsepositives:
    - Application bugs
level: medium
direct low
Windows MSIX Package Support Framework AI_STUBS Execution
Detects execution of Advanced Installer MSIX Package Support Framework (PSF) components, specifically AI_STUBS executables with original filename 'popupwrapper.exe'. This activity may indicate malicious MSIX packages build with Advanced Installer leveraging the Package Support Framework to bypass application control restrictions.
status experimental author Michael Haag, Swachchhanda Shrawan Poudel (Nextron Systems) id af5732ed-764e-489d-826d-0447c8b36242 license Sigma · DRL-1.1
view Sigma YAML 
title: Windows MSIX Package Support Framework AI_STUBS Execution
id: af5732ed-764e-489d-826d-0447c8b36242
status: experimental
description: |
    Detects execution of Advanced Installer MSIX Package Support Framework (PSF) components, specifically AI_STUBS executables with original filename 'popupwrapper.exe'.
    This activity may indicate malicious MSIX packages build with Advanced Installer leveraging the Package Support Framework to bypass application control restrictions.
references:
    - https://redcanary.com/blog/threat-intelligence/msix-installers/
    - https://redcanary.com/threat-detection-report/techniques/installer-packages/
    - https://learn.microsoft.com/en-us/windows/msix/package/package-support-framework
    - https://www.splunk.com/en_us/blog/security/msix-weaponization-threat-detection-splunk.html
author: Michael Haag, Swachchhanda Shrawan Poudel (Nextron Systems)
date: 2025-11-03
tags:
    - attack.execution
    - attack.stealth
    - attack.defense-impairment
    - attack.t1218
    - attack.t1553.005
    - attack.t1204.002
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith:
            - '\AI_STUBS\AiStubX64Elevated.exe'
            - '\AI_STUBS\AiStubX86Elevated.exe'
            - '\AI_STUBS\AiStubX64.exe'
            - '\AI_STUBS\AiStubX86.exe'
        OriginalFileName: 'popupwrapper.exe'
    condition: selection
falsepositives:
    - Legitimate applications packaged with Advanced Installer using Package Support Framework
level: low
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