Detection rules › Sigma

Access To Chromium Browsers Sensitive Files By Uncommon Applications

Status
test
Severity
low
Log source
category file_access, product windows
Author
X__Junior (Nextron Systems)
Source
github.com/SigmaHQ/sigma

Detects file access requests to chromium based browser sensitive files by uncommon processes. Could indicate potential attempt of stealing sensitive information.

Known false positives

  • Antivirus, Anti-Spyware, Anti-Malware Software
  • Backup software
  • Legitimate software installed on partitions other than "C:\"
  • Searching software such as "everything.exe"

MITRE ATT&CK coverage

TacticTechniques
Credential Access

Rule body

title: Access To Chromium Browsers Sensitive Files By Uncommon Applications
id: c5f37810-a85f-4186-81e9-33f23abb4141
status: test
description: |
    Detects file access requests to chromium based browser sensitive files by uncommon processes.
    Could indicate potential attempt of stealing sensitive information.
references:
    - Internal Research
author: X__Junior (Nextron Systems)
date: 2024-07-29
tags:
    - attack.t1003
    - attack.credential-access
    - detection.threat-hunting
logsource:
    category: file_access
    product: windows
    definition: 'Requirements: Microsoft-Windows-Kernel-File ETW provider'
detection:
    selection:
        FileName|contains:
            - '\User Data\Default\Cookies'
            - '\User Data\Default\History'
            - '\User Data\Default\Network\Cookies'
            - '\User Data\Default\Web Data'
    filter_main_system:
        Image: System
    filter_main_generic:
        # This filter is added to avoid large amount of FP with 3rd party software. You should remove this in favour of specific filter per-application
        Image|startswith:
            - 'C:\Program Files (x86)\'
            - 'C:\Program Files\'
            - 'C:\Windows\system32\'
            - 'C:\Windows\SysWOW64\'
    filter_optional_defender:
        Image|startswith: 'C:\ProgramData\Microsoft\Windows Defender\'
        Image|endswith:
            - '\MpCopyAccelerator.exe'
            - '\MsMpEng.exe'
    condition: selection and not 1 of filter_main_* and not 1 of filter_optional_*
falsepositives:
    - Antivirus, Anti-Spyware, Anti-Malware Software
    - Backup software
    - Legitimate software installed on partitions other than "C:\"
    - Searching software such as "everything.exe"
level: low

Stages and Predicates

Stage 0: condition

selection and not 1 of filter_main_* and not 1 of filter_optional_*

Stage 1: selection

selection:
    FileName|contains:
        - '\User Data\Default\Cookies'
        - '\User Data\Default\History'
        - '\User Data\Default\Network\Cookies'
        - '\User Data\Default\Web Data'

Stage 2: not filter_main_*

filter_main_system:
    Image: System
filter_main_generic:
    Image|startswith:
        - 'C:\Program Files (x86)\'
        - 'C:\Program Files\'
        - 'C:\Windows\system32\'
        - 'C:\Windows\SysWOW64\'

Stage 3: not filter_optional_defender

filter_optional_defender:
    Image|startswith: 'C:\ProgramData\Microsoft\Windows Defender\'
    Image|endswith:
        - '\MpCopyAccelerator.exe'
        - '\MsMpEng.exe'

Exclusions

The rule actively suppresses these predicates.

FieldKindExcluded valuesSearch
ImageeqSystemexcludes:Image field:"Image" value:"System"
Imagestarts_withC:\Program Files (x86)\excludes:Image field:"Image" value:"C:\Program Files (x86)\"
Imagestarts_withC:\Program Files\excludes:Image field:"Image" value:"C:\Program Files\"
Imagestarts_withC:\Windows\SysWOW64\excludes:Image field:"Image" value:"C:\Windows\SysWOW64\"
Imagestarts_withC:\Windows\system32\excludes:Image field:"Image" value:"C:\Windows\system32\"
Imageends_with\MpCopyAccelerator.exeexcludes:Image field:"Image" value:"\MpCopyAccelerator.exe"
Imageends_with\MsMpEng.exeexcludes:Image field:"Image" value:"\MsMpEng.exe"
Imagestarts_withC:\ProgramData\Microsoft\Windows Defender\excludes:Image field:"Image" value:"C:\ProgramData\Microsoft\Windows Defender\"

Indicators

These rows show field, operator, and value matches.

FieldKindValuesSearch
FileNamematch
  • \User Data\Default\Cookies
  • \User Data\Default\History
  • \User Data\Default\Network\Cookies
  • \User Data\Default\Web Data
field:"file_name" kind:match