Access To Browser Credential Files By Uncommon Applications - Security

Status: test
Severity: low
Log source: product windows, service security
Author: Daniel Koifman (@Koifsec), Nasreddine Bencherchali
Source: github.com/SigmaHQ/sigma

Detects file access requests to browser credential stores by uncommon processes. Could indicate potential attempt of credential stealing This rule requires heavy baselining before usage.

MITRE ATT&CK coverage

Tactic	Techniques
Credential Access	`T1555.003` Credentials from Password Stores: Credentials from Web Browsers

Event coverage

Provider	Event	Title
Security-Auditing	Event ID 4663	An attempt was made to access an object.

Rule body yaml

title: Access To Browser Credential Files By Uncommon Applications - Security
id: 4b60e527-ec73-4b47-8cb3-f02ad927ca65
related:
    - id: 91cb43db-302a-47e3-b3c8-7ede481e27bf
      type: similar
status: test
description: |
    Detects file access requests to browser credential stores by uncommon processes. Could indicate potential attempt of credential stealing This rule requires heavy baselining before usage.
references:
    - https://ipurple.team/2024/09/10/browser-stored-credentials/
author: Daniel Koifman (@Koifsec), Nasreddine Bencherchali
date: 2024-10-21
tags:
    - attack.credential-access
    - attack.t1555.003
    - detection.threat-hunting
logsource:
    product: windows
    service: security
    definition: 'Requirements: Audit File System subcategory must be enabled. Additionally, each listed ObjectName must have "List folder/read data" auditing enabled.'
detection:
    selection_eid:
        EventID: 4663
        ObjectType: 'File'
        # Note: This AccessMask requires enhancements. As this access can be combined with other requests. It should include all possible outcomes where READ access and similar are part of it.
        AccessMask: '0x1'
    selection_browser_chromium:
        ObjectName|contains:
            - '\User Data\Default\Login Data'
            - '\User Data\Local State'
            - '\User Data\Default\Network\Cookies'
    selection_browser_firefox:
        FileName|endswith:
            - '\cookies.sqlite'
            - '\places.sqlite'
            - 'release\key3.db'  # Firefox
            - 'release\key4.db'  # Firefox
            - 'release\logins.json' # Firefox
    filter_main_system:
        ProcessName: 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
        ProcessName|startswith:
            - 'C:\Program Files (x86)\'
            - 'C:\Program Files\'
            - 'C:\Windows\system32\'
            - 'C:\Windows\SysWOW64\'
    filter_optional_defender:
        ProcessName|startswith: 'C:\ProgramData\Microsoft\Windows Defender\'
        ProcessName|endswith:
            - '\MpCopyAccelerator.exe'
            - '\MsMpEng.exe'
    condition: selection_eid and 1 of selection_browser_* and not 1 of filter_main_* and not 1 of filter_optional_*
falsepositives:
    - Unknown
level: low

Stages and Predicates

Stage 0: `condition`

selection_eid and 1 of selection_browser_* and not 1 of filter_main_* and not 1 of filter_optional_*

Stage 1: `selection_eid`

selection_eid:
    EventID: 4663
    ObjectType: 'File'
    AccessMask: '0x1'

Stage 2: `selection_browser_chromium`

selection_browser_chromium:
    ObjectName|contains:
        - '\User Data\Default\Login Data'
        - '\User Data\Local State'
        - '\User Data\Default\Network\Cookies'

Stage 3: `selection_browser_firefox`

selection_browser_firefox:
    FileName|endswith:
        - '\cookies.sqlite'
        - '\places.sqlite'
        - 'release\key3.db'
        - 'release\key4.db'
        - 'release\logins.json'

Stage 4: `not filter_main_*`

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

Stage 5: `not filter_optional_defender`

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

Exclusions

Top-level NOT(...) conjuncts: predicates this rule actively suppresses.

Field	Kind	Excluded values
`ProcessName`	eq	`System`
`ProcessName`	starts_with	`C:\Program Files (x86)\`
`ProcessName`	starts_with	`C:\Program Files\`
`ProcessName`	starts_with	`C:\Windows\SysWOW64\`
`ProcessName`	starts_with	`C:\Windows\system32\`
`ProcessName`	ends_with	`\MpCopyAccelerator.exe`
`ProcessName`	ends_with	`\MsMpEng.exe`
`ProcessName`	starts_with	`C:\ProgramData\Microsoft\Windows Defender\`

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

Field	Kind	Values
`AccessMask`	eq	`0x1` corpus 2 (sigma 1, splunk 1)
`FileName`	ends_with	`\cookies.sqlite` `\places.sqlite` `release\key3.db` `release\key4.db` `release\logins.json`
`ObjectName`	match	`\User Data\Default\Login Data` `\User Data\Default\Network\Cookies` `\User Data\Local State`
`ObjectType`	eq	`File` corpus 10 (sigma 8, splunk 2)

`j` / `k`	Scroll down / up
`d` / `u`	Half-page down / up
`gg` / `G`	Top / bottom
`h` / `l`	History back / forward
`f`	Follow link (`Shift` = new tab)
`/`	Focus search
`?`	Toggle this help
`↑` / `↓`	Navigate search results
`Enter`	Open highlighted result
`Esc`	Close results / dialog

`type:`	`events` / `rules` / `providers`
`vendor:`	`sigma` / `elastic` / `splunk` / `kusto` / `chronicle` (vendor name alone also works: `sigma:`, `kql:`, `secops:`…)
`tactic:`	TA-id, slug, or name: `credential_access`, `TA0006`
`technique:`	technique or sub-technique ID: `T1003`, `T1003.001` (alias `tech:`)
`severity:`	`critical` / `high` / `medium` / `low` / `informational` (alias `sev:`)
`risk_score`	Numeric comparison on the Elastic risk score (0 to 100): `risk_score>50`, `risk_score<=20`, `risk_score=99` (alias `risk`; Elastic rules only)
`stages:`	Rules with exactly N pipeline stages
`correlation:`	`single_event` / `sequence` / `alternatives` / `alternatives_cross_log` / `all_required` / `correlated`
`with:`	Co-occurrence event-id; stacks (`with:4624 with:4769`) to require all, while a comma list in one occurrence (`with:4624,4769`) is an either-or group. Implies multi-event
`like:`	Structural neighbors of a rule slug (equivalents + subsumption stricter / broader): `like:comsvcs_lsass_memory_dump-splunk-sysmon`
`groupby:`	Entity-grouping substring match against `group_by_keys`: `groupby:user`, `groupby:host`
`uses:`	Rules whose predicate tree touches the field (any kind, any value): `uses:CommandLine`
`excludes:`	Rules with top-level `not()` clauses on the field (FP whitelists): `excludes:ParentImage`
`field:` / `value:`	Predicate search; narrows rule cards to those with a matching leaf and drives the indicator tier. Unquoted = substring, wildcards allowed (`value:mimikatz`)
`indicator:`	Shorthand for `field:F value:V`: `indicator:Image=*\powershell.exe`
`kind:`	Filter by predicate kind. Narrows rule cards to those carrying a matching predicate leaf (`vendor:elastic kind:cidr_match`) and drives the indicator tier: `contains` / `starts_with` / `ends_with` / `regex` / `cidr` / `eq` / `in` … (operator aliases `op:`/`match:`)
`has:` / `no:`	`sample`, `field`, `notes`, `refs`, `trace`, `thirdparty`, `rule`, `pattern`, `timewindow`, `threshold`, `newterms`, `sigma`/`elastic`/`splunk`/`kusto`/`chronicle`
`-op:val`	Exclude matches; works on most operators but not `type:`/`like:`/`has:`/`no:` (use `no:<flag>` to exclude a rule flag): `tactic:execution -vendor:splunk`. Standalone `-kind:`/`-field:`/`-value:` drop every rule carrying a matching predicate leaf (`type:rules -kind:is_null`)
`field:"…"` / `value:"…"`	Quoted value = anchored exact match (also allows spaces): `value:"net user"`
`a,b`	Comma = OR inside one operator (`vendor:sigma,elastic`, `severity:high,critical`); repeating a facet merges the same way. `field:`/`value:` never split (literal commas)
`vendors:` / `stage:`	Singular and plural spellings fold to the canonical operator and value: `tactics:` = `tactic:`, `type:event` = `type:events`, `correlation:sequences` = `correlation:sequence`, `has:thresholds` = `has:threshold`
`"quoted phrase"`	Exact-match a multi-word phrase (free text)

Access To Browser Credential Files By Uncommon Applications - Security

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection_eid`

Stage 2: `selection_browser_chromium`

Stage 3: `selection_browser_firefox`

Stage 4: `not filter_main_*`

Stage 5: `not filter_optional_defender`

Exclusions

Indicators

Keyboard shortcuts

Search operators

Access To Browser Credential Files By Uncommon Applications - Security

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection_eid

Stage 2: selection_browser_chromium

Stage 3: selection_browser_firefox

Stage 4: not filter_main_*

Stage 5: not filter_optional_defender

Exclusions

Indicators

Stage 0: `condition`

Stage 1: `selection_eid`

Stage 2: `selection_browser_chromium`

Stage 3: `selection_browser_firefox`

Stage 4: `not filter_main_*`

Stage 5: `not filter_optional_defender`