Uncommon Microsoft Office Trusted Location Added

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

Detects changes to registry keys related to "Trusted Location" of Microsoft Office where the path is set to something uncommon. Attackers might add additional trusted locations to avoid macro security restrictions.

MITRE ATT&CK coverage

Tactic	Techniques
Persistence	`T1112` Modify Registry
Defense Impairment	`T1112` Modify Registry

Event coverage

Provider	Event	Title
Sysmon	Event ID 13	RegistryEvent (Value Set)

Rule body yaml

title: Uncommon Microsoft Office Trusted Location Added
id: f742bde7-9528-42e5-bd82-84f51a8387d2
related:
    - id: a0bed973-45fa-4625-adb5-6ecdf9be70ac
      type: derived
status: test
description: Detects changes to registry keys related to "Trusted Location" of Microsoft Office where the path is set to something uncommon. Attackers might add additional trusted locations to avoid macro security restrictions.
references:
    - Internal Research
    - https://admx.help/?Category=Office2016&Policy=excel16.Office.Microsoft.Policies.Windows::L_TrustedLoc01
author: Nasreddine Bencherchali (Nextron Systems)
date: 2023-06-21
modified: 2023-09-29
tags:
    - attack.persistence
    - attack.defense-impairment
    - attack.t1112
logsource:
    category: registry_set
    product: windows
detection:
    selection:
        TargetObject|contains: 'Security\Trusted Locations\Location'
        TargetObject|endswith: '\Path'
    filter_exclude_known_paths:
        Details|contains:
            - '%APPDATA%\Microsoft\Templates'
            - '%%APPDATA%%\Microsoft\Templates'
            - '%APPDATA%\Microsoft\Word\Startup'
            - '%%APPDATA%%\Microsoft\Word\Startup'
            - ':\Program Files (x86)\Microsoft Office\root\Templates\'
            - ':\Program Files\Microsoft Office (x86)\Templates'
            - ':\Program Files\Microsoft Office\root\Templates\'
            - ':\Program Files\Microsoft Office\Templates\'
    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\'
    condition: selection and not 1 of filter_main_* and not 1 of filter_exclude_*
falsepositives:
    - Other unknown legitimate or custom paths need to be filtered to avoid false positives
level: high

Stages and Predicates

Stage 0: `condition`

selection and not 1 of filter_main_* and not 1 of filter_exclude_*

Stage 1: `selection`

selection:
    TargetObject|contains: 'Security\Trusted Locations\Location'
    TargetObject|endswith: '\Path'

Stage 2: `not filter_main_*`

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\'

Stage 3: `not filter_exclude_known_paths`

filter_exclude_known_paths:
    Details|contains:
        - '%APPDATA%\Microsoft\Templates'
        - '%%APPDATA%%\Microsoft\Templates'
        - '%APPDATA%\Microsoft\Word\Startup'
        - '%%APPDATA%%\Microsoft\Word\Startup'
        - ':\Program Files (x86)\Microsoft Office\root\Templates\'
        - ':\Program Files\Microsoft Office (x86)\Templates'
        - ':\Program Files\Microsoft Office\root\Templates\'
        - ':\Program Files\Microsoft Office\Templates\'

Exclusions

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

Field	Kind	Excluded values
`Image`	ends_with	`\OfficeClickToRun.exe`
`Image`	match	`:\Program Files\Common Files\Microsoft Shared\ClickToRun\`
`Image`	match	`:\Program Files (x86)\Microsoft Office\`
`Image`	match	`:\Program Files\Microsoft Office\`
`Details`	match	`%%APPDATA%%\Microsoft\Templates`
`Details`	match	`%%APPDATA%%\Microsoft\Word\Startup`
`Details`	match	`%APPDATA%\Microsoft\Templates`
`Details`	match	`%APPDATA%\Microsoft\Word\Startup`
`Details`	match	`:\Program Files (x86)\Microsoft Office\root\Templates\`
`Details`	match	`:\Program Files\Microsoft Office (x86)\Templates`
`Details`	match	`:\Program Files\Microsoft Office\Templates\`
`Details`	match	`:\Program Files\Microsoft Office\root\Templates\`

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
`TargetObject`	ends_with	`\Path` corpus 2 (sigma 2)
`TargetObject`	match	`Security\Trusted Locations\Location` corpus 2 (sigma 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)

Uncommon Microsoft Office Trusted Location Added

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection`

Stage 2: `not filter_main_*`

Stage 3: `not filter_exclude_known_paths`

Exclusions

Indicators

Keyboard shortcuts

Search operators

Uncommon Microsoft Office Trusted Location Added

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection

Stage 2: not filter_main_*

Stage 3: not filter_exclude_known_paths

Exclusions

Indicators

Stage 0: `condition`

Stage 1: `selection`

Stage 2: `not filter_main_*`

Stage 3: `not filter_exclude_known_paths`