SearchIndexer suspicious process activity

Status: experimental
Severity: medium
Log source: product windows, category process_creation
Author: mdecrevoisier
Source: github.com/mdecrevoisier/SIGMA-detection-rules

Detects scenarios where SearchIndexer spwaned another process with the same name, or when SearchIndexer process exists in an unexpected directory.

MITRE ATT&CK coverage

Tactic	Techniques
Stealth	`T1036` Masquerading

Event coverage

Provider	Event	Title
Sysmon	Event ID 1	Process creation
Security-Auditing	Event ID 4688	A new process has been created.

Rule body yaml

title: SearchIndexer suspicious process activity
description: Detects scenarios where SearchIndexer spwaned another process with the same name, or when SearchIndexer process exists in an unexpected directory.
references:
- https://securityaffairs.co/wordpress/75782/cyber-crime/hacking-hacker-botnet.html
- https://www.joesandbox.com/analysis/213580/1/html
- https://www.virustotal.com/gui/file/eb8417d0cf40160474faf587f3e1fdf94a0a2c9636ad1cf32005ff29ef3852dc
- https://www.filescan.io/uploads/62ad24c8473553ed319b5fe3/reports/104d3e08-1bdb-43ce-beb8-07c5688cef03/details
- https://any.run/report/eb8417d0cf40160474faf587f3e1fdf94a0a2c9636ad1cf32005ff29ef3852dc/c323438a-a3ec-4dcc-b304-dc47882a1eab
tags:
- attack.defense_evasion
- attack.t1036 # masquerading
author: mdecrevoisier
status: experimental
logsource:
  product: windows
  category: process_creation
detection:

  selection_parent_image:
    ParentImage|endswith: '\SearchIndexer.exe' 

  selection_image:
    Image|endswith: '\SearchIndexer.exe'

  selection_image_path:
    Image: 'C:\WINDOWS\system32\SearchIndexer.exe'

  selection_commandline:
    CommandLine|contains: 'c1 c2 c3 c4 c5 c6 c7 c8'

  condition: (selection_parent_image and selection_image) or (selection_image and not selection_image_path) or (selection_image and selection_commandline)
falsepositives:
- None 
level: medium

Stages and Predicates

Stage 0: `condition`

(selection_parent_image and selection_image) or (selection_image and not selection_image_path) or (selection_image and selection_commandline)

Stage 1: `selection_parent_image`

selection_parent_image:
  ParentImage|endswith: '\SearchIndexer.exe'

Stage 2: `selection_image`

selection_image:
  Image|endswith: '\SearchIndexer.exe'

Stage 3: `selection_image`

selection_image:
  Image|endswith: '\SearchIndexer.exe'

Stage 4: `not selection_image_path`

selection_image_path:
  Image: 'C:\WINDOWS\system32\SearchIndexer.exe'

Stage 5: `selection_image`

selection_image:
  Image|endswith: '\SearchIndexer.exe'

Stage 6: `selection_commandline`

selection_commandline:
  CommandLine|contains: 'c1 c2 c3 c4 c5 c6 c7 c8'

Exclusions

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

Field	Kind	Excluded values
`Image`	eq	`C:\WINDOWS\system32\SearchIndexer.exe`

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
`CommandLine`	match	`c1 c2 c3 c4 c5 c6 c7 c8`
`Image`	ends_with	`\SearchIndexer.exe`
`ParentImage`	ends_with	`\SearchIndexer.exe` corpus 3 (sigma 3)

`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)

SearchIndexer suspicious process activity

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection_parent_image`

Stage 2: `selection_image`

Stage 3: `selection_image`

Stage 4: `not selection_image_path`

Stage 5: `selection_image`

Stage 6: `selection_commandline`

Exclusions

Indicators

Keyboard shortcuts

Search operators

SearchIndexer suspicious process activity

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection_parent_image

Stage 2: selection_image

Stage 3: selection_image

Stage 4: not selection_image_path

Stage 5: selection_image

Stage 6: selection_commandline

Exclusions

Indicators

Stage 0: `condition`

Stage 1: `selection_parent_image`

Stage 2: `selection_image`

Stage 3: `selection_image`

Stage 4: `not selection_image_path`

Stage 5: `selection_image`

Stage 6: `selection_commandline`