Certificate Exported Via PowerShell - ScriptBlock

Status: test
Severity: medium
Log source: product windows, category ps_script
Author: Florian Roth (Nextron Systems)
Source: github.com/SigmaHQ/sigma

Detects calls to cmdlets inside of PowerShell scripts that are used to export certificates from the local certificate store. Threat actors were seen abusing this to steal private keys from compromised machines.

MITRE ATT&CK coverage

Tactic	Techniques
Credential Access	`T1552.004` Unsecured Credentials: Private Keys

Event coverage

Provider	Event	Title
PowerShell	Event ID 4104	Creating Scriptblock text (MessageNumber of MessageTotal).

Rule body yaml

title: Certificate Exported Via PowerShell - ScriptBlock
id: aa7a3fce-bef5-4311-9cc1-5f04bb8c308c
related:
    - id: 9e716b33-63b2-46da-86a4-bd3c3b9b5dfb
      type: similar
status: test
description: Detects calls to cmdlets inside of PowerShell scripts that are used to export certificates from the local certificate store. Threat actors were seen abusing this to steal private keys from compromised machines.
references:
    - https://us-cert.cisa.gov/ncas/analysis-reports/ar21-112a
    - https://learn.microsoft.com/en-us/powershell/module/pki/export-pfxcertificate?view=windowsserver2022-ps
    - https://www.splunk.com/en_us/blog/security/breaking-the-chain-defending-against-certificate-services-abuse.html
author: Florian Roth (Nextron Systems)
date: 2021-04-23
modified: 2023-05-18
tags:
    - attack.credential-access
    - attack.t1552.004
logsource:
    product: windows
    category: ps_script
    definition: 'Requirements: Script Block Logging must be enabled'
detection:
    selection:
        ScriptBlockText|contains:
            - 'Export-PfxCertificate'
            - 'Export-Certificate'
    filter_optional_module_export:
        ScriptBlockText|contains: 'CmdletsToExport = @('
    condition: selection and not 1 of filter_optional_*
falsepositives:
    - Legitimate certificate exports by administrators. Additional filters might be required.
level: medium

Stages and Predicates

Stage 0: `condition`

selection and not 1 of filter_optional_*

Stage 1: `selection`

selection:
    ScriptBlockText|contains:
        - 'Export-PfxCertificate'
        - 'Export-Certificate'

Stage 2: `not filter_optional_module_export`

filter_optional_module_export:
    ScriptBlockText|contains: 'CmdletsToExport = @('

Exclusions

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

Field	Kind	Excluded values
`ScriptBlockText`	match	`CmdletsToExport = @(`

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
`ScriptBlockText`	match	`Export-Certificate` corpus 2 (sigma 1, splunk 1) `Export-PfxCertificate` corpus 2 (sigma 1, splunk 1)

`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)

Certificate Exported Via PowerShell - ScriptBlock

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection`

Stage 2: `not filter_optional_module_export`

Exclusions

Indicators

Keyboard shortcuts

Search operators

Certificate Exported Via PowerShell - ScriptBlock

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection

Stage 2: not filter_optional_module_export

Exclusions

Indicators

Stage 0: `condition`

Stage 1: `selection`

Stage 2: `not filter_optional_module_export`