WinAPI Function Calls Via PowerShell Scripts

Status: test
Severity: medium
Log source: product windows, category ps_script
Author: Nikita Nazarov, oscd.community, Nasreddine Bencherchali (Nextron Systems)
Source: github.com/SigmaHQ/sigma

Detects calls to WinAPI functions from PowerShell scripts. Attackers can often leverage these APIs to avoid detection based on typical PowerShell function calls. Use this rule as a basis to hunt for interesting scripts.

MITRE ATT&CK coverage

Tactic	Techniques
Execution	`T1059.001` Command and Scripting Interpreter: PowerShell, `T1106` Native API

Event coverage

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

Rule body yaml

title: WinAPI Function Calls Via PowerShell Scripts
id: 9f22ccd5-a435-453b-af96-bf99cbb594d4
related:
    - id: ba3f5c1b-6272-4119-9dbd-0bc8d21c2702
      type: similar
    - id: 03d83090-8cba-44a0-b02f-0b756a050306
      type: similar
    - id: 19d65a1c-8540-4140-8062-8eb00db0bba5
      type: similar
status: test
description: Detects calls to WinAPI functions from PowerShell scripts. Attackers can often leverage these APIs to avoid detection based on typical PowerShell function calls. Use this rule as a basis to hunt for interesting scripts.
references:
    - https://speakerdeck.com/heirhabarov/hunting-for-powershell-abuse
author: Nikita Nazarov, oscd.community, Nasreddine Bencherchali (Nextron Systems)
date: 2023-07-21
tags:
    - attack.execution
    - attack.t1059.001
    - attack.t1106
    - detection.threat-hunting
logsource:
    product: windows
    category: ps_script
    definition: 'Requirements: Script Block Logging must be enabled'
detection:
    selection:
        ScriptBlockText|contains:
            - 'AddSecurityPackage'
            - 'AdjustTokenPrivileges'
            - 'CloseHandle'
            - 'CreateProcessWithToken'
            - 'CreateRemoteThread'
            - 'CreateThread'
            - 'CreateUserThread'
            - 'DangerousGetHandle'
            - 'DuplicateTokenEx'
            - 'EnumerateSecurityPackages'
            - 'FreeLibrary'
            - 'GetDelegateForFunctionPointer'
            - 'GetLogonSessionData'
            - 'GetModuleHandle'
            - 'GetProcAddress'
            - 'GetProcessHandle'
            - 'GetTokenInformation'
            - 'ImpersonateLoggedOnUser'
            - 'LoadLibrary'
            - 'memcpy'
            - 'MiniDumpWriteDump'
            - 'OpenDesktop'
            - 'OpenProcess'
            - 'OpenProcessToken'
            - 'OpenThreadToken'
            - 'OpenWindowStation'
            - 'QueueUserApc'
            - 'ReadProcessMemory'
            - 'RevertToSelf'
            - 'RtlCreateUserThread'
            - 'SetThreadToken'
            - 'VirtualAlloc'
            - 'VirtualFree'
            - 'VirtualProtect'
            - 'WaitForSingleObject'
            - 'WriteInt32'
            - 'WriteProcessMemory'
            - 'ZeroFreeGlobalAllocUnicode'
    condition: selection
falsepositives:
    - This rule is mainly used for hunting and will generate quite a lot of false positives when applied in production. It's best combined with other fields such as the path of execution, the parent process, etc.
level: medium

Stages and Predicates

Stage 0: `condition`

selection

Stage 1: `selection`

selection:
    ScriptBlockText|contains:
        - 'AddSecurityPackage'
        - 'AdjustTokenPrivileges'
        - 'CloseHandle'
        - 'CreateProcessWithToken'
        - 'CreateRemoteThread'
        - 'CreateThread'
        - 'CreateUserThread'
        - 'DangerousGetHandle'
        - 'DuplicateTokenEx'
        - 'EnumerateSecurityPackages'
        - 'FreeLibrary'
        - 'GetDelegateForFunctionPointer'
        - 'GetLogonSessionData'
        - 'GetModuleHandle'
        - 'GetProcAddress'
        - 'GetProcessHandle'
        - 'GetTokenInformation'
        - 'ImpersonateLoggedOnUser'
        - 'LoadLibrary'
        - 'memcpy'
        - 'MiniDumpWriteDump'
        - 'OpenDesktop'
        - 'OpenProcess'
        - 'OpenProcessToken'
        - 'OpenThreadToken'
        - 'OpenWindowStation'
        - 'QueueUserApc'
        - 'ReadProcessMemory'
        - 'RevertToSelf'
        - 'RtlCreateUserThread'
        - 'SetThreadToken'
        - 'VirtualAlloc'
        - 'VirtualFree'
        - 'VirtualProtect'
        - 'WaitForSingleObject'
        - 'WriteInt32'
        - 'WriteProcessMemory'
        - 'ZeroFreeGlobalAllocUnicode'

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	`AddSecurityPackage` `AdjustTokenPrivileges` corpus 3 (sigma 3) `CloseHandle` corpus 2 (sigma 2) `CreateProcessWithToken` `CreateRemoteThread` corpus 2 (sigma 2) `CreateThread` `CreateUserThread` `DangerousGetHandle` `DuplicateTokenEx` corpus 2 (sigma 2) `EnumerateSecurityPackages` `FreeLibrary` `GetDelegateForFunctionPointer` corpus 2 (sigma 2) `GetLogonSessionData` `GetModuleHandle` `GetProcAddress` corpus 2 (sigma 1, splunk 1) `GetProcessHandle` `GetTokenInformation` `ImpersonateLoggedOnUser` `LoadLibrary` `MiniDumpWriteDump` corpus 2 (sigma 2) `OpenDesktop` `OpenProcess` corpus 2 (sigma 2) `OpenProcessToken` corpus 2 (sigma 2) `OpenThreadToken` `OpenWindowStation` `QueueUserApc` `ReadProcessMemory` corpus 2 (sigma 2) `RevertToSelf` `RtlCreateUserThread` `SetThreadToken` `VirtualAlloc` corpus 2 (sigma 2) `VirtualFree` corpus 2 (sigma 2) `VirtualProtect` `WaitForSingleObject` `WriteInt32` `WriteProcessMemory` corpus 2 (sigma 2) `ZeroFreeGlobalAllocUnicode` `memcpy`

`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)

WinAPI Function Calls Via PowerShell Scripts

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection`

Indicators

Keyboard shortcuts

Search operators

WinAPI Function Calls Via PowerShell Scripts

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection

Indicators

Stage 0: `condition`

Stage 1: `selection`