[New Rule] PowerShell PSReflect Script (#1558)

rules/windows/execution_posh_psreflect.toml

@@ -0,0 +1,118 @@
+[metadata]
+creation_date = "2021/10/15"
+maturity = "production"
+updated_date = "2021/10/15"
+
+[rule]
+author = ["Elastic"]
+description = """
+Detects the use of PSReflect in PowerShell scripts. Attackers leverage PSReflect as a library that enables
+PowerShell to access win32 API functions.
+"""
+false_positives = ["Legitimate Powershell Scripts that make use of PSReflect to access the win32 API"]
+from = "now-9m"
+index = ["winlogbeat-*", "logs-windows.*"]
+language = "kuery"
+license = "Elastic License v2"
+name = "PowerShell PSReflect Script"
+note = """## Triage and analysis
+### Investigating PowerShell PSReflect Script
+
+PowerShell is one of the main tools in the belt of system administrators for automation, report routines, and other tasks.
+
+PSReflect is a library that enables PowerShell to access win32 API functions in an uncomplicated way. It also helps to
+create enums and structs easily—all without touching the disk.
+
+Although this is an interesting project for every developer and admin out there, it is mainly used in the red team and
+malware tooling for its capabilities.
+
+Detecting the core implementation of PSReflect means detecting most of the tooling that uses windows API through
+PowerShell, enabling the defender to discover tools being dropped in the environment.
+
+#### Possible investigation steps:
+- Check for additional PowerShell logs that indicate that the script/command was run.
+- Gather the script content that may be split into multiple script blocks, and identify its capabilities.
+- If the action is suspicious for the user, check for any other activities done by the user in the last 48 hours.
+- Look for additional alerts involving the host and the user.
+
+### False Positive Analysis
+- Verify whether the script content is malicious/harmful.
+
+### Related Rules
+- PowerShell Suspicious Discovery Related Windows API Functions - 61ac3638-40a3-44b2-855a-985636ca985e
+- PowerShell Keylogging Script - bd2c86a0-8b61-4457-ab38-96943984e889
+- PowerShell Suspicious Script with Audio Capture Capabilities - 2f2f4939-0b34-40c2-a0a3-844eb7889f43
+- Potential Process Injection via PowerShell - 2e29e96a-b67c-455a-afe4-de6183431d0d
+- PowerShell Reflection Assembly Load - e26f042e-c590-4e82-8e05-41e81bd822ad
+- PowerShell Suspicious Payload Encoded and Compressed - 81fe9dc6-a2d7-4192-a2d8-eed98afc766a
+- PowerShell Suspicious Script with Screenshot Capabilities - 959a7353-1129-4aa7-9084-30746b256a70
+
+### Response and Remediation
+- Immediate response should be taken to validate activity, investigate and potentially isolate activity to prevent further
+post-compromise behavior.
+
+## Config
+The 'PowerShell Script Block Logging' logging policy is required be configured (Enable).
+
+Steps to implement the logging policy with with Advanced Audit Configuration:
+```
+Computer Configuration > 
+Administrative Templates > 
+Windows PowerShell > 
+Turn on PowerShell Script Block Logging (Enable)
+```
+Steps to implement the logging policy via registry:
+```
+reg add "hklm\\SOFTWARE\\Policies\\Microsoft\\Windows\\PowerShell\\ScriptBlockLogging" /v EnableScriptBlockLogging /t REG_DWORD /d 1
+```
+"""
+references = [
+  "https://github.com/mattifestation/PSReflect/blob/master/PSReflect.psm1",
+  "https://github.com/atc-project/atc-data/blob/master/docs/Logging_Policies/LP_0109_windows_powershell_script_block_log.md"
+]
+risk_score = 47
+rule_id = "56f2e9b5-4803-4e44-a0a4-a52dc79d57fe"
+severity = "medium"
+tags = ["Elastic", "Host", "Windows", "Threat Detection", "Execution"]
+timestamp_override = "event.ingested"
+type = "query"
+
+query = '''
+event.category:process and 
+  powershell.file.script_block_text:(
+    New-InMemoryModule or
+    Add-Win32Type or
+    psenum or
+    DefineDynamicAssembly or
+    DefineDynamicModule or
+    Reflection.TypeAttributes or
+    Reflection.Emit.OpCodes or
+    Reflection.Emit.CustomAttributeBuilder or
+    Runtime.InteropServices.DllImportAttribute
+  )
+'''
+
+
+[[rule.threat]]
+framework = "MITRE ATT&CK"
+
+[[rule.threat.technique]]
+name = "Command and Scripting Interpreter"
+reference = "https://attack.mitre.org/techniques/T1059/"
+id = "T1059"
+
+    [[rule.threat.technique.subtechnique]]
+    name = "PowerShell"
+    reference = "https://attack.mitre.org/techniques/T1059/001/"
+    id = "T1059.001"
+
+[[rule.threat.technique]]
+name = "Native API"
+reference = "https://attack.mitre.org/techniques/T1106/"
+id = "T1106"
+
+[rule.threat.tactic]
+name = "Execution"
+reference = "https://attack.mitre.org/tactics/TA0002/"
+id = "TA0002"
+