[New Rule] PowerShell Share Enumeration Script (#2243)

* [New Rule] PowerShell Share Enumeration Script

* Move the rule to the correct folder

* Update discovery_posh_invoke_sharefinder.toml

* Update discovery_posh_invoke_sharefinder.toml

Co-authored-by: Mika Ayenson <Mikaayenson@users.noreply.github.com>
Co-authored-by: Colson Wilhoit <48036388+DefSecSentinel@users.noreply.github.com>

rules/windows/discovery_posh_invoke_sharefinder.toml

@@ -0,0 +1,102 @@
+[metadata]
+creation_date = "2022/08/17"
+maturity = "production"
+min_stack_comments = "New fields added: required_fields, related_integrations, setup"
+min_stack_version = "8.3.0"
+updated_date = "2022/08/17"
+
+[rule]
+author = ["Elastic"]
+description = """
+Detects scripts that contain PowerShell functions, structures, or Windows API functions related to windows share
+enumeration activities. Attackers, mainly ransomware groups, commonly identify and inspect network shares, looking for
+critical information for encryption and/or exfiltration.
+"""
+from = "now-9m"
+index = ["winlogbeat-*", "logs-windows.*"]
+language = "kuery"
+license = "Elastic License v2"
+name = "PowerShell Share Enumeration Script"
+note = """## Setup
+
+The 'PowerShell Script Block Logging' logging policy must 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://www.advintel.io/post/hunting-for-corporate-insurance-policies-indicators-of-ransom-exfiltrations",
+  "https://thedfirreport.com/2022/04/04/stolen-images-campaign-ends-in-conti-ransomware/",
+  "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 = "4c59cff1-b78a-41b8-a9f1-4231984d1fb6"
+severity = "medium"
+tags = ["Elastic", "Host", "Windows", "Threat Detection", "Discovery"]
+timestamp_override = "event.ingested"
+type = "query"
+
+query = '''
+event.category:process and
+  powershell.file.script_block_text:(
+    "Invoke-ShareFinder" or
+    "Invoke-ShareFinderThreaded" or
+    (
+      "shi1_netname" and
+      "shi1_remark"
+    ) or
+    (
+      "NetShareEnum" and
+      "NetApiBufferFree"
+    )
+  )
+'''
+
+
+[[rule.threat]]
+framework = "MITRE ATT&CK"
+
+[[rule.threat.technique]]
+id = "T1135"
+name = "Network Share Discovery"
+reference = "https://attack.mitre.org/techniques/T1135/"
+
+[rule.threat.tactic]
+id = "TA0007"
+name = "Discovery"
+reference = "https://attack.mitre.org/tactics/TA0007/"
+
+[[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"
+