Add: sigma rules (#175)

rules/sigma/windows/powershell/powershell_script/powershell_keylogging.yml

@@ -0,0 +1,31 @@
+
+title: Powershell Keylogging
+author: frack113
+date: 2021/07/30
+description: Adversaries may log user keystrokes to intercept credentials as the user
+  types them.
+detection:
+  SELECTION_1:
+    EventID: 4104
+  SELECTION_2:
+    ScriptBlockText: '*Get-Keystrokes*'
+  SELECTION_3:
+    ScriptBlockText: '*Get-ProcAddress user32.dll GetAsyncKeyState*'
+  SELECTION_4:
+    ScriptBlockText: '*Get-ProcAddress user32.dll GetForegroundWindow*'
+  condition: (SELECTION_1 and (SELECTION_2 or (SELECTION_3 and SELECTION_4)))
+falsepositives:
+- Unknown
+id: 34f90d3c-c297-49e9-b26d-911b05a4866c
+level: medium
+logsource:
+  definition: EnableScriptBlockLogging must be set to enable
+  product: windows
+  service: powershell
+references:
+- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1218/T1218.md
+- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1056.001/src/Get-Keystrokes.ps1
+status: experimental
+tags:
+- attack.collection
+- attack.t1056.001