Add: sigma rules (#175)

rules/sigma/windows/process_creation/win_exploit_systemnightmare.yml

@@ -0,0 +1,27 @@
+
+title: SystemNightmare Exploitation Script Execution
+author: Florian Roth
+date: 2021/08/11
+description: Detects the exploitation of PrinterNightmare to get a shell as LOCAL_SYSTEM
+detection:
+  SELECTION_1:
+    EventID: 1
+  SELECTION_2:
+    CommandLine:
+    - '*printnightmare.gentilkiwi.com*'
+    - '* /user:gentilguest *'
+    - '*Kiwi Legit Printer*'
+  condition: (SELECTION_1 and SELECTION_2)
+falsepositives:
+- Unknown
+id: c01f7bd6-0c1d-47aa-9c61-187b91273a16
+level: critical
+logsource:
+  category: process_creation
+  product: windows
+references:
+- https://github.com/GossiTheDog/SystemNightmare
+status: experimental
+tags:
+- attack.privilege_escalation
+- attack.t1068