Add: sigma rules (#175)

rules/sigma/windows/process_creation/win_powershell_bitsjob.yml

@@ -0,0 +1,33 @@
+
+title: Suspicious Bitsadmin Job via PowerShell
+author: Endgame, JHasenbusch (ported to sigma for oscd.community)
+date: 2018/10/30
+description: Detect download by BITS jobs via PowerShell
+detection:
+  SELECTION_1:
+    EventID: 1
+  SELECTION_2:
+    Image: '*\powershell.exe'
+  SELECTION_3:
+    CommandLine: '*Start-BitsTransfer*'
+  condition: (SELECTION_1 and SELECTION_2 and SELECTION_3)
+falsepositives:
+- Unknown
+fields:
+- ComputerName
+- User
+- CommandLine
+id: f67dbfce-93bc-440d-86ad-a95ae8858c90
+level: medium
+logsource:
+  category: process_creation
+  product: windows
+modified: 2019/11/11
+references:
+- https://eqllib.readthedocs.io/en/latest/analytics/ec5180c9-721a-460f-bddc-27539a284273.html
+- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1197/T1197.md
+status: experimental
+tags:
+- attack.defense_evasion
+- attack.persistence
+- attack.t1197