Add: sigma rules (#175)

rules/sigma/windows/process_creation/sysmon_netcat_execution.yml

@@ -0,0 +1,33 @@
+
+title: Ncat Execution
+author: frack113
+date: 2021/07/21
+description: Adversaries may use a non-application layer protocol for communication
+  between host and C2 server or among infected hosts within a network
+detection:
+  SELECTION_1:
+    EventID: 1
+  SELECTION_2:
+    Image:
+    - '*\ncat.exe'
+  SELECTION_3:
+    CommandLine:
+    - '* -lvp *'
+    - '* -l --proxy-type http *'
+    - '* --exec cmd.exe *'
+    - '* -vnl --exec *'
+  condition: (SELECTION_1 and (SELECTION_2 or SELECTION_3))
+falsepositives:
+- Legitimate ncat use
+id: e31033fc-33f0-4020-9a16-faf9b31cbf08
+level: high
+logsource:
+  category: process_creation
+  product: windows
+references:
+- https://nmap.org/ncat/
+- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1095/T1095.md
+status: experimental
+tags:
+- attack.command_and_control
+- attack.t1095