Sync RTA Linux Powershell Egress Network Connection (#4202)

Co-authored-by: shashank-elastic <91139415+shashank-elastic@users.noreply.github.com>

rta/linux_execution_linux_powershell_outbound_network_connection.py

@@ -0,0 +1,59 @@
+# Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+# or more contributor license agreements. Licensed under the Elastic License
+# 2.0; you may not use this file except in compliance with the Elastic License
+# 2.0.
+
+import sys
+import subprocess
+import time
+
+from . import RtaMetadata, common
+
+metadata = RtaMetadata(
+    uuid="65978ab7-37d2-4542-8e03-50b3d408ff42",
+    platforms=["linux"],
+    endpoint=[
+        {
+            "rule_name": "Linux Powershell Egress Network Connection",
+            "rule_id": "1471cf36-7e5c-47cc-bf39-2234df0e676a",
+        },
+    ],
+    techniques=["T1203"],
+)
+
+
+@common.requires_os(*metadata.platforms)
+def main() -> None:
+    parent_process_path = "/tmp/pwsh"
+    child_script_path = "/tmp/sh"
+    network_command = "exec 3<>/dev/tcp/8.8.8.8/53"
+
+    # Create the fake parent process script
+    with open(parent_process_path, "w") as parent_script:
+        parent_script.write("#!/bin/bash\n")
+        parent_script.write(f"{child_script_path}\n")
+
+    # Create the child script that will make the network connection
+    with open(child_script_path, "w") as child_script:
+        child_script.write("#!/bin/bash\n")
+        child_script.write(f"{network_command}\n")
+
+    # Make the scripts executable
+    common.execute(['chmod', '+x', parent_process_path])
+    common.execute(['chmod', '+x', child_script_path])
+
+    # Execute the parent process script
+    common.log("Executing the fake parent process script")
+    subprocess.Popen([parent_process_path])
+
+    # Allow some time for the network connection to be attempted
+    time.sleep(5)
+    common.log("RTA execution completed.")
+
+    # Cleanup
+    common.remove_file(parent_process_path)
+    common.remove_file(child_script_path)
+
+
+if __name__ == "__main__":
+    sys.exit(main())