Add windows checks

network/secure_your_own_device.markdown

@@ -28,7 +28,17 @@ More detailed recommendations can be found on [itsecurity.ethz.ch](itsecurity.et
 Windows
 -------
 
-- todo
+### Network and firewall
+
+Check that your network settings are set to **Public**.
+Go to **Settings** > **Network & Internet** > **Status** > **Network status**,
+go to the network interface **Properties** and set it to **Public**.
+This will automatically enable the firewall.
+
+### Windows Security
+
+Go to **Settings** > **Update & Security** > **Windows Security** > **Open Windows Security**,
+check that all is green.
 
 Linux
 -----