Step 1. Change to root user

In your terminal change to root user:

sudo su

Step 2. Turn of red/green led

To turn off the red led:

echo 0 > /sys/class/leds/led0/brightness

To turn off the green led:

echo 0 > /sys/class/leds/led1/brightness

Step 3. Stealth mode

Your raspberry pi is now in incognito!!

*Leds will turn back on after reboot