Ping is a standard (and very useful) internet troubleshooting tool, used to indicate that a device is powered and connected. When a ICMP packet is received, the device sends an ICMP reply – similar to a sonar ‘ping’ bouncing off a submarine. ICMP packets are very small, so they place negligible overhead on the internet infrastructure.
However a ping reply can signify to a hacker that there is a device or LAN which deserves closer attention. By stopping your router from replying to the ping (and any other unsolicited message), you encourage any passing hacker to think that there is no device connected at your address.
From your Vigor router’s web configurator Main Menu, select System Maintenance >> Management. In the top left of the management Setup page, in the Management Access Control section is a tick-box with caption “Disable PING from the Internet”. If you tick this box, the router will NOT respond to pings from the internet.