Just a thought, but if someone Pinged me and I was somehow able to reply, but with an altered IP address...what would happen?
Assuming we are talking about hackers. They would probably next run a traceroute which would lead them to hacking someone else probably Jimbob
Probably one of two things... Either by sending any reply back at all, you've simply confirmed that your system is there. (For example, I send out a single ping aimed at your IP address, if I get a reply back, regardless of what's in that reply, I know "something" replied to my ping. Since I only sent one ping packet out and it was aimed at you, then that reply must be from you, no?) Or the another possibility is that since you altered the reply packet, you've corrupted it as far as what my system expects to get back from a valid echo request reply. Therefore my system views that incoming packet as either invalid or unsolicited, drops it, and from my perspective I got no reply at all to my ping. Frankly, I don't know the technology at the necessary level to know what exactly would happen if you doctored the contents of the reply packet, but I do know it isn't going to fool the person into forgetting that they originally pinged IP address 1.1.1.1, just because the the reply packet says "hi, IP address 2.2.2.2 is here."