Intrusion Detection FAQ: Can I use the MAC address of an Ethernet packet to trace an attacker?
If the attack originated from a system that has a direct connection to your system with no gateway in between, then you can use the MAC address. But, if a gateway is in the path, then the gateway replaces the MAC address of the sender with its own address. As a result, you can trace the attack to the gateway only. If the gateway has extensive logging enabled, you might consider searching the log file for more information.
Dirk Lehmann
Siemens CERT
504 was a great course to better enhance my understanding of attack methods and how to better defend my systems
-Dustin Odsa, Indiana University