Yesterday, in my diary about the scans for "/proxy/" URLs, I noted how attackers are using IPv4-mapped IPv6 addresses to possibly obfuscate their attack. These addresses are defined in RFC 4038. These addresses are one of the many transition mechanisms used to retain some backward compatibility as IPv6 is deployed. Many modern applications use IPv6-only networking code. IPv4-mapped IPv6 addresses can be used to represent IPv4 addresses in these cases. IPv4-mapped IPv6 addresses are not used on the network, but instead, translated to IPv4 before a packet is sent.