The transition from a pure IPv4 network to a network where IPv4 and IPv6 coexist brings a number of extra security considerations that need to be taken into account when deploying IPv6 and operating the dual-protocol network and the associated transition mechanisms. This document attempts to give an overview of the various issues grouped into three categories:</t><t> o issues due to the IPv6 protocol itself, o issues due to transition mechanisms, and o issues due to IPv6 deployment.</t><t> This memo provides information for the Internet community.