From a security point of view, the new IPv6 protocol stack represents a considerable advance in relation to the old IPv4 stack. However, despite its innumerable virtues, IPv6 is still vulnerable.
Dual Stack Attacks
Though, the Internet is mostly IPv4-based, the adoption of IPv6 as the Internet protocol will increase. During the lengthy transitioning process, ‘6 to 4’ stacks will take care of this, by implementing IPv6 and IPv4 separately, or in a hybrid manner, which allows applications to work transparently over both IPv4 and IPv6. However, a dual stack transition deals with two non-interoperable protocols and their specific sets of security issues. This leads to more technical complexity, which will make configuration even harder and more prone to failure.
The modification of a source IP address, as well as the ports on which they are communicating, can be done to make it appear as if traffic originated somewhere else. There are best practice methods for filtering, as in RFC 2827, but this isn’t mandatory, which means many ISPs won’t implement it. The use of strong cryptography can thwart these attacks. On the other hand, even though IPSec support is mandatory on IPv6 (whereas it was optional for IPv4) it’s likely to experience the same hurdles as with IPv4 and not be widely deployed.
Flooding attacksDue to IPv6’s massive address space, it would take years to scan a single IPv6 block, versus seconds for an IPv4 block. Due to multicast traffic, which allows the user to send a packet to multiple destinations with a single send operation, distributed denial of service (DDoS) attacks, like Smurf, are possible.
With a Smurf attack (a type of broadcast amplification attack), a victim’s IP address is used to send an echo-request message with subnet broadcast’s destination address, along with a spoofed source address, causing all of the subnet’s end hosts to respond to the spoofed source address and flood the victim with echo-reply messages.
Header manipulation and fragmentation
Attacks exploiting header manipulation and fragmentation can do everything from bypassing intrusion detection systems (IDS), intrusion prevention systems (IPS) and firewalls, by using out-of-order fragments, or even go after the network’s infrastructure itself. Also, in IPv6, there are extension headers, which can be used to get around access control lists (ACL) on routers and firewalls, by causing devices at the end host to process router headers and forward them elsewhere.