Closing the Online Crime Attribution Gap: European law enforcement tackles Carrier-Grade NAT (CGN) | Europol:
"CGN technologies are used by ISPs to share one single IP address among multiple subscribers at the same time. As the number of subscribers sharing a single IP has increased in recent years –in some cases several thousand – it has become technically impossible for ISPs to comply with legal orders to identify individual subscribers. In most EU countries, when served with a legal order, these providers have a legal obligation to provide subscriber information on a person suspected of involvement in criminal activities.
The impact of this technological development on police work is considerable. An increasing proportion of investigations into terrorism and serious crime rely on the ability to identify offenders via a capability that is now being seriously eroded.
CGN technologies have been used by ISPs for a number of years as a solution to postpone the necessary financial investments to upgrade their networks to allow for the transition to the next generation of Internet Protocol Address version 6, or IPv6, which offers an unlimited pool of IP addresses. Due to the undeniable benefits of IPv6 over IPv4, this transition to IPv6 is called upon by the vast majority of internet engineering experts, governments, international organisations (including the UN and the EU), but also NGOs promoting a safe, open and secure internet." 'via Blog this'