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The organisation responsible for allocating new IP addresses across in Europe, the Middle East and parts of central Asia says it has finally run out of IPv4 addresses.

IPv4 addresses are the 32-bit numbers used to identify devices on the internet. There are only 4.2 billion IPv4 addresses in existence and the rapid growth in the number of devices -- everything from smartphones to PCs to TVs or Internet of Things sensors -- has rapidly eaten through the supply.

"We have now run out of IPv4 addresses," said The RIPE Network Coordination Centre (RIPE NCC) in Amsterdam, which allocates IP addresses across 76 countries to ISPs and other organisations.

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The news is not a total surprise; rather, it has been expected since 2012 when RIPE NCC got its final allocation of IP addresses from the Internet Assigned Numbers Authority (IANA).

However, as the only source of 'new' IPv4 addresses in the region, the RIPE NCC said its announcement would increase pressure on network operators and raises concerns over scalable internet growth.

Any IPv4 addresses returned to RIPE NCC from now on, such as from organisations that have gone out of business, or from networks that return addresses they no longer need, will be allocated via a waiting list. This is expected to account for a few hundred thousand per year. "Nowhere near the many millions required by networks today," RIPE NCC said.

Despite warnings, the successor to IPv4 -- IPv6 – has still not been widely adopted, and much of the internet today still runs on older IPv4 networks, which means operators may be required to use complex and expensive workarounds or to adopt IPv6, RIPE NCC said.

Nikolas Pediaditis, Registration Services and Policy Development Manager at RIPE NCC, said: "With IPv4 exhaustion, we risk heading into a future where the growth of our internet is unnecessarily limited -- not by a lack of skilled network engineers, technical equipment, or investment -- but by a shortage of unique network identifiers."

In recent years, this scarcity has fuelled a substantial secondary market in used IPv4 addresses, with prices ranging from 10-30 euros per address, meaning the IPv4 transfer market is now worth hundreds of millions of dollars globally.