TV and film streaming service Netflix has announced that it intends to actively prevent users from using virtual private networks (VPN) to hide their geographic locations in order to gain access to content that is not available to their locale, since Netflix is now available in 190 countries.

"Some members use proxies or 'unblockers' to access titles available outside their territory. To address this, we employ the same or similar measures other firms do. This technology continues to evolve and we are evolving with it," David Fullagar, Netflix's VP of content-delivery architecture, wrote in a blog post on 14 January.

"That means in coming weeks, those using proxies and unblockers will only be able to access the service in the country where they currently are. We are confident this change won't impact members not using proxies."

VPNs are services that allow users anywhere in the world to connect to a private network on the internet. There are some free VPN services, but they either do not offer a lot of bandwidth or might be connected to botnets, such as Hola.

Another solution is to use a DNS unblocker service, whereby you pay a service and then change your Domain Name System (DNS) address settings on your computer or device to point at the unblocker's servers, which then routes your internet traffic through a US proxy so it looks like you are located in the US.

Blocking VPNs and DNS unblockers could cost everybody a lot of money

Obviously not every single person signed up to a VPN is using it to try to cheat Netflix, but a great number of people in tech-savvy countries do use it for this purpose.

They learn about Netflix and budget for the cost of a good, secure VPN with a good reputation, then they sign up for Netflix US, and as far as they're concerned, they have invested in a service they want to use, and that's that.

So if Netflix makes good on its threat to block VPNs, Netflix stands to lose out, as many of these people could easily just cancel their subscription and move to another service that is willing to turn a blind eye to VPNs or doesn't care about DNS unblocking. This means the content providers will also lose money, and the VPN providers and DNS unblockers could easily lose customers too.

"I'm willing to pay for solutions – but if they push me back to torrenting my content, I think it's a very sad direction. Many are willing to pay for the content, but are unable to," said Reddit user bICEmeister on a recent thread complaining about the news.

Fellow user belgarionx2 added: "I live in Turkey. We recently got Netflix here and it has 10% of the US content. I was paying happily for Netflix (US) and also for VPN. If they block this; I'll start pirating. No one cares about piracy here any way, I was paying because I just wanted to."

But how would you go actually about blocking location cheaters?

However, although Netflix says they want to prevent users from tricking it into thinking that foreign users are based in the US, which has much more content available than other countries thanks to favourable licensing agreements, the service admits that it is not all that easy to block VPNs. How would they go about doing it?

1) Blacklist popular VPN providers known to be used by many people

One way to stop people from hiding their geographic location would be to put the most popular VPN providers on a blacklist and block any connections from these providers. However, even Netflix admits that it is possible to get around this:

"We do apply industry standard technologies to limit the use of proxies. Since the goal of the proxy guys is to hide the source it's not obvious how to make that work well. It's likely to always be a cat-and-mouse game," Netflix chief product officer Neil Hunt told The Globe and Mail on 10 January.

"[We] continue to rely on blacklists of VPN exit points maintained by companies that make it their job. Once [VPN providers] are on the blacklist, it's trivial for them to move to a new IP address and evade."

2) Block all connections that seem to come from the same IP address

If many users all seem to connect to Netflix US from the same IP address, then it's a dead ringer that they are using a VPN. Even if Netflix doesn't know about that particular VPN yet, they can then choose to add this VPN to their blacklist.

3) Blacklist DNS unblocker services

DNS unblockers are easier to block than VPNs. In theory, it would be possible for Netflix to double-check what your actual IP address is by quietly getting your device to ping an external domain, and then send the IP address from the external domain to Netflix's servers. If the IP address appeared to be different, then Netflix would know that you were trying to cheat and could block the DNS unblocker's servers.

3) Take a leaf from Steam and iTunes' book and restrict users to their billing country

Another method Netflix could use to make sure users are definitely not cheating the service by hiding their locations is to restrict the user to only using the service in the same country as their billing information is registered to.

So if you're in the UK and you use a UK bank/credit card to pay for your US Netflix subscription, Netflix would know that you definitely don't live in the US. However, there are still ways around this – in theory you could subscribe to a service offering a US forwarding address, and then apply for a prepaid virtual credit card using that address, which is what a lot of people do when they want to shop on US websites that don't offer international shipping.