Netflix may be winning the war on cross-border watchers, but some of its targets refuse to go down without a fight.

The global streaming giant launched its crackdown on border hoppers in mid-January. Ever since, unblocking services have been struggling to evade it.

Unblockers provide Netflix subscribers with the technology needed to watch shows restricted to other countries.

Earlier this week, CBC News ran a story about unblocking companies that appear to have given up the Netflix fight.

But some others are still refusing to concede and are finding ways around the Netflix blocks, says the tech security and privacy advice website Comparitech.

Comparitech writer Paul Bischoff has been tracking the action since the border battle began. He told CBC News his theory on how Netflix has crushed so many unblocking companies and why a handful are still standing — for now.

Netflix tracks you

Bischoff first noticed something was up a few months after Netflix started its crackdown.

He uses various unblocking services that provide a VPN — virtual private network — that hides his location so he can watch Netflix shows in other countries.

"I couldn't connect to Netflix over the VPN anymore and get all the shows."

This is the message many Netflix customers see when they try to watch shows restricted to other countries. (Allana Mayer)

Bischoff was in Bogota, Colombia, at the time and now resides in Germany. He says both countries have poor Netflix offerings compared with its U.S. library, where he prefers to access content.

Bischoff checked out about 25 unblocking companies and discovered the problem was widespread. "Some said we don't support Netflix unblocking anymore or we're temporarily blocked. And then they end up being permanently blocked."

So how does Netflix know where to attack? Bischoff says that every computer device connected to the internet has an IP or internet protocol address where the streaming service can identify your location.

Tech writer Paul Bischoff in Germany says a handful of VPN providers are refusing to give in to Netflix's war on cross-border watchers. (Paul Bischoff)

When a Netflix subscriber uses a VPN, it can trick the company into thinking the subscriber is in a different country — say the U.S.

The problem, Bischoff says, is that many VPN services provide numerous customers with exactly the same foreign IP address. That's a red flag for Netflix, because normally a single address is connected to only one device.

"Bigger VPN companies can have even thousands of people connected to one IP address, so they're much easier to spot," says Bischoff.

"[Netflix] can go in and identify it and then put up a firewall to blacklist that IP address from connecting."

Bischoff believes Netflix may also be using technology to identify how people connect to its service.

"Whenever you connect via a VPN," he says, "there may be some metadata, some extra information attached. They can spot that extra information. And then they block it."

Winners and losers

Bischoff says several unblockers appear to no longer offer foreign Netflix access. His list of casualties includes Toronto's Unotelly; Barbados' Unblock-Us; Australia's uFlix; and Denmark's Unlocator.

But Bischoff says he's found a handful of major VPN providers still managing in some fashion to bypass Netflix's blocks. They are: ExpressVPN in the British Virgin Islands, Buffered in Hungary, StrongVPN in the U.S., VyperVPN in Switzerland and NordVPN in Panama.

Bischoff says he believes some VPN providers are circumventing Netflix blocks by constantly switching customers to a different host server so their IP address changes.

"Usually a VPN server will remain functional for accessing Netflix for about one to two months, I would say, and then they have to change."

Netflix may be going after customers who are sharing the same IP address, a sign that they may be using a VPN to watch shows restricted to other countries. (Elise Amendola/Associated Press)

Bischoff says the companies typically don't want to draw attention to what they're up to, so blocked customers often need to contact the VPN provider to find out which new server to connect to.

"They're not going to publicly post, 'These servers are working on Twitter today, these servers are bypassing Netflix.'"

Note that Comparitech receives a referral fee for many VPN providers it recommends that prompt customers to sign up. However, the company says it would never let referral fees colour its recommendations and has given negative reviews to providers offering such fees.

NordVPN dodges Netflix

Panama's NordVPN confirmed to CBC News that it's constantly switching its servers to throw Netflix off the trail.

"Ever since the initial VPN 'crackdown' began, NordVPN has continuously offered [a] Netflix workaround in some capacity and at least limited connectivity," said the company's CMO, Marty P. Kamden in an email.

Kamden told CBC News which of its servers are currently working for people who want to access U.S. Netflix, but asked that we not publish the information.

"It often changes, so if you publish these server numbers today, they might be different tomorrow. It is better to encourage your readers to consult with our tech support."

Bischoff concludes that the only unblocking companies surviving now are ones too small to register on Netflix's radar and those like NordVPN which have enough resources and cash to keep skirting the company's blocks.

The tech writer says he understands why Netflix started this war. He explains the streaming service must honour its country-exclusive licensing agreements with Hollywood studios.

With some VPN services still putting up a fight, Bischoff believes the only way to end the battle is to reform copyright rules.

"When everything is available everywhere, a regional copyright restriction or country-specific copyright restriction seems pretty antiquated," says Bischoff.

"But that's the way it works, and until we have something to replace it, Netflix is sort of handcuffed into doing this [crackdown].

Netflix did not respond to CBC News's request for comment.