After Facebook and web hosts recently began banning white nationalist content, neo-Nazi extremist groups are urging members to meet offline and to use encrypted networks, Motherboard has learned.

The strategy mimics ISIS efforts as it faced a crackdown on its content by major online platforms in 2015, during the height of a migration into its ranks by western followers. At the time, a spate of ISIS attacks in Europe exposed how the terror group planned operations and recruited using social media networks, leading Silicon Valley giants like Google, Facebook, Twitter, and Microsoft to ban ISIS content.

In response, ISIS members retreated to encrypted apps like Telegram and disseminated a counter-surveillance tool kit, in which they advised members to specifically use ProtonMail—a Swiss email provider that says it’s immune to spying from sophisticated intelligence agencies. (After the ISIS attack at the Bataclan in Paris, ProtonMail came under fire because its service was listed as being preferred by ISIS.)

Similarly, neo-Nazi extremist groups have, in recent weeks, begun advising their members to use the email provider to evade authorities and maintain reliable lines of communication to potential recruits.

One group illustrating the online evolution of right wing terror groups is a burgeoning extremist network called the Feuerkrieg Division (FKD), which is listed by several terrorism trackers, including the TRAC analysis consortium and the not-for-profit Counter Extremism Project (CEP).

Originating in Europe and taking direct inspiration from the American hate group Atomwaffen Division (AWD), FKD bills itself as a “paramilitary organization.” In the aftermath of the Christchurch attack in New Zealand, it has encouraged its members to commit terrorism and “take action.”

“The Feuerkrieg Division (FKD) is a Revolutionary National Socialist underground paramilitary organization,” reads an FKD message posted online, before encouraging potential members to join and contact its ProtonMail address.

The group’s official active Gab account, which advertises its encrypted contact address, recently displayed a picture of a copy of Siege—a neo-Nazi insurgency bible—and a pistol, along with a graphic image calling for the assassination of a Belgian politician.

Motherboard tracked how the group funnels potential recruits from its Gab account to its ProtonMail address. It also appeared to recruit an American based in New Jersey (who is particularly active in calling for shootings and bombings stateside) via Twitter and claims a number of American members.

In another exchange on Gab, a popular online neo-Nazi with links to another militant organization asks the FKD Gab account how to contact them. The account replies: “Send us a message on our protonmail account, we will continue from there.”

A YouTube comment by an online supporter and suspected member of FKD says he's using mainstream social media sites as a first step in making contact with recruits to then “safely” network an IRL cell.

“Most members are scattered all over the western nations so we need some propaganda for recruitment first, then we can safely go off the grid knowing that at least each cell has more than one member ,” he wrote under a video warning of upcoming terror attacks by the group with the ominous title “Soon”.

Motherboard saw FKD and its related member accounts having connections to other far-right militant groups and AWD.

Among the FKD’s extensive propaganda trove is a video flagged by journalist Jake Hanrahan, showing homemade bombs exploding in a forest. Several of its videos on YouTube call for upcoming terror attacks and atrocities, but haven’t been taken down by the streaming giant.

FKD is linked online to other far-right extremist groups undertaking similar operational security measures. Motherboard has observed other neo-Nazi organizations using and promoting their ProtonMail accounts, while at least one militant network was using an encrypted chat app to convene more covertly and plan IRL activities.

When contacted by Motherboard, a spokesperson for ProtonMail said the company was “deeply concerned” that FKD and other groups were using its email services.

“We're quite surprised to find that white supremacist groups are favoring ProtonMail given our very vocal position on diversity in tech, and our past blocking of accounts which are inciting violence,” they said, adding that the company thoroughly investigates any accounts accused of hate speech or promoting violence.

“We believe privacy is a human right, and encryption and anonymity are powerful safeguards for dissidents, whistleblowers, and journalists. However, we also have a zero-tolerance policy toward illegal activity of any kind. This includes discriminatory hate speech, which is illegal in Switzerland,” the company said.

Many far-right extremist groups operate completely unabated on Gab, a social media platform that considers itself a free speech champion and is widely used by neo-Nazis. These groups use Gab as a gathering point for contact with potential recruits in much the same way jihadist organizations once used Twitter as their chief recruitment point.

ProtonMail email accounts are advertised by militant groups on their Gab profiles; in 2014, ISIS used Twitter accounts connected to Kik messenger profiles to advertise to followers looking to contact a recruiter directly.

The CEP which keeps a close eye on far-right terrorism, has noticed the power of Gab among rightwing extremists.

“Using Gab as an introductory platform before going to secure email is one example of the danger of allowing extremist groups to widely use a platform unencumbered,” said CEP researcher Joshua Fisher-Birch, “especially when it comes to groups that have violent intentions, like the Feuerkrieg Division.”

These developments come at a time when Congress is holding hearings about the veracity of the neo-Nazi and white nationalist terror threat in America.

“We definitely saw jihadist groups of all stripes, but mostly ISIS, respond to being kicked off social media platforms by retreating to Telegram,” said Amarnath Amarasingam, a terrorism expert and senior research fellow at the Institute for Strategic Dialogue, who carefully tracked the rise of ISIS online.

“The downside of this was that they became harder to watch and harder to track, but the upside of course is that they sat together in a little bubble and talked amongst themselves,” he said. “They were talking to people who were already radicalized to some extent, and had a harder time reaching new audiences. The same thing is likely to happen to far-right groups.”

Yet Amarasingam maintains that the difference falls in the IRL space, where ISIS supporters were heavily surveilled by intelligence and law enforcement agencies that took the threat seriously. When it comes to the far-right, authorities haven’t properly taken the threat of terrorism seriously, even in the face of ongoing attacks by white nationalists around the world.