That’s why Moshe, 40, requested that his real name not be published. "We are playing with my kids’ lives," he told me.

Earlier this year, a forum of leading Haredi rabbis in Israel issued an injunction against using WhatsApp, which they described as "a great spiritual danger." A 2014 article in a Yiddish-language newspaper pointed to WhatsApp as the “number one cause of destruction of Jewish homes and businesses," citing rabbis who oversee divorces. Hasidic leaders have yet to fully ban the app, though they only allow it to be used with strong filters that block images and video. Those found to be using non-filtered phones could be ostracized from the community and have their children thrown out of ultra-Orthodox schools.

WhatsApp has become popular among the Haredi community — an umbrella term for ultra-Orthodox Jewish sects that include the Hasidim. For Moshe and other Hasidim, the app provides a window into the outside world, and a forum for candid debate and discussion. In their view, it’s a closed network that’s not explicitly connected to the open web. For Hasidic leaders, it’s the latest threat to centuries of tradition and insularity.

Moshe, like many other Hasidim, regularly skirts these rules with WhatsApp — the popular messaging application that Facebook acquired for $19 billion in 2014. On his second, unfiltered smartphone, he uses the app to share news articles and local gossip across several group chats, some of which include up to 100 members.

As a Hasidic Jew living in Brooklyn, Moshe’s online activities are extremely limited. His ultra-orthodox sect has long banned internet use, on the grounds that exposure to the secular world would lead to moral corruption, sexual promiscuity, and infidelity. The insular community has allowed for some exceptions, acknowledging that smartphones and computers are now essential for business, though its leadership still requires members to install web filters on their devices, blocking all social media services and all but a few whitelisted websites. Internet use among children remains strictly forbidden.

Like most people, Moshe spends a lot of his time messaging friends on his smartphone. Unlike most people, he can’t openly talk about it.

Hasidic leaders held a large anti-internet rally in New York in 2012.

Hasidic leadership has in recent years mounted a concerted campaign to control the web. In 2012, ultra-orthodox leaders held a massive anti-internet rally at Citi Field baseball stadium in New York, where they called for tighter restrictions on internet use. Ultra-orthodox rabbis have effectively limited outside media in the past, with edicts against television and radio, and tight controls over Yiddish-language newspapers. But the internet has proven more insidious, and with the rise of smartphones, it’s become even harder to control. Ysoscher Katz, a former ultra-orthodox rabbi, says the community’s insularity stems from the belief that strict adherence to tradition is the best way to preserve Jewish identity. "The idea is that once you adopt contemporary names, contemporary clothing, and contemporary language, then eventually that’ll lead to assimilation and dissolution of the Jewish community," says Katz, who grew up in the Hasidic sect but eventually left to become a rabbi and teacher at a more progressive orthodox community in New York. "They’re very worried and very afraid. And very anxious." He recalls Hasidic leaders "aggressively fighting back" when the internet began gaining traction more than a decade ago, with strict bans on household computers, and those efforts have only amplified as technology has evolved. "I would lie to you if I said I don’t sympathize with their concerns," Katz says. "They’re very worried and very afraid. And very anxious." So far, the community has policed smartphone use through a small group of approved filtering companies. Whitelisted sites and services are determined by local rabbinical boards, and the parameters can change from one community to another. But the guiding principle is that if it’s not business-related, it’s blocked. "The assumption is that any website could potentially lead to something inappropriate, or something dangerous or titillating," Katz says. "So the starting point is very low and the bar is very high."

(Mario Tama / Getty Images)

With WhatsApp, Haredi leaders face a new dilemma. At its core, the app is a messaging service, and ostensibly permissible for business use; but it also incorporates elements of social networks, which remain strictly forbidden. And with more community members, like Moshe, secretly carrying unfiltered phones and sharing links from the wider web, it’s become nearly impossible to keep the outside world at bay. Samuel Heilman, a professor of sociology at Queens College CUNY who has spent his career studying contemporary orthodox Jewish communities, describes Hasidic WhatsApp groups as vibrant forums where users share "everything from jokes to news accounts." He says that the group’s moderators are very "plugged in" to the news cycle. Last month, for example, Heilman first learned of the deadly stampede at Mecca through one of the group chats he was invited to join. "A real threat for their insularity." "There’s nothing now of the outside world that doesn’t find its way into these Haredi enclaves," he says. "And so this represents a real threat for their insularity." Last week, Moshe added me to a few of the dozen WhatsApp groups he created. One is devoted to business (he works in marketing and finance), and another for a small group of his close friends. The largest, and most active group, is primarily for general news and discussion. It includes around 100 members, though Moshe estimates that he personally knows around 30. Much of the discussion last week focused on the latest developments in Israel, and the escalating violence there, though group members shared links and media about other stories, as well — everything from the presidential primary race to local news. The conversation would shift between Yiddish and English, and at times, it was difficult to keep up. One minute, I would be scrolling through photos of Jimmy Kimmel shooting a segment in their neighborhood, or videos of young Hasidic men dancing at a recent event. Seconds later came videos of a bus that had caught fire near LaGuardia Airport, or news that a New York police officer had been gunned down. "I show him the middle finger, that I still have an opinion. He cannot censor my opinion." There was plenty of debate, and things sometimes got heated. But Moshe says that’s exactly the kind of dialogue that’s too often stifled by censored Yiddish media. He sees himself as a kind of editor for the group, dropping in links to spark discussions that wouldn’t happen in public. For him, it’s a quiet form of rebellion. "What is a filter? A filter censors you," he told me last week. "He wants to censor my mind. And I show him the middle finger, that I still have an opinion. He cannot censor my opinion."

(Ullstein Bild / Getty Images)