Preventing terrorist plots is harder than ever. And technology is both the problem and the solution.

Violent extremists like ISIS meet in the open on Facebook or Twitter. Then they take the conversation private, using technology called encryption to encode their messages.

It's called "going dark." And it's one of the most alarming concerns facing police and counter-terrorism officials worldwide right now. They worry they can't prevent the next terrorist attack -- an anxiety stoked in a big way by the November 13 attacks on Paris that claimed 130 lives.

"It's clear that our terrorist adversaries have figured out and learned what kinds of communication we've been in the past able to intercept. And they now understand that if they ... find other ways to communicate that they can shield their communications from us," National Counterterrorism Center Director Nicholas Rasmussen told CNN's Jim Sciutto in the CNN Special Report, "Targeting Terror: Inside the Intelligence War," which airs Tuesday at 9 p.m. ET.

What technology is ISIS using?

ISIS has a technology resource for jihadists looking to better cover their tracks. The terror group has five to six members offering 24-hour support on how to encrypt communications, hide personal details and use apps like Twitter while avoiding surveillance.

When ISIS terrorists want to hide what they're saying, they are increasingly turning to an app called Telegram.

The Berlin-based startup boasts two layers of encryption and claims to be "faster and more secure" than its competitor WhatsApp, which is owned by Facebook.

Last week, Telegram said it had blocked 164 ISIS-related channels across 12 languages.

But the blocking only impacts public channels. Private communications on Telegram are still protected. Users can securely message friends and send pictures and files. They can also create group chats with up to 200 members or opt for "special secret chats" where messages, photos, and videos will self-destruct.

Thanks to your reports, today we were able to block another 164 public channels used to spread terrorist propaganda. https://t.co/i0My3D4Nxa — Telegram Messenger (@telegram) November 19, 2015

What is the government doing?

FBI Director James Comey has repeatedly said that the use of social media by ISIS is unprecedented in terms of how aggressively it engages with people in the West. The "court orders" that law enforcement officials use to prevent crimes "are ineffective because devices are protected by encryption," Comey said last week.

Members of ISIS are essentially overwhelming the system, according to terror analyst Michael S. Smith II.

In the U.S., at least 52 Americans have been charged with terror-related crimes for allegedly supporting ISIS, according to public records. Intense surveillance by FBI plays a significant role.

Still, the problem is akin to finding a needle in a haystack. And there are a daunting number of haystacks, said Matthew Green, who teaches cryptography and computer security at Johns Hopkins University.

"Nobody can afford to read every email. There's too much communication for us to listen to it all, even if none of it is encrypted," Green said.

But government efforts to undermine encryption also raise broader concerns about privacy. They would lower the defenses used to keep confidential email, business plans, banking and much more.

How non-government groups are involved in the fight

Enter groups like Ghost Security.

The group differentiates itself from the vast and often disjointed hacktivist collective Anonymous, which has also declared war on ISIS and claims to have taken down pro-ISIS Twitter accounts. A handful of members were previously part of Anonymous, including one of the leaders, who goes by the name "DigitaShadow."

DigitaShadow says Ghost Security has taken down 149 Islamic State propaganda sites, 110,000 social media accounts, and over 6,000 propaganda videos since it formed. Following the most recent attacks in Paris, the crew is trying to gather intel on the attackers' digital footprints and identify social media accounts involved in the attacks. (CNN could not independently confirm this information.)

Ghost Security claims to have created automated software that identifies ISIS social media accounts. DigitaShadow says the collective has also infiltrated private ISIS communications, taken over ISIS social media accounts and pulled IP information to help identify and locate ISIS members. Ghost Security is primarily focused on bringing down ISIS, but they also target other Islamic extremists.