The latest WikiLeaks revelations—purportedly revealing CIA hacking tools and techniques—are a reminder of just how vital cybersecurity is. A big area of concern … the so-called Dark Web, a largely hidden online world where some of the most serious crimes are committed.

The FBI has dedicated teams to battle cyber criminals, and one of its special agents agreed to give me an introduction to the Dark Web.

Here’s a transcript of my interview with FBI Special Agent Chris Christopherson:

Chris Christopherson/FBI Special Agent: We work the national security side and we work the criminal side.

Attkisson: FBI Special Agent Chris Christopherson agreed to show us how the Dark Web works, inside the FBI’s first Regional Computer Forensics Laboratory in San Diego.

Chris Christopherson: So if you think about this iceberg here, as content up on the internet, the Dark Web or the Deep Web represents everything that’s underneath that water level and then what we see on top of the water level is represented by content that Google sees. So, things that you can access through regular search engines, and then things that are underwater or on the Deep Web. So what we’re looking at here is a website where you can actually go ahead grab some software, this Tor browser, that would enable you to go on the Dark Web or the Deep Web. The idea of Tor is two parties; they don’t know the other party in the communication. They’re just communicating. So Google actually doesn’t know where to go, because everything is so anonymous, and the encryption it’s obfuscated, Google just simply can’t find it.

Attkisson: Like the Silk Road website.

Christopherson: Exactly. So Google if they could would index it, but at the end of the day if you don’t know where it is, you can’t find it and you can’t search it.

Attkisson: Silk Road was an online black market launched on the Dark Web in 2011, primarily to sell illegal drugs.

Christopherson: We put up a site and banner to notify the people on the forum on the marketplace, say, “Hey, we’re investigating these things. It is illegal, and these are crimes, and you’ll get punished for them.”

Attkisson: If someone visiting that site went to it and saw this, I’m sure they’d be a little concerned about criminal activity.

Christopherson: That’s what we’re hoping for. Yea, exactly, yea.

Attkisson: The FBI shut down Silk Road in 2013. Its operator, Ross Ulbricht, was convicted of money laundering, computer hacking, and drug trafficking.

Christopherson: The guy that ran Silk Road is sentenced to a long prison sentence, and so on. We’ve seen how the investigation has actually broken though some of those anonymity borders. Where at the end of the day, drugs have to get sold and delivered. So even though this is online and anonymous, there still has to be some component that’s real world and not anonymized. And that’s where the FBI and other law enforcement agencies can kind of come in and identify the actors on this forum and others.

Attkisson: Another crime found on the Dark Web involves cyberattackers who infect your computer with ransomware and encrypt your files and folders. You might not know it until you try to get data and see a computer message like this.

Christopherson: If you’re infected with this ransomware and you start to utilize your computer, open files, you’ll see this message. And what you can kind of see at the top is that the ransom itself is $500, and you have a countdown timer here, so once that countdown timer hits zero the ransom will double. So what they’re trying to do is to ensure that sort of time sensitivity so that you go through, and go through the difficult process of finding one of these exchangers, getting Bitcoins, and so on.

Attkisson: Bitcoin is a payment system a new kind of currency that’s anonymous, with no central authority. Cyber criminals holding information for ransom often demand payment on the Dark Web in bitcoin.

Christopherson: They’ll have their Bitcoin Wallet information on there. They’ll have information about how to pay the ransom. So this is something that they need to actually send out to all their victims anonymously. The internet with anonymous traffic is synonymous with the Dark Web. So the Dark Web is really conducive with this kind of criminal activity. There are local Bitcoins, as you see here, where I can actually meet face-to-face with someone in person, give them money, and get Bitcoins from them. And then there are ATMs, even here in San Diego, where you can get Bitcoins from the ATM. So you can either purchase Bitcoins in the ATM, or you can trade the Bitcoins in for money.

Attkisson: But do the crooks then exchange it for cash and spend it, or do they buy other illicit things with it?

Christopherson: So that’s a good question. “Can I buy groceries with Bitcoin?” And the answer is yes, you can in certain cities and places, you can buy Subway, you can buy martinis, you can buy groceries. But at the end of the day, they’re probably going to exchange it for cash. And so they can use these same exchangers to turn their Bitcoin into Euros, dollars, or whatever they’re looking for.

Attkisson: When people have their emails stolen, their email addresses and things like that from retail stores like we’ve heard of, is this what some of them are potentially used for?

Christopherson: Exactly. So there will be certain trading on the Dark Web of email address of victims. There’s also the potential that once someone pays a ransom once, their email address or some other identifier might be sold or traded on the dark web, and now they’ll be targeted again.

Attkisson: To help protect against ransomware attacks, the FBI recommends backing up your data regularly and making sure they’re not connected to the computers and networks that they’re backing up.