Hacking the phones: The phone phreaks

Image of someone dialing a rotary phone - Destination Certification

It was a different world. A world where FaceTime, Slack and Discord were mere science fiction. If you wanted to communicate across the country or across the world, you had to pay heavy fees to the phone companies.

Many of the early participants were teenagers and college students. Often having moved across the country for their studies, communicating back home was a challenge. Letters took time, and these young people didn’t have the money for regular calls. But they did have a lot of spare time, curiosity, and a will to commit mischief. They were the phone phreaks.

The origin story

The godfather of it all is an interesting man named Josef Engressia Jr.. He was born blind, but made up for it with other abilities. He had perfect pitch and claimed an IQ of 172. Without vision, it’s no surprise that he gravitated to the audio world. From an early age he became obsessed with the telephone, and by seven years old, he had figured out that he could make calls without using the rotary dial to enter the numbers.

Hook switching

Instead, Josef used the hook switch. It’s a little hard to tell from the picture above, but a hook switch is a little button that is depressed when the handset is resting in its holder. To dial a 1, he would press it a single time, then pause for a moment before entering the next number. Dialing a 2 involved two quick taps then a pause. A 3 required three taps, and so on, until a 9, which was nine taps. A 0 required ten taps.

So if he wanted to dial 911, he would tap nine times, then one time, then once again. This process, known as switch hooking, made it possible to place calls from phones even if they have the rotary dial or keypad disabled by a keylock.

2600 hertz: The magic tone

For his next trick, Josef’s perfect pitch came in handy. By whistling at a pitch of 2600 hertz, he could reset the line. He would then produce repeated short whistles at this tone using the pattern we described above. This allowed him to dial numbers, giving him free calls.

Through both Josef spreading the word and other phone phreaks figuring out how phone systems work, a burgeoning phone phreak culture was born. Not everyone was capable of whistling at precisely 2600 hertz, but nothing stays in the way of motivated teens for long.

Serendipitously, a breakfast cereal toy held that exact same frequency. Cap’n Crunch came with a whistle that was the savior for many of the early phone phreaks. All they had to do was blow it in short bursts and they could reset the line, then dial away. With the Cap’n Crunch whistle, they could call their friends and family back home or menace the phone lines with prank calls.

Blue boxes

As time progressed, the phone phreaks got more sophisticated. They began to develop tools known as blue boxes to make it easier to get free calls. These boxes could produce the right tones at the press of a button, sending out the correct 2600hz bursts for each digit they wanted to dial.

The predecessor to Apple?

In the early 1970s, Steve Jobs and Steve Wozniak came together to build a blue box that would make the necessary tones for free long distance calls. This was one of the first electronics projects that they sold together, and in the foreword to the book about phreaking, Exploding the Phone, Wozniak states that both he and Jobs believe Apple wouldn’t have existed without their blue box.

Black boxes

Black boxes were another important tool in the phone phreak toolbox. They were small circuits that could be attached to someone’s home phone, allowing the user to receive incoming calls without the caller having to pay.

Red boxes

The emergence of hacking culture

These electronic devices emit a tone that tricks payphones into thinking that coins have been deposited. With a red box, phone phreaks could get free calls from payphones whenever they wanted.

Voice mail boxes

One of the pillars of the phone phreak community were voice mail boxes. The phreaks would probe through the phone network to find an unused voice mail box, then spread the word. Phone phreaks could then communicate to one another by calling these voice mail boxes and leaving messages. They would use them as communication hubs, leaving messages for one another until the owner of the mailbox discovered the abuse.

The emergence of hacking culture

The phone phreaks were hackers. They came across systems, explored them, poked around, and found ways to subvert them. Many of them just did it for fun, lots were in it for the free calls, some were in it for pranks, community or as a hobby. But fundamentally it was about finding holes in the systems. Many of the early phone phreaks extended their hobby across computer networks as technology developed, so they played a crucial role in the emergence of hacking culture.

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Cybersecurity and privacy writer.

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