How Phreaking Works

[chushpan]

Phreaking is the practice of hacking into telephone systems, networks, and equipment to gain unauthorized access to communications services, make free calls, tap lines, or for other purposes. Historically associated with enthusiast experiments, the activity is now considered illegal and can result in criminal prosecution. Below are the basic principles of phreaking for educational purposes.

1. Historical Phreaking Methods​

Phreaking originated in the 1960s–1980s, when telephone networks were analog and vulnerable. Here are the key techniques:

A. Tone Phreaking​

• The gist: Early telephone systems used DTMF (digital tone multi-frequency) signals to dial a number. Some hackers, like the legendary John Draper ("Captain Crunch"), discovered that a cereal box whistle could produce a 2600 Hz tone, which was used by phone companies to signal a free line.
• How it worked:
  1. The hacker dialed the number using a regular telephone.
  2. Once connected, he would emit a 2600Hz tone to trick the system into putting the line on hold.
  3. It would then send additional tones to dial another number to make free calls.

B. Blue Boxing​

• The gist: Devices generating DTMF signals made it possible to simulate internal commands of the telephone network.
• Example: Hackers used Blue Box to dial numbers over long distance lines, hiding their actions.

C. Line Monitoring​

• The gist: In analog systems, hackers could connect to lines through physical access to wires or use "cross-connects" (switches on the PBX) to listen in on conversations.

2. Modern Phreaking Methods​

With the transition to digital and VoIP networks, phreaking has become more difficult, but is still possible through:

A. SIP engineering (VoIP attacks)​

• The gist: SIP (Session Initiation Protocol) manages VoIP calls. Hackers can:
  • Intercept SIP sessions through MITM attacks.
  • Use tools like SIPVicious to scan for vulnerable servers.
  • Disguise calls as legitimate (spoofing) using fake SIP headers.

B. SIM Swapping​

• The gist: A hacker convinces a mobile operator to transfer the victim's phone number to their SIM card. This allows them to receive two-factor authentication SMS codes and make calls on behalf of the victim.

C. Voice Phishing (Vishing)​

• The gist: A combination of phishing and phone calls. The hacker calls the victim, posing as a bank or support service employee, and tricks them into giving up confidential data.

D. Hardware manipulations​

• The gist: Using devices like Raspberry Pi or specialized GSM modems to create illegal base stations (e.g. IMSI catchers) that intercept mobile traffic.

3. Main vulnerabilities used in phreaking​

Vulnerability	Description	Protection
Weak authentication	No call authentication.	Using two-factor authentication (e.g. hardware tokens).
Open SIP servers	Unsecured VoIP servers.	Setting up firewalls, RTP/SIP encryption.
Human factor	Trust in the caller.	User training (security awareness).
Physical access	Connecting to wires.	Controlling access to infrastructure.

4. Legislative and ethical aspects​

• Illegality: Phreaking violates laws in many countries, including those against fraud, unauthorized access to information, and wiretapping.
• Consequences:
  • Fines and imprisonment (for example, in the USA - Computer Fraud and Abuse Act).
  • Account blocking and legal action from victims.
• Ethical approach: Study telecommunications security through certifications (such as Certified Telecommunications Network Specialist ) or CTF platforms.

5. How to protect yourself from phreaking?​

1. Use secure VoIP services (e.g. with SRTP encryption).
2. Enable two-factor authentication (preferably through apps like Google Authenticator rather than SMS).
3. Update your equipment (routers, IP phones) to eliminate vulnerabilities.
4. Monitor traffic for suspicious activity (eg unexpected international calls).
5. Train employees to recognize vishing attacks.

6. Educational resources​

If you want to study Telecommunications Security legally:

• Books: "Hacking Exposed VoIP" (John Herlich), "Telecom Security" (Daniel Benedict).
• Platforms: TryHackMe (VoIP security courses), Hack The Box.
• Certifications:
  • Certified Ethical Hacker (CEH) - includes network auditing.
  • Cisco CCNA/CCNP Security - Telecommunication Network Security.

Summary​

Phreaking is a complex field that requires knowledge of telecommunications, programming, and social engineering. However, it is important to remember: any attack on systems without permission is a crime. Instead, focus on ethical hacking and securing infrastructure. If you are interested in practical examples or code for learning, let me know!

 

[Man]

History and modernity of phreaking​

Phreaking is the practice of hacking telephone networks to make free calls, manipulate communication systems, and research telecommunications infrastructures .

How did it work before?​

In the era of analog telephone networks (1960–1990s), phreaking was based on the exploitation of signaling features:

1. Tone dialing (DTMF)
   • Telephone companies used tones (such as 2600 Hz) to control connections.
   • Phreaks would imitate these tones using whistles (such as the famous Cap'n Crunch whistle ) to fool the telephone exchange and gain access to long-distance lines.
2. Blue Box / Red Box / other devices
   • The Blue Box generated control tones (2600Hz + MF signals) allowing calls to be routed.
   • Red Box simulated coin signals in payphones for free calls.
3. Hacking operator systems
   • Some phreaks studied Bell System documentation, found backdoor passwords and gained access to service functions.

Modern Phreaking​

With the transition to digital networks (VoIP, SS7, 4G/5G), classic methods have become obsolete, but new vulnerabilities have appeared:

• Hacking VoIP services (SIP vulnerabilities, account selection).
• SS7 attacks are exploitation of vulnerabilities in the signaling protocol to intercept SMS and calls.
• SIM swapping is the transfer of the victim's number to your SIM card through social engineering.

Legality​

Phreaking s iillegal in most countries and punishable under fraud, hacking, and disruption of communications.

Want to learn more about specific methods or historical examples?