“Telecommunications is like the bloodstream of business: it flows ceaselessly, connects everything, and operates unnoticed—until someone interferes.”
Today, it is natural for companies to use mobile phones, VoIP calls, SMS, or even networks of IoT devices on a daily basis. However, few consider that these telecommunications systems, upon which business operations fundamentally rely, have been the targets of hackers and fraudsters for over 180 years. Moreover, attacks against telecommunications never remain mere technological curiosities. The very first documented case, the manipulation of the French telegraph in 1834, led to serious financial fraud. Since then, attackers’ methods have continuously evolved, but the goal has remained the same: to obtain information or gain financial benefit from communication systems.
In this article, we will present the most important historical milestones of telecommunications hacking and explore the threats that companies face in the present day. We will also cover how Unicorn’s IT security, network management, and system integration services can help protect modern telecommunications channels.
1834: Hackers take the stage – The manipulation of the French optical telegraph
The history of modern hacking did not begin with the advent of computers. As early as the 1830s, there were those who recognized that the faster information flows, the greater the chance that someone will try to gain an unfair advantage through it. Every era of technological advancement has created new opportunities in communication, and with them, new risks. The first known telecommunications hack proved just that.
In France during this period, the state-operated optical telegraph network, known as the Chappe system, was in use. It was considered the pinnacle of communication technology at the time: the telegraphs transmitted coded signals from city to city via towers, using the position of mechanical arms. Information reached its destination much faster than by post.
This opportunity was exploited by the Blanc brothers, who bribed one of the tower operators to send them fresh stock market information using hidden signals. This allowed them to learn about market movements days before their competitors, enabling them to make significant financial gains. By the time the official news arrived, the Blanc brothers had already made advantageous deals based on the insider information. Although the fraud was discovered, no law existed under which the brothers could be convicted. Thus, this case became practically the first documented cyberattack and the first instance that prompted lawmakers to begin regulating the protection of telecommunications.
1903: The vulnerabilities of wireless communication
The dawn of radio was not free from attacks either. When Guglielmo Marconi introduced his new wireless telegraph, the world watched the technological breakthrough with amazement. One of the system’s great promises was that it would enable secret and uninterrupted communication, but it soon became clear that this was far from the truth.
A mischievous inventor, Nevil Maskelyne, decided to demonstrate its vulnerability using manual radio interference. During Marconi’s public demonstration, he began broadcasting a jamming signal on the demonstration’s frequency with his own radio transmitter, sending mocking messages to Marconi’s receiver. He spectacularly demonstrated that the technology advertised as “un-eavesdroppable” was actually easily vulnerable, and that wireless communication remained defenseless against malicious interference if security aspects were not treated as a priority.
This incident once again highlighted a fundamental truth that remains valid to this day: any new telecommunications channel must be protected against abuse, even if the technology is being presented as “revolutionary”. The same is true today for modern systems like 5G mobile networks or IoT (Internet of Things) devices. These pose serious business and security risks if we do not ensure their secure design, proper encryption, and continuous monitoring during implementation. That is why Unicorn’s experts pay special attention in every such project to incorporating the appropriate security controls from the design phase and ensuring the system’s continuous protection during operation.
The era of telephone networks and the phenomenon of phreaking
The mid-20th century opened a new chapter in the history of telecommunications hacking. So-called “phreakers,” curious and ingenious “tech enthusiasts,” discovered that the audio signals used to control telephone networks could be manipulated, allowing them to generate free long-distance calls.
The telephone systems of the time used audio-frequency signals to control calls, which were transmitted on the same voice channel as the conversations themselves. This meant that if someone could accurately replicate the correct control tones, they could manually influence call routing. The legendary 2600 Hz whistle—which phreakers discovered in a toy whistle found in a cereal box—produced the exact tone that telephone exchanges used to signal the disconnection of long-distance calls. By using the whistle, phreakers could “reopen” the line and then send their own control tones to switch the call to any destination without the provider’s knowledge.
As technology advanced, electronic devices known as “blue boxes” appeared, which could generate dozens of control tones, allowing for the manipulation of the entire call routing process. Phreaking quickly grew into a movement: university students, technology pioneers (including a young Steve Jobs and Steve Wozniak, who built and sold blue boxes), and even criminal circles profited from it. This led to the realization that in-band, audio-based control had to be separated from the voice channel and replaced with digital, encrypted protocols. This recognition resulted in the creation of the Signaling System No. 7 (SS7) protocol, which handled the transmission of control signals on separate, dedicated network channels. This brought an end to the classic era of phreaking, but as we will see, it also introduced new types of threats.
SS7 vulnerabilities and attacks on mobile networks
The introduction of the SS7 protocol at the end of the 20th century indeed solved the biggest problem of the phreaking era: instead of in-band (on-the-voice-channel) control, a separate, dedicated signaling channel was used for call routing and signaling between networks. The age of audio-frequency manipulation was effectively over. However, due to its own limitations, SS7 also brought new security risks.
When SS7 was originally created, the telecommunications infrastructure operated as a strictly closed, protected environment: the SS7 network only connected national telecommunications providers, where all participants were presumably trustworthy. However, with the rise of global mobile communication, roaming services, internet telephony, and market liberalization, this model changed. Today, not only large state-owned providers but also countless smaller, privately-owned telecommunications companies, service providers, and mobile aggregators have access to the SS7 signaling network.
The problem is that the SS7 protocol is fundamentally not properly authenticated or encrypted. There is no uniform mechanism within the network to verify whether incoming signals truly originate from a trusted party. The system is over four decades old and has a security architecture that is severely outdated compared to today’s threat level. Consequently, if an attacker gains access to the SS7 network—for instance, through a shadow provider or a corrupted smaller international partner—they can essentially freely send and receive signals that allow them to retrieve the location of mobile phones, redirect calls or SMS messages, and even enable eavesdropping. The greatest danger is that the attacks often remain completely unnoticed by the user and are difficult to detect on the provider’s side if there is no specific protection in place (e.g., SS7 firewalls, traffic analysis systems).
Thus, attackers can:
– Query the location data of mobile phones.
– Redirect SMS messages (e.g., bank authentication codes).
– Eavesdrop on mobile calls.
The vulnerabilities of the SS7 protocol were not just theoretical risks; they had severe real-world consequences. In 2017, German banks were defrauded when attackers exploited SS7 weaknesses to redirect two-factor authentication codes to their own devices and then used them to withdraw money from customers’ accounts. During the fraud, attackers first obtained login credentials using phishing emails and then stole the verification codes sent by the bank via SMS, all made possible by SS7-based message redirection. How can one defend against all this? Unicorn also offers solutions for protecting corporate mobile fleets and telecommunications infrastructure.
VoIP systems and SMS spoofing: Modern threats
VoIP vulnerabilities
The rapid spread of VoIP systems (e.g., corporate IP telephony using the SIP protocol) in recent years has brought significant advantages for companies: more cost-effective operation, flexible scalability, and easier integration with existing IT infrastructure. However, VoIP technology operating over the open IP network has also opened a new attack surface for cybercriminals.
If VoIP traffic is not properly encrypted, conversations can be eavesdropped on. Through a successful man-in-the-middle attack, attackers can leak sensitive business information (e.g., client meetings, internal discussions).
By hacking into improperly configured VoIP exchanges (IP-PBX systems), attackers can even make international calls at the company’s expense. This is known as VoIP toll fraud, which often occurs at night or on weekends when there is no active monitoring, and can cause damages of several thousand euros in a single night.
- Additionally, with VoIP DoS (Denial of Service) attacks, attackers can paralyze a company’s entire telephone customer service. During a well-timed DoS attack, calls are flooded with fake traffic, so real customer calls cannot get through. This can be particularly critical for financial service providers, healthcare institutions, or emergency centers.
SMS spoofing
The SMS protocol is not immune to attacks either. Unfortunately, the sender ID (Caller ID) when sending SMS messages can be easily falsified. This is exploited by attackers in one of the most common types of attacks, known as smishing.
The attacker can send an SMS in the name of your bank, a well-known service provider, or even a government authority, containing a malicious link or false instructions. Since the spoofed sender appears trustworthy on your phone, many users unsuspectingly follow the instructions, thereby easily giving access to their data or initiating financial transactions.
This method is particularly dangerous because SMS is also used in many systems as a second authentication factor (2FA), so SMS spoofing can even allow attackers to bypass two-factor authentication.
Defense
Unicorn’s network security package includes the encryption of VoIP traffic, including the application of SIP over TLS (encrypting signals) and SRTP (encrypting the voice stream) protocols. Furthermore, Unicorn’s experts also perform configuration audits of IP-PBX systems to eliminate vulnerabilities through which VoIP fraud or DoS attacks could be executed.
IoT: The future challenges in telecommunications security
The communication of IoT devices (such as sensors, smartwatches, vehicles, industrial equipment) also takes place over telecommunications channels like mobile networks, Wi-Fi, or other wireless technologies. Unfortunately, many manufacturers do not pay enough attention to built-in security, making these devices easy targets.
A few well-known cases illustrate the risks:
– 2016 – Mirai botnet: Hundreds of thousands of unprotected IoT devices were enlisted into a massive DDoS attack that paralyzed well-known web services.
– 2015 – Jeep hack: Ethical hackers demonstrated that a Jeep Cherokee vehicle could be controlled remotely over a mobile network channel—including critical functions like braking.
Defense: One of the key areas for Unicorn’s system integration and network security team is the protection of IoT networks. To achieve this, we apply the following solutions:
– Creating private APNs on the mobile network for the separated and protected data traffic of IoT devices.
– Network segmentation to ensure IoT devices operate separately from critical systems.
– Monitoring IoT device traffic and anomaly detection.
– Supervising manufacturer updates to close vulnerabilities as quickly as possible.
Unicorn regularly implements these solutions for its industrial clients as well, to prevent smart devices from becoming entry points for attackers into the corporate network.
Why Is protecting telecommunication channels still important today? – Summary
The more than 180-year history of telecommunications hacking clearly shows that every technological innovation brings with it a new attack surface. Throughout the evolution of telecommunications systems, there have always been those who tried to obtain information or manipulate systems through communication channels.
Although most companies today use a digitally mature infrastructure, the protection of telecommunications channels is still not a given. Many are inclined to think that the service provider “handles everything”—but this is only partially true. There are numerous factors whose protection falls within the company’s own responsibility:
– Without proper configuration and encryption of VoIP systems and IP-PBX exchanges, business calls can become vulnerable.
– The secure use of mobile fleets, monitoring application usage, and applying MDM systems are unavoidable in today’s mobile workplaces.
– Due to the vulnerabilities of the SMS protocol, it is still important to build appropriate security controls for SMS-based communications.
– With the spread of IoT devices, companies are connecting more and more physical processes to the network—the vulnerability of which is often underestimated.
All this means that telecommunications security is no longer just a technical issue, but also a business risk factor. It is important for business leaders to recognize that the telecommunications infrastructure is no longer an isolated island, but an integral part of the IT network. Accordingly, the same security principles—regular audits, traffic monitoring, encryption, user education—must be applied to it as to any other IT system. The examples of the past—from the 1834 optical telegraph manipulation through modern VoIP DoS attacks to SMS spoofing—clearly send the message: attackers always try to enter at the least protected point. Today, this could be an improperly configured IP-based phone system, an unprotected IoT device, or a weak point in the mobile network.
The key to a future telecommunications security strategy is therefore this: do not treat telecommunications channels as a secondary area of importance. On the contrary, integrate their protection into the corporate IT security strategy and ensure that it has up-to-date protection. This is where Unicorn can help: the protection of the telecommunications infrastructure is just as much a part of the company’s IT security approach as classic network or data protection. The goal in every case is for companies to manage this risk area consciously and proactively. The lesson of the past is simple: there will always be new attack methods; the only question is whether we are prepared for them.