An In-Depth Guide to SS7 Attacks

September 28, 2024

Disclaimer: This guide is intended strictly for educational purposes, primarily to raise awareness about SS7 vulnerabilities. It should not be used for illegal activities or unauthorized access to telecom networks. Misuse of this information can lead to legal consequences. Always obtain proper authorization before testing telecom systems.

What is SS7?

SS7 (Signaling System 7) is a globally used protocol suite responsible for communication between telephone networks. It enables various critical functions in telecom systems like call forwarding, SMS messaging, number translation, and mobile roaming across different networks.

While SS7 was initially designed with only trusted network operators in mind, the protocol lacks advanced authentication and encryption mechanisms. This oversight has made SS7 vulnerable to several attacks, exposing mobile networks to risks such as eavesdropping, call interception, and location tracking.

Why SS7 is Important in Telecommunications

SS7 plays a significant role in modern telecommunications by ensuring that different telecom networks can communicate with each other. Without SS7, many everyday functions like international calls, SMS delivery, and mobile roaming would be impossible.

The key functions of SS7 include:

Call Management: Controls voice calls over telecom networks.
SMS Delivery: Ensures the successful delivery of text messages.
Mobile Roaming: Helps users remain connected when switching between networks, especially during travel.
Billing: Facilitates real-time billing for telecom services.

Understanding SS7 Vulnerabilities

The SS7 protocol was designed at a time when telecom networks were considered secure environments. However, with the introduction of newer technologies and broader access to telecom infrastructure, attackers can exploit vulnerabilities in SS7 to compromise user privacy and network security. Some of the critical vulnerabilities include:

Lack of Authentication: SS7 doesn’t authenticate incoming requests properly, meaning attackers can send fraudulent requests without verifying their identity.
No Encryption: SS7 messages are transmitted in plain text, which makes it possible for attackers to intercept sensitive data.
Interconnected Networks: Since SS7 operates between networks (domestic and international), attackers can use less secure networks as a gateway to infiltrate more secure networks.

How SS7 Attacks Work

SS7 attacks exploit the protocol’s vulnerabilities to intercept calls, SMS messages, and track the location of mobile users. Below are the common types of SS7 attacks:

1. Location Tracking

Objective: Track the real-time location of the victim.

How it Works: Using a specific type of request (e.g., SendRoutingInfo), attackers can query the victim’s mobile network to obtain their International Mobile Subscriber Identity (IMSI) and approximate location.
Impact: The attacker can continuously monitor the victim’s movements across the world.

Steps:

Send a SendRoutingInfo request to the Home Location Register (HLR) of the victim’s network.
The HLR responds with information on the victim’s current Mobile Switching Center (MSC), which can be used to determine their location.

2. Call Interception

Objective: Intercept and eavesdrop on phone calls.

How it Works: Attackers can manipulate the call forwarding feature by sending a request to redirect calls to a device under their control.
Impact: The attacker can listen in on live phone conversations between the victim and other parties.

Steps:

Send a MapForwarding request to the victim’s network to reroute incoming calls to a phone number controlled by the attacker.
Calls intended for the victim are intercepted by the attacker’s phone.

3. SMS Interception

Objective: Steal SMS messages, including two-factor authentication (2FA) codes.

How it Works: By sending fraudulent requests to the SMSC (Short Message Service Center), the attacker can redirect SMS messages meant for the victim.
Impact: This can be used to steal OTPs (One-Time Passwords), 2FA codes, and other sensitive information.

Steps:

Send a SendRoutingInfoForSM request to the victim’s SMSC.
Alter the delivery route of SMS messages to the attacker’s MSC.
Read intercepted messages and data.

4. Denial of Service (DoS) Attack

Objective: Render the victim’s mobile phone useless by disconnecting it from the network.

How it Works: Attackers can send a PurgeMS request to the victim’s mobile network, which forces the network to “forget” the victim’s phone, effectively cutting off their connection.
Impact: The victim will not be able to make calls, send/receive SMS, or access mobile data.

Steps:

Send a PurgeMS request to the HLR.
The victim’s mobile device loses connection to the network and becomes unavailable.

Tools Used in SS7 Attacks

Several tools are used in testing SS7 vulnerabilities in ethical hacking. These tools simulate attacks and test the robustness of telecom networks. Some of the widely used tools are:

SS7MAPer: A tool used for testing and exploiting SS7 vulnerabilities, particularly location tracking.
Wireshark: A popular packet-sniffing tool that captures and analyzes SS7 traffic.
Yate: Yet Another Telephony Engine, commonly used to build SS7 signaling systems for testing.

Ethical Use of SS7 Tools

As an ethical hacker, you must use SS7 tools responsibly. Any unauthorized exploitation of telecom networks can result in serious legal consequences. Always ensure that you are working within a simulated environment or have explicit permission to test a network.

Real-World Examples of SS7 Attacks

Several high-profile SS7 attacks have occurred in recent years, shedding light on the vulnerabilities in the protocol:

Banking Fraud via SMS Interception: In 2017, cybercriminals in Europe exploited SS7 to intercept SMS-based banking verification codes. This allowed them to withdraw money from users’ bank accounts.
Political Espionage: In 2016, hackers used SS7 to spy on politicians by intercepting their phone calls and tracking their movements.

These examples highlight the critical need for telecom operators to secure SS7 networks.

Mitigating SS7 Attacks

While SS7 vulnerabilities are challenging to eliminate, several strategies can mitigate the risks:

SS7 Firewalls: Telecom providers can implement SS7-specific firewalls that monitor and filter malicious requests.
Message Filtering: Operators should employ advanced filtering mechanisms to block unauthorized access requests.
Encryption and Authentication: Modern networks should implement encryption and authentication protocols like Diameter (used in LTE networks) to prevent unauthorized access.
Audits and Monitoring: Regular audits of SS7 traffic should be conducted to detect and address suspicious activity.

Legal and Ethical Considerations

When dealing with telecom networks and protocols like SS7, there are strict legal regulations to follow. Unauthorized access to SS7 networks is illegal in most countries, and violations can lead to severe penalties, including imprisonment.

Ethical hacking students should always:

Obtain permission before performing any telecom network tests.
Understand the laws regarding hacking and network security in their region.
Stay updated on ethical guidelines provided by organizations like EC-Council, Offensive Security, and others.

Conclusion

SS7 attacks expose critical vulnerabilities in the global telecommunications system. Understanding how SS7 works and where its vulnerabilities lie is essential for ethical hackers and cybersecurity professionals. As mobile networks evolve, so must the security measures that protect against attacks on SS7 and other legacy protocols.

By learning how these attacks work and knowing how to defend against them, you can help safeguard both individual privacy and the integrity of global communications systems.

An In-Depth Guide to SS7 Attacks