Impersonating a subscriber using techniques reminiscent of SIM swapping has become a pressing subject in the telecom world. The most impactful method relies on the SS7 Server as a crucial component for orchestrating such operations.
Understanding how these activities unfold within mobile networks is vital for anyone working in telecommunications security. By exploring the mechanisms that enable impersonation, industry professionals can better comprehend the landscape they are navigating.
How SS7 Enables SIM Swap-Like Impersonation
The SS7 (Signaling System No. 7) protocol is a foundational element of the world’s communication infrastructure. Designed decades ago, SS7 coordinates how different mobile operators exchange information such as SMS routing, call setup, subscriber location, and mobile number portability. It serves as a trusted path between networks, but its trust-based architecture has made it an attractive target for misuse.
To impersonate a subscriber in a manner analogous to a SIM swap, a threat actor exploits the SS7 protocol’s ability to update subscriber information. Normally, when a legitimate SIM swap request is processed—for instance, when a user loses a phone and gets a new SIM—the network updates its records with the new SIM card details associated with the user’s account. However, by injecting false requests into the SS7 network, a malicious actor can redirect a victim’s calls and messages to a device of their choosing without the victim’s knowledge.
This process typically involves sending a special update message known as an “Update Location” request. By leveraging access to an SS7 Server, the intruder can instruct the telecom network to recognize a rogue device as the legitimate one associated with the victim’s phone number. This effectively enables the attacker to receive calls, two-factor authentication texts, and other communication intended for the victim.
Behind the Scenes: The Technical Process
At the heart of SS7-based impersonation lies the ability to communicate with the global telecommunications backbone. Networks implicitly trust messages received from within the SS7 system. An attacker, with the right access, can masquerade as another operator or as a partner node, bypassing typical authentication checks.
Once access is established, a threat actor can issue commands that replicate the effects of a SIM swap. These commands are essentially data packets containing the victim’s International Mobile Subscriber Identity (IMSI) and associated mobile number. By manipulating the information associated with the IMSI, the network diverts message delivery and call routing to the attacker’s device. Since this happens at the infrastructure level, the victim’s phone continues to function—often without showing signs of unauthorized actions—while sensitive communication is silently redirected.
Another factor contributing to the effectiveness of this approach is the international scope of the SS7 protocol. Because telecom networks across the world rely on interconnected SS7 messaging, the scope of impersonation extends beyond local networks and can impact subscribers regardless of their physical location.
Real-World Implications and Global Reach
The use of SS7-based techniques for impersonation is not just theoretical. There have been documented cases globally where attackers exploited SS7 access to compromise bank accounts, bypass two-factor authentication, and intercept confidential information for financial theft.
For mobile network operators, the threat landscape continues to evolve as more interconnected systems come online. Subscribers may believe they are safe as long as their SIM card remains physically in their possession, but the underpinnings of the global telecom infrastructure introduce new avenues for risk. Attackers need not gain physical access to the SIM; rather, network protocol manipulation is sufficient for impersonation.
What makes this issue particularly concerning is the indirectness of the attack. Since subscribers may receive incoming calls and some SMS as usual, they may not realize any compromise has occurred until suspicious activities come to light, often in the form of unauthorized financial transactions or account lockout notifications.
Conclusion
Impersonating a subscriber through SS7 acts as a potent demonstration of the vulnerabilities inherent in legacy telecom systems. By leveraging trusted signaling arrangements and the connected nature of modern telecom infrastructure, attackers can orchestrate operations similar to traditional SIM swaps—with broader reach and less visibility to the victim.
Remaining aware of these mechanisms is essential for telecommunication professionals and end-users alike. By understanding how SS7 enables this style of impersonation, organizations can reevaluate their security postures and work to minimize risk as mobile communication continues to evolve worldwide.