Fake Base Stations – Telecom’s Open Front Door for Hackers

Introduction: A Threat Hiding in Plain Sight

Imagine a telecom intrusion so subtle it requires no password, no backdoor, and no malware. Just a piece of hardware that pretends to be a mobile base station—and mobile phones willingly connect to it. This is the world of fake base stations, also known as IMSI catchers or Stingrays.

These devices are not theoretical. They are deployed today—by police forces, hostile states, and organised crime networks. While some government use may be authorised, many fake base station deployments operate in a legal and technical grey zone that mobile network operators (MNOs) are often poorly prepared to detect or prevent.

This blog examines:

• How fake base stations are built and deployed

• Who uses them and why

• Their impact on user privacy and national infrastructure

• What operators and regulators can do to defend against them

How Fake Base Stations Work

At their core, fake base stations exploit a fundamental design flaw of the mobile network: the handset (User Equipment, or UE) assumes any base station it hears is legitimate—and connects to it based on signal strength, not authentication.

The typical process is as follows:

1. Signal Overpowering

The rogue base station emits a stronger signal than nearby legitimate towers. Mobile phones in range will preferentially connect to the stronger signal.

2. Network Impersonation

The device broadcasts as if it belongs to a real operator (for example, Vodafone UK or STC in Saudi Arabia). It can mimic LTE, 3G, or GSM protocols depending on the attacker’s tools.

3. IMSI Harvesting or Downgrade Attacks

Once connected, the fake base station can:

• Request the phone’s IMSI (International Mobile Subscriber Identity), a globally unique identifier.

• Force downgrade to less secure protocols such as 2G/GSM, where encryption is weak or absent.

• Intercept or manipulate traffic, particularly in voice, SMS, and data scenarios with minimal encryption.

4. Man-in-the-Middle Exploitation

Advanced versions act as relay stations—intercepting traffic between the phone and the real network. This enables:

• Call and SMS interception

• Internet traffic rerouting

• Malware injection

What’s the Hardware?

The components of a fake base station are now commercially available or open-source, often costing less than $1,000:

• Software Defined Radios (SDRs) such as HackRF or USRP

• Open-source baseband stacks (e.g., OpenBTS, srsLTE)

• Laptop or Raspberry Pi controllers

• Mobile antennas for concealment in briefcases, drones, or vehicles

High-end versions used by intelligence services are more advanced—multi-protocol, mobile-network-agnostic, and able to process thousands of connections simultaneously.

Who Uses Them—and Why

Law Enforcement and Intelligence Agencies

Used for lawful surveillance in some jurisdictions, often to track suspects or identify nearby phones. This is frequently done with limited public oversight.

State Actors

Deployed during protests, near embassies, or in conflict zones. Russian, Chinese, and other state-linked actors have reportedly used fake base stations in European capitals to track or intercept political targets.

Organised Crime

Deployed to:

• Clone SIM cards

• Defraud mobile operators

• Spy on rivals or law enforcement

• Trigger premium-rate scams or SIM swap fraud

Corporate Espionage

Used to intercept communications near corporate offices, hotels, or trade shows as part of competitive intelligence gathering.

The Impact: Beyond Privacy

Targeted Surveillance – Enables interception of calls and messages in real time.

Mass Tracking – Harvests IDs from thousands of devices at events or in specific areas, enabling mapping of attendance and associations.

Identity Theft and SIM Swaps – Facilitates cloning and fraud.

Operational Disruption – Can interfere with emergency communications, mobile payments, or IoT systems, creating potential safety risks.

Why Mobile Networks Still Struggle to Stop Them

Despite rising awareness, many mobile networks lack real-time detection capabilities for rogue base stations. Reasons include:

• No UE-side authentication in legacy networks (especially 2G/3G)

• Difficulty monitoring the radio access network at street level

• Limited authority over device manufacturers or grey-market sales

• Weak coordination between MNOs, regulators, and security agencies

Even in 5G, Service-Based Architecture (SBA) introduces new interfaces that can be spoofed or manipulated.

Countermeasures: What Can Be Done

1. Base Station Authentication5G includes mutual authentication between UE and network - if implemented correctly. MNOs must prioritise 5G SA rollout and enforce robust encryption.

2. Rogue BS DetectionDeploy systems that monitor anomalies in base station identity broadcasts, unusual signal patterns, and unexpected handovers. Tools include:

• Cell tower anomaly detection platforms

• Drive testing with IMSI catcher detection

• Crowdsourced mobile telemetry

3. End-User ProtectionEncourage high-risk users to:

• Use devices with IMSI catcher detection

• Use VPNs and encrypted messaging

• Avoid devices with 2G fallback

4. Policy and Regulation

• Sunset 2G networks entirely, as some nations have done

• Enforce penalties for unauthorised telecom interception tools

• Mandate incident reporting from MNOs to national cyber authorities

5. Red Teaming and SimulationConduct CyberDrills with simulated rogue base stations to train telecom SOCs and improve response playbooks.

Strategic Implications for Boards and Operators

Fake base stations are no longer a niche threat:

• They are accessible with modest resources

• They offer deniability and operational flexibility

• They are increasingly deployed against executives, governments, and critical sectors

Bridge Connect recommends that MNOs and regulators treat rogue base station detection and mitigation as a national security priority, given the role telecoms play in both economic stability and public safety.

Final Thoughts

Telecom networks were built on trust. In today’s environment, that trust cannot be assumed.

Fake base stations represent not just a technical problem but a business continuity, national security, and reputational risk.

The first step toward mitigation is visibility.

The second is strategy.

Bridge Connect supports operators and governments in building both.