How to Construct Your Own Base Station for GSM Interception: A Step-by-Step Guide

Introduction:

Ever wondered if it is possible to build your own GSM base station? This piece serves as an enlightening guide on how to decrypt the A5/1 air communication encryption and construct your own base station. This method operates on full duplex mode, allowing simultaneous transmission and reception of signals.

This post aims to highlight the security vulnerabilities in GSM (Global System for Mobile Communications) technology – not to be mistaken with advanced systems such as LTE (Long Term Evolution). Unprotected access to this method means potential for unauthorized intrusions over the years. This guide seeks to alert telecom companies and relevant authorities about these risks.

Building the Base Station:

I recently visited my friend and colleague, Ziggy, in Tel Aviv. During my visit, he presented me with a long-awaited gift, a brand new bladeRF x40. This low-cost Software Defined Radio operates in full-duplex, meaning it can transmit and receive simultaneously.

With some basic, affordable electronic equipment, you can design something that closely resembles what governments have been using for years for GSM interception. However, this post isn’t intended to aid amateurs in lawbreaking activities, but rather it aims to bring attention to GSM’s inherent flaws and emphasises the urgency for vendors to address these issues.

Hardware Requirements:

To build your base station, you’ll need specific hardware:

1. bladeRF x40
2. Two Quad-band Cellular Duck Antennas SMA.
3. Raspberry Pi 3 (model 2 and older models are too slow).
4. USB battery pack (I used a 26800mAh Anker Astro E7).
5. MicroSD for the RPI, minimum 8GB.
6. Patience and time.

Software Requirements:

You’ll be installing the latest Raspbian image to the microSD card, configuring the WiFi or Ethernet, and at the end of this process, you should be able to SSH into the RPI.

Following this, install the dependencies you’ll need, including BladeRF, libbladeRF-dev, libbladeRF0 automaker, etc. You should at this point be able to interact with the BladeRF by plugging it into one of the USB ports of the RPI.

Ensure that you have the correct versions of the firmware and the FPGA because other versions might not perform optimally in this setup.

Configuring Your BTS:

After installing Yate and YateBTS, two open-source softwares that are integral for crafting your BTS, the next step is configuring your BTS. With the necessary hardware and software in place, your BTS is good to go. All GSM phones in your vicinity will connect to your BTS thanks to its powerful signal strength.

Concluding Thoughts:

This setup allows you to configure your BTS to suit various needs. You could either employ it as a proxy to a credible SMC (Specialized Mobile Radio) and observe the unbroken GSM traffic of each phone or establish a private GSM network where users can interact freely using Session Initiation Protocol (SIP).

That said, the use of this information for criminal activities is not encouraged, and the providers of this information shall not be held liable for any damages that may arise.

This article was updated in 2025 to reflect modern realities.