--- Warning ---

This article is only for educational purpose. I didn't harm anyone. I used my own lab during explain of this method, so please don't use this type of method for any kind of illegal activities. I don't support any kind of illegal hacking.

How to use an IMSI Catcher to Intercept GSM Network

August 24, 2020

This article provides practical information for how to sniff calls, sms and mobile location using a IMSI Catcher. Recently, Hackers have been using IMSI Catcher device to hack a Cellular Network and text message sniffing to steal bank cards.

What is IMSI :

IMSI is also known as International Mobile Subscriber Identity (IMSI). IMSI is a globally unique number for each subscriber. The IMSI number consists of 15 digits, first 3 digits are Mobile Country Code (MCC), 2 digits are Mobile Network Code (MNC) and last 10 digits are Mobile Subscriber Identification Number (MSIN). The IMSI number is stored in the Subscriber Identity Module (SIM).

Generations of Mobile Phone :

1G :

1G is first generation mobile network was introduced in 1979. The radio signals used by 1G network are analog and without encryption (no encryption). Text messaging was not yet possible at 1G network.

2G :

2G is second generation cellular telecom networks were commercially launched on the GSM standard in 1991. 2G networks are radio signals became digital and the data is encrypted (weak encryption like a5/1, a5/3 etc). The 2G network features are such as data (GPRS, EDGE), SMS, MMS, voice mail and call forwarding were implemented. Also Later 2.5G and 2.75G were introduced and both implemented improved techniques for data transfer such as GPRS and EDGE. In general, the Global System for Mobile Communication (GSM) are used for most mobile phone protocol.

3G :

3G is third generation mobile network was introduced in May 2001. 3G network are radio signals become digital and data is encrypted (stronge encryption). 3G network features are internet speed up to 2 Mbps sach as, Increased bandwidth and data transfer rates, Send/receive large email messages, Large capacities and broadband capabilities. 3G mobile networks support Global positioning system (GPS), mobile television (LIVE TV) and video conferencing.

4G :

4G is fourth generation mobile network was introduced in 2009. 4G network are improved encryption standards (very strong encryption). 4G network features are internet speed up to 100Mbps sach as, Support interactive multimedia, voice, video, wireless internet and other broadband services. High speed, high capacity and low cost per bit. Global mobility, service portability, scalable mobile networks.

5G :

5G is fifth generation mobile networks were commercially launched in 2018. 5G network internet speed of up to 10Gbps and Beyond speed improvement, 5G is expected to unleash a massive IoT (Internet of Things).

Architecture of GSM :

What is an IMSI Catcher :

An IMSI catcher or international mobile subscriber identity-catcher, is a telephone eavesdropping device used for intercepting cellular mobile phone traffic and tracking location data of mobile phone users. IMSI Catcher operates on a fake mobile phone tower between the target mobile phone and the real towers of the service provider, it is considered a man-in-the-middle (MITM) attack. The 3G or 4g wireless cellular network mutual authentication required from both the handset and the network. However, but may be able to downgrade 3G and LTE to non-LTE network services which do not require mutual authentication.

Required Hardware and Software :

Hardware :

USB DVB-T key (RTL2832U) with antenna (less than 15$) or HackRF one or USRP.

Software & OS :

GR-GSM or Sigintos.

Capturing or Intercept of GSM traffic :

Capturing of GSM traffic :

Capturing and Sniff calls, sms of GSM traffic :

Detection of IMSI Catcher :

There are different applications available, which help to find the IMSI Catcher in your location. Once it is installed in mobile, it will automatically detect the IMSI Catcher. Applications contain a database of all the cell towers of mobile carriers in different countries and regularly update this list.

● Android IMSI-Catcher Detector
● SnoopSnitch
● Cell Spy Catcher
● GSM Spy Finder

Warning :

This article is only for educational purpose. I didn't harm anyone. I used my own lab during explain of this method, so please don't use this type of method for any kind of illegal activities. I don't support any kind of illegal hacking.