What Is IMSI Number?

IMSI, or International Mobile Subscriber Identity, is a unique identification number given to each mobile phone user. Mobile operators use this number to identify and authenticate phone network subscribers. IMSI number is the lynchpin of all mobile phone operators. This number allows you to make phone calls at home and abroad and protect your mobile identity from theft. Let’s explore what makes an International Mobile Subscriber Identity Number so special.

What Is IMSI?

The unique International Mobile Subscriber Identity (IMSI) number is a combination of 15 digits, though their number can sometimes be shorter. It comprises the Mobile Country Code (MCC), the Mobile Network Code (MNC), and the Mobile Subscriber Identification Number (MSIN).

Where Is the IMSI Number Stored?

The number is stored on the mobile phone SIM card. It contains the user’s personal identification and other critical information required to identify and authenticate a subscriber of a phone operator. When your cell phone is powered on, it automatically attempts to connect to your respective phone operator. To do that, it reads the IMSI number from the SIM card.

When the connection is established, your phone sends an IMSI code to the grid. This usually happens during the initial grid attachment process. First, the operator uses an IMSI number to identify the subscriber. After that, the phone operator authenticates their access and determines their service entitlements and billing information. To ensure security and privacy, the IMSI number is generally not used for ongoing communication after the initial handshake. Instead, the system provides you with a Temporary Mobile Subscriber Identity (TMSI) number used for most phone-operator communications, minimizing the risk of exposing the identification over the air.

Why Is IMSI Number so Important?

An IMSI number is vital for many processes. It allows the phone operator to check your associated profile. Moreover, the number contains the details of your subscription plan, service entitlements, and billing information. Thanks to this, the phone operator can provide you with the services you pay for, such as voice, text, data, and additional features.

An IMSI number is essential in international phone roaming. When you travel to a different country, its operators use this number to recognize and authenticate you as a member of a foreign grid, thus ensuring phone mobile services are available to you when you are not within the coverage area of your home grid. The phone operator in the country you visit is in contact with your home network to verify your credentials and manage billing for the roaming services you use there.

How do IMSI Numbers and IMEI Numbers differ?

An IMSI number and an IMEI (International Mobile Equipment Identity) number are identification codes, but they have distinct roles in communication. The former number identifies the user within the mobile grid. An IMEI number, in contrast, is the identification of the cell phone. It is a hardware-specific number embedded by the phone manufacturer. An IMEI number helps track and manage phones on the grid, including blocking stolen or lost phones.

The main role of an IMEI number is the phone’s integrity and security. This number allows phone operators to identify and block stolen phones, preventing their unauthorized use regardless of the SIM card inserted. This is useful for preventing phone theft and managing the operator’s inventory of phones.

Another key difference lies in the use and visibility of numbers. The phone’s IMSI number is primarily used internally within the grid and is not visible to the end user. It is transmitted over the air during the initial connection to the phone operator but is otherwise protected to prevent unauthorized access and tracking. Conversely, an IMEI number is visible to users and can be accessed by entering a specific code on the device (usually *#06# on most phones) or through the phone settings.

How to Find an IMSI Number

Checking your phone’s IMSI number is easy. Usually, it’s stored on your cell phone’s SIM card. The fastest way to check your number is to access phone settings. On Android phones, you can find the IMSI number by opening "Settings" → "About phone" → "Status"/"SIM status." Here are all the details about your phone SIM card, including the IMSI number. On iOS phones, you can find your phone’s IMSI number by opening the "Settings" app, selecting "General," then "About." Once there, look for the "ICCID" or "IMSI number" field. However, it's worth noting that an IMSI number is not always openly displayed on all phones for security reasons.

If you can’t find your IMSI phone number in the device's settings, try using specialized apps. For Android, there are apps like "IMSI Checker" or "SIM Card Info." There are similar iOS apps on the App Store.

Sometimes, an IMSI phone number might be printed directly on the phone’s SIM card. If this is the case, simply remove the SIM card from the device and inspect it for any printed numbers that might include the needed number.

If you can’t find your IMSI code number using the methods above, contact your mobile phone operator. Customer support representatives can access subscriber information and provide an IMSI number after verifying your identity.

What Do These 15 Number Digits Mean?

The first 3 digits of an IMSI number are the Mobile Country Code (MCC). It identifies the subscriber’s country. For instance, the MCC for the United States is 310, and 243 for the UK.

The following 2 or 3 number digits are MNC. The Mobile Network Code identifies the specific phone operator within the country. In North America, MNC typically has three digits, while in the rest of the world, it usually has two. For example, an MNC of 150 in the United States would identify a specific phone operator within that country.

The remaining digits of an IMSI phone number are the Mobile Subscriber Identification Number (MSIN). This segment uniquely identifies the subscriber within the phone network operator’s system. The length of this number is adjusted to ensure the total length of an IMSI code number is 15 digits when combined with MCC and MNC.

To illustrate, consider an IMSI number of 310150123456789. Here, the MCC number is 310, indicating the United States. MNC number is 150, specifying a particular phone network operator within the United States. MSIN number is 123456789, uniquely identifying the subscriber within that phone network.

Risks Associated with IMSI Number Leaks

If your phone’s IMSI number leaks, your privacy and security become compromised, leaving you open to unauthorized surveillance and more. For starters, cell phone networks constantly monitor the locations of devices to provide connectivity. If your identification is leaked, anyone can use it to trace the movement of your cell phone. Unauthorized parties can continuously and precisely track your daily routes. It can reveal your daily habits, frequently visited locations, and even personal and professional associations.

There are many ways to use phone IMSI numbers for illegal activities. One such method is using IMSI number catchers or “Stingrays.” It implies legitimate cell towers and tricking cell phones nearby to connect to them. Once connected, the attacker can intercept your phone calls, messages, and traffic. This way, they can obtain your sensitive information, such as personal conversations, financial transactions, and login credentials.

IMSI phone number leaks can be used for targeted attacks. Attackers who know you can plan and execute attacks tailored to you, specifically. For example, they might use social engineering techniques to trick you into revealing additional information or install malware on your cell phone. As a result of such attacks, your personal, corporate, and financial data can leak to fraudsters.

Another risk is mass surveillance. Governments and law enforcement agencies can use IMSI number catchers to spy on entire populations in a specific area. Normally, this is for a good reason, such as tracking criminals via their phones. But if IMSI number catchers are misused or criminals get access to them, it may infringe on civil liberties and human rights.

Lastly, a leaked IMSI number can be used for denial-of-service (DoS) attacks. An attacker who knows your phone’s IMSI number can flood the phone network with connection requests from that particular number. It can potentially create a security breach. If successful, it disrupts your cell phone, leading to potential harm, especially if you use your device for critical communications.

In conclusion, the phone’s IMSI number is a cornerstone of mobile telecommunications. This number is used for subscriber authentication and service provision, both in your home region and abroad. If your IMSI number gets leaked, you might face privacy breaches, security vulnerabilities, and unauthorized surveillance. Take extra care to protect your IMSI number. Make sure to use robust security protocols and avoid exposing your IMSI during communication. This will ensure your privacy and safety.