🚨 IMEI: Smartphone Unique ID Number and Security Importance

Today Korean Social News | 2025.05.26

📌 SKT Hacking: IMEI Data Leak Concerns...SIM Protection Service Weakening Fears

💬 In the SK Telecom hacking incident, a server storing about 290,000 IMEI (device unique ID numbers) was infected with malware. The government says it cannot confirm whether this information was actually leaked, and SKT denies the possibility of a leak. However, experts worry that if both IMEI and IMSI (subscriber ID numbers) are leaked together, SIM protection services may become less effective. This incident has once again highlighted the importance of personal data protection and communication security.

Summary

• IMEI is a unique 15-digit identification number given to all mobile devices worldwide.
• It works like a 'social security number' for smartphones and is used for loss reports and theft prevention.
• Telecom companies use IMEI to identify devices and manage network access.

1️⃣ What is IMEI?

IMEI (International Mobile Equipment Identity) is a unique 15-digit identification number given to all mobile communication devices worldwide. Simply put, it's like a 'social security number' for your smartphone.

This number is assigned by manufacturers when the device is made, and it's completely unique - no two devices in the world have the same IMEI.

💡 Why is it important?

• When your smartphone is lost or stolen, this number helps identify and block the device.
• Telecom companies use it to check if a device is legitimate before allowing network access.
• It helps block illegal copied devices or hacked phones.
• It serves as the first line of defense for personal data protection and communication security.

2️⃣ IMEI Structure and Functions

📕 How IMEI Numbers are Made

• IMEI has 15 digits, and each part has a specific meaning. The main structure is:

  • First 8 digits (TAC): Type Approval Code - identifies the manufacturer and model.
  • Next 6 digits (SNR): Serial number - distinguishes individual devices of the same model.
  • Last 1 digit (CD): Check digit - verifies that the number is valid.
  • For example, in '123456789012345': '12345678' is TAC, '901234' is SNR, and '5' is the check digit.

• There are several ways to check your IMEI. Main methods include:

  • Dial '*#06#' on your phone to see it immediately.
  • Go to smartphone Settings → General (or Device Info) → Phone Information.
  • For phones with removable batteries, it's printed under the battery.
  • It's also written on the device box or purchase receipt.

📕 Main IMEI Functions and Uses

• IMEI is used for many different purposes. Main functions include:

  • Loss/Theft Reports: When you report a lost phone to police or telecom companies, they use IMEI to block the device from networks.
  • Network Access Management: Telecom companies check IMEI to verify legitimate devices before providing service.
  • Preventing Illegal Copies: Detecting and blocking fake devices with copied IMEI numbers.
  • Service and Warranty: Manufacturers use IMEI to check device production date, model, and warranty status.

• IMEI management is organized by country. The management system works like this:

  • In Korea, the Korea Communications Commission oversees IMEI management.
  • Telecom companies work together to maintain a database of lost/stolen devices.
  • Internationally, GSMA (GSM Association) manages IMEI assignment.
  • There's also an international cooperation system to block illegal devices.

Main IMEI Security Risks

1. Personal Data Leaks: If IMEI is leaked, your device usage patterns can be tracked.
2. Spoofing Attacks: Hackers can copy someone else's IMEI to illegally use communication services.
3. SIM Protection Service Weakening: If both IMEI and IMSI are leaked together, security services become much less effective.
4. Location Tracking: IMEI can be used to track your movements and location.
5. Financial Fraud: Copied IMEI can be used to hack mobile banking services.

3️⃣ IMEI Security Incidents and Response Plans

✅ Recent Security Incident Status

• IMEI leaks from telecom company hacking are happening. Main incident status:

  • In the 2025 SK Telecom hacking incident, servers storing about 290,000 IMEI records were infected with malware.
  • Overseas, there have been cases where millions of IMEI records were leaked through telecom database hacks.
  • Cases of IMEI collection and misuse through illegal apps are also increasing.
  • IMEI information is sometimes misused in used phone transactions.

• The impact of IMEI leaks is serious. Main effects include:

  • Personal communication patterns and location information can be tracked.
  • Copied IMEI can be used for illegal communication service access.
  • Mobile banking and electronic payment service security can be compromised.
  • Existing security services like SIM protection become less effective.

✅ Personal Protection Methods and Response Plans

• Individual efforts to protect IMEI are needed. Main protection methods:

  • Don't share your IMEI number carelessly with others.
  • When buying/selling used phones, IMEI checking is necessary, but be careful not to share it online publicly.
  • Refuse requests for device information from suspicious apps or websites.
  • Regularly check your telecom company's security service subscription status.

• Response measures from telecom companies and government are also being strengthened. Main responses include:

  • Telecom companies are strengthening IMEI information encryption storage and access control.
  • The government strictly regulates collection and use of unique identification information like IMEI through personal data protection laws.
  • Illegal copied IMEI detection systems are continuously being improved.
  • International cooperation systems are being built to respond to IMEI-related cybercrimes.

4️⃣ Related Terms Explained

🔎 IMSI (International Mobile Subscriber Identity)

• IMSI is a unique identification number for subscribers stored on SIM cards.
• IMSI (International Mobile Subscriber Identity) is a unique identification number for subscribers stored on SIM cards. While IMEI identifies the device, IMSI identifies the communication service subscriber.
• IMSI consists of 15 digits: the first 3 digits are the country code (MCC), the next 2-3 digits are the network code (MNC), and the rest is the subscriber number (MSIN). For Korea, the country code is 450, with SKT using 05, KT using 08, and LG U+ using 06.
• IMSI is very important security information that regular users cannot easily check. If both IMEI and IMSI are leaked together, hackers can identify both a specific user's device and communication service, making it very dangerous for security. This can greatly limit the effectiveness of existing security measures like SIM protection services.

🔎 SIM Protection Service

• SIM protection service is a security service that prevents SIM card copying or replacement.
• SIM protection service is a security service provided by telecom companies that prevents SIM cards from being copied or moved to other devices without the subscriber's consent. This service is especially effective in preventing SIM swapping fraud through smishing or phishing attacks.
• Main functions of SIM protection service include: First, strengthening identity verification procedures when reissuing SIM cards. Second, requiring authentication procedures when using SIM cards in new devices. Third, immediately blocking suspicious SIM card activity and sending notifications to subscribers.
• However, if both IMEI and IMSI information are leaked together, hackers can disguise themselves as legitimate users, greatly limiting the effectiveness of SIM protection services. Therefore, telecom companies are introducing additional security authentication methods beyond simple IMEI and IMSI verification.

🔎 Smishing (SMS + Phishing)

• Smishing is a fraud method using text messages to steal personal information.
• Smishing combines SMS (text messages) and phishing, sending fake website links through text messages to steal personal information or install malicious apps. Recently, it's also being used to steal IMEI information.
• Main smishing methods include: First, sending fake texts disguised as delivery notifications or card approval alerts. Second, when you click links in the text, you're connected to fake websites that try to get you to enter personal information. Third, making you download malicious apps that steal information from your smartphone.
• If IMEI information is stolen through smishing, hackers can identify the victim's device information and attempt more sophisticated fraud. To prevent this, don't click links from unknown text messages, only download apps from official app stores, and install security programs on your smartphone.

5️⃣ Frequently Asked Questions (FAQ)

Q: What risks exist if someone else knows my IMEI number?

A: While immediate damage doesn't occur just from knowing the IMEI number, there are several security risks. First, your device usage patterns and location information can be tracked. Second, when combined with other personal information, it can be used for more sophisticated fraud. Third, hackers might copy your IMEI to illegally use communication services. Fourth, it can be misused in used phone transaction fraud. Therefore, you should not share your IMEI number with others unless absolutely necessary (like loss reports or service requests). You should especially avoid sharing your IMEI number online. If you suspect your IMEI number has been leaked, contact your telecom company to consider additional security services and regularly check for suspicious activity.

Q: Can I find my smartphone using IMEI if it's lost?

A: IMEI itself cannot directly track your smartphone's location. However, IMEI plays a very important role in loss reports and device blocking. When reporting a loss, if you provide the IMEI to police or telecom companies, the device will be blocked from networks when it tries to connect, preventing others from using it. Actual location tracking is possible through location tracking services installed on smartphones (like iPhone's 'Find My' or Android's 'Find My Device'). These services use GPS, Wi-Fi, and cell tower information to locate devices. Therefore, it's good to activate location tracking services in advance and separately record your IMEI number in preparation for smartphone loss. When lost, immediately report to telecom companies and police to block the device, and use location tracking services to find the device.