What are the limits of phone number–based identity?
Posted: Thu May 22, 2025 9:25 am
While phone numbers are widely used as a form of identity verification, particularly for online services and two-factor authentication (2FA), they have significant limitations that make them an insufficient or fragile basis for robust identity proof. These limitations are increasingly exploited by fraudsters, leading to various forms of identity theft and account takeovers.
Here are the limits of phone number-based identity:
1. Lack of Inherent Identity Proof:
Not Unique to an Individual: A phone number is tied to a SIM card and a service subscription, not directly to an individual's immutable biometric or civic identity (like a fingerprint or a National ID card). While SIM registration processes, like Bangladesh's biometric SIM registration, aim to link numbers to NIDs, the number itself can be transferred or compromised.
Transient Nature: Phone numbers can be changed, ported to different carriers, or disconnected. This transient nature means a number may not always be associated with the same person over time.
Public Availability: Many phone numbers are publicly available through directories, social media profiles, or data breaches. This makes them easy targets for collection by malicious actors.
2. Vulnerabilities to Fraud and Account Takeovers:
SIM Swap Fraud: This is one of the most critical weaknesses. Fraudsters romania phone number list can convince a mobile carrier to transfer a victim's phone number to a SIM card they control. Once the SIM swap is successful, the attacker receives all calls and SMS messages, including one-time passcodes (OTPs) for 2FA, allowing them to reset passwords and gain access to banking, email, social media, and other online accounts linked to that phone number.
In Bangladesh: While biometric SIM registration was implemented to curb unregistered SIMs and criminal activity, loopholes or human errors in the verification process, as well as insider threats at carrier end, can still facilitate SIM swaps. NID server glitches or issues in the biometric verification process, as reported, can also create vulnerabilities.
Port-Out Scams: Similar to SIM swaps, but involves transferring the number to a different carrier, granting the fraudster control.
SMS Interception/Rerouting: Less common but possible, attackers can intercept SMS messages (including OTPs) through sophisticated network exploits (like vulnerabilities in the SS7 protocol) or malware installed on the device.
Social Engineering: Fraudsters can use a known phone number to conduct social engineering attacks, pretending to be a bank, service provider, or even a friend/family member, to trick the individual into revealing sensitive information or transferring money.
Public Records & Data Breaches: Phone numbers are frequently included in leaked databases from data breaches. Combined with other personal information (name, address, email), a phone number can be used to build a comprehensive profile for identity theft.
3. Over-reliance for Two-Factor Authentication (2FA):
Many online services still heavily rely on SMS-based 2FA, sending OTPs to a registered phone number. While better than no 2FA, this method is susceptible to SIM swaps and SMS interception.
Mitigation: The industry is moving towards stronger 2FA methods like authenticator apps (e.g., Google Authenticator, Microsoft Authenticator) or hardware security keys (e.g., YubiKey), which are not tied to the phone number directly and require physical possession of the device.
4. Limited Context and Granularity:
A phone number alone provides no context about the individual's current mental state, intent, or the specific context of their online activity.
It cannot distinguish between a legitimate user and someone who has illicitly gained control of their number.
5. Challenges in Detection for Fraud Prevention:
Difficulty in Real-time Verification: While services can check if a number is active, its type (mobile, landline, VoIP), or if it has been recently ported, accurately and instantly verifying that the current user of the number is its true owner remains a challenge.
Evolving Tactics: Fraudsters constantly adapt their methods, making it difficult for phone number-based security measures to keep pace.
6. Operational and Cost Burdens for Businesses:
Due to the limitations, businesses often need to implement multiple layers of authentication beyond just phone number verification, which adds complexity and cost to their operations and can impact customer experience.
In Bangladesh, where mobile penetration is extremely high and many digital services (e.g., Mobile Financial Services like bKash, Nagad) are heavily reliant on phone numbers and SMS OTPs, the vulnerabilities associated with phone number-based identity are particularly pronounced. The integration of NID with SIM registration was a step towards stronger identity, but persistent issues like the NID server glitches and potential for fraudulent SIM activation highlight that even with such measures, phone numbers are a fragile foundation for comprehensive identity verification. Relying solely on them is a significant risk for both individuals and service providers.
Here are the limits of phone number-based identity:
1. Lack of Inherent Identity Proof:
Not Unique to an Individual: A phone number is tied to a SIM card and a service subscription, not directly to an individual's immutable biometric or civic identity (like a fingerprint or a National ID card). While SIM registration processes, like Bangladesh's biometric SIM registration, aim to link numbers to NIDs, the number itself can be transferred or compromised.
Transient Nature: Phone numbers can be changed, ported to different carriers, or disconnected. This transient nature means a number may not always be associated with the same person over time.
Public Availability: Many phone numbers are publicly available through directories, social media profiles, or data breaches. This makes them easy targets for collection by malicious actors.
2. Vulnerabilities to Fraud and Account Takeovers:
SIM Swap Fraud: This is one of the most critical weaknesses. Fraudsters romania phone number list can convince a mobile carrier to transfer a victim's phone number to a SIM card they control. Once the SIM swap is successful, the attacker receives all calls and SMS messages, including one-time passcodes (OTPs) for 2FA, allowing them to reset passwords and gain access to banking, email, social media, and other online accounts linked to that phone number.
In Bangladesh: While biometric SIM registration was implemented to curb unregistered SIMs and criminal activity, loopholes or human errors in the verification process, as well as insider threats at carrier end, can still facilitate SIM swaps. NID server glitches or issues in the biometric verification process, as reported, can also create vulnerabilities.
Port-Out Scams: Similar to SIM swaps, but involves transferring the number to a different carrier, granting the fraudster control.
SMS Interception/Rerouting: Less common but possible, attackers can intercept SMS messages (including OTPs) through sophisticated network exploits (like vulnerabilities in the SS7 protocol) or malware installed on the device.
Social Engineering: Fraudsters can use a known phone number to conduct social engineering attacks, pretending to be a bank, service provider, or even a friend/family member, to trick the individual into revealing sensitive information or transferring money.
Public Records & Data Breaches: Phone numbers are frequently included in leaked databases from data breaches. Combined with other personal information (name, address, email), a phone number can be used to build a comprehensive profile for identity theft.
3. Over-reliance for Two-Factor Authentication (2FA):
Many online services still heavily rely on SMS-based 2FA, sending OTPs to a registered phone number. While better than no 2FA, this method is susceptible to SIM swaps and SMS interception.
Mitigation: The industry is moving towards stronger 2FA methods like authenticator apps (e.g., Google Authenticator, Microsoft Authenticator) or hardware security keys (e.g., YubiKey), which are not tied to the phone number directly and require physical possession of the device.
4. Limited Context and Granularity:
A phone number alone provides no context about the individual's current mental state, intent, or the specific context of their online activity.
It cannot distinguish between a legitimate user and someone who has illicitly gained control of their number.
5. Challenges in Detection for Fraud Prevention:
Difficulty in Real-time Verification: While services can check if a number is active, its type (mobile, landline, VoIP), or if it has been recently ported, accurately and instantly verifying that the current user of the number is its true owner remains a challenge.
Evolving Tactics: Fraudsters constantly adapt their methods, making it difficult for phone number-based security measures to keep pace.
6. Operational and Cost Burdens for Businesses:
Due to the limitations, businesses often need to implement multiple layers of authentication beyond just phone number verification, which adds complexity and cost to their operations and can impact customer experience.
In Bangladesh, where mobile penetration is extremely high and many digital services (e.g., Mobile Financial Services like bKash, Nagad) are heavily reliant on phone numbers and SMS OTPs, the vulnerabilities associated with phone number-based identity are particularly pronounced. The integration of NID with SIM registration was a step towards stronger identity, but persistent issues like the NID server glitches and potential for fraudulent SIM activation highlight that even with such measures, phone numbers are a fragile foundation for comprehensive identity verification. Relying solely on them is a significant risk for both individuals and service providers.