How To Secure a Phone Number From Hackers

Today, most people have their phone numbers tied to essential functions such as 2FA account recovery, authentication, and identity verification, which makes them a high-value target for hackers. When compromised, a phone number can become a gateway to sensitive accounts and personal information.

In practice, a secure phone number should be difficult to exploit or take over, but technically, no number is inherently secure. You have to rely on the right safeguards and digital habits, as well as use a secure carrier network to limit attack vectors.

This guide explains how to secure a phone number, avoid common mistakes, and reduce the risk of unauthorized access.

What Is a Secure Phone Number?

A phone number’s security depends on how it is managed. A secure phone number is the result of security measures, from carrier-level protections to user-controlled safeguards, that reduce the risk of unauthorized access, interception, or takeover.

In practice, a secure phone number is typically built on three pillars:

When security weaknesses exist at the carrier, account or user level, you’re looking at vulnerabilities that hackers can exploit.

Common Vulnerabilities Associated With Phone Numbers

Attacks via phone numbers, such as SMS phishing (smishing) and robocalls, are getting fairly common. In 2024 alone, smishing resulted in $470 million in financial losses in the U.S.

Phishing scams involve texts and messages that often appear to come from trusted sources. They can trick recipients into downloading harmful software or sharing sensitive information, leading to unauthorized transactions, identity theft, or further compromise. These attacks are getting even more complicated with the use of AI for voice phishing (vishing), making it easy to impersonate trusted friends and family members.

On the other hand, if you’re using a phone number, you also inherit the network-level vulnerabilities of your carrier. The gaps can be infrastructure-focused or rely on bypassing or manipulating telecom security processes, such as:

• SIM swapping: Attackers impersonate the number owner and convince the carrier to transfer the number to a new SIM, gaining control over verification codes, calls, and messages.
• Account takeover: Using data obtained through the dark web, phishing, or hacking, attackers can take over online accounts linked to your phone number, change passwords or personal information, and make unauthorized transactions or transfers.
• Port-out fraud: Attackers fraudulently transfer a phone number to another carrier, allowing them to intercept phone calls and SMS messages, access verification codes, break into financial and social media accounts, and impersonate the victim to commit theft or other malicious actions.

How To Secure Your Phone Number: 5 Recommended Actions

Here are five main strategies for securing your phone number:

1. Reduce phone number exposure
2. Use a secondary phone number
3. Protect against SIM swaps and account takeover
4. Monitor accounts for suspicious activity
5. Use encrypted messaging and calling services

1. Reduce Phone Number Exposure

Using your phone number as the main identifier across multiple services, including banking and social media accounts, expands your attack surface. While it may be convenient, linking a single number to numerous accounts can increase the potential impact of a compromise and make it easier for hackers to target connected services.

Whenever possible, reconsider whether sharing your number is truly necessary for a service or if alternative verification methods are available, such as email-based verifications, authenticator apps, or security key-based logins.

When creating an account that requires a phone number, it helps to:

• Use a unique, strong password
• Answer security questions strategically instead of truthfully, avoiding details that could be uncovered through social engineering
• Prefer 2FA via authenticator apps or physical security keys whenever available

Finally, don’t link or publicly display your phone number on social media, and if your data is already listed in data broker databases, request removal where possible. You can also use apps like DeleteMe and Incogni to automate the opt-out process.

2. Use a Secondary Phone Number

Using a secondary phone number is a great way to reduce the exposure of your primary number.

Secondary phone numbers, used alongside your primary line, can be assigned to lower-trust signups. This way, if the secondary number is compromised, your primary line and connected services aren’t impacted. They can be useful for temporary subscriptions that need verification codes, online interactions, and even travel activities.

A common option for a secondary line is a prepaid SIM, which can be both disposable or for long-term use. It can support SMS-based authentication, but may still exposed be to the same carrier-level vulnerabilities and data-collection practices as any traditional mobile service.

A more convenient alternative is to use an eSIM as a secondary number. It’s a fully digital option that can circumvent common network threats and eliminate the need for a physical SIM card. However, eSIM security depends on the provider, and not all services offer the same level of protection or functionality.

Choosing a privacy-first carrier like Cape can make using secondary phone number more practical for everyday use. Rather than relying on burner numbers with limited functionality, users get two dedicated secondary lines for signups, travel, work and lower-trust online services.

3. Protect Against SIM Swaps and Account Takeover

One of the more effective protections against SIM swaps and port-out attacks is enabling SIM or port-out protection through a carrier PIN or password. Many major telecom providers, including AT&T, Verizon, and T-Mobile, allow users to set up a SIM or port-out lock secured with a PIN or password. While protection is enabled, attempts to transfer a phone number will succeed only if the user provides the correct credentials or the transfer is blocked otherwise.

Some providers also offer additional safeguards. For example, Verizon offers a Number Lock feature that lets you lock your lines and prevent access to your accounts. Once enabled, only the account holder or an authorized manager can disable this protection.

However, these measures are not foolproof. In cases of impersonation, social engineering, or internal threats such as employee bribery, attackers may still bypass protections through manipulation and impersonation tactics. Data breaches, which are quite common among leading telcos, can further increase this risk.

4. Monitor Accounts for Suspicious Activity

Monitoring your accounts for suspicious activity isn’t limited to phone-number defenses; it's part of broader mobile security hygiene. It can help reduce the impact of phone-number-related attacks by surfacing unrecognized login attempts, transitions, or account recovery notifications.

By detecting unauthorized activity early, you can respond quickly by changing passwords, securing accounts, and limiting further access.

A sudden loss of service or signal can also indicate a SIM-swapping attempt, especially if it occurs in an area with normally stable coverage and the device fails to reconnect after a restart. In such cases, it is important to act promptly and follow these steps:

1. Contact the mobile carrier and report suspicious activity so they can review recent account activity
2. Change passwords for any accounts that may be affected, especially those linked to SMS-based 2FA authentication
3. Request or enable port-out protection to reduce the risk of further unauthorized transfers

5. Use Encrypted Messaging and Calling Services

Many users turn to alternative communication channels, especially for sensitive conversations, to avoid the baseline security limitations of legacy telco systems. These alternatives, including WhatsApp and Signal, often use end-to-end encryption (E2EE) as a key safeguard, ensuring that messages are encrypted and accessible only to the conversation participants.

While regular SMS messages pass through the cellular network in a readable, unencrypted form—meaning that mobile carriers, authorities, or anyone who intercepts them may be able to access the content—E2EE works differently. It encrypts message content, making it unreadable to third parties. Messages are encrypted and decrypted using cryptographic keys that exist on the participants' devices.

This approach also extends to voice communication through Voice over Internet Protocol (VoIP) apps. Services such as Google Voice, Hushed, and TextNow provide internet-based phone numbers that reduce reliance on traditional phone networks and, like secondary phone numbers, limit exposure of your primary number. However, VoIP services may come with tradeoffs, including limited messaging capabilities, internet dependency, varying levels of encryption, and compatibility issues with some platforms or verification systems.

How To Get a Secure Phone Number: Why Provider Choice Matters

A phone number is only as secure as the carrier supporting it. If you’re getting a new number, consider the carrier’s security features, SIM swap protections, account recovery processes, and data collection practices. The problem with major telco networks is that they rely on outdated infrastructure and processes that weren’t designed for today’s threat landscape. As a result, there are limitations to how much they can protect you—and this is evident if you look at the breadth and frequency of recent telco data breaches.

If you want a more secure option, switch to a privacy-focused provider such as Cape. We use our own eSIMs and software-based mobile core that help us sidestep the vulnerabilities of legacy infrastructure.

Here are the main features of a secure eSIM-based phone number from Cape:

Meet Cape: The Secure Carrier Designed for Today’s Threats

We share the most intimate details of our everyday lives with our cell phones. In order to stay connected, our cell phones share that information with local cell networks, and in turn, those cell networks share our data with each other.

While this system is what makes connectivity possible, it was also built with interoperability as its priority, rather than security. The global cell network is vulnerable to a number of threats, as seen through headlines about major carrier data breaches we see time and time again. When major carriers aren’t losing our sensitive personal data in breaches and hacks, they’re actively selling it to ad networks, data brokers, and third parties.

At Cape, we believe that privacy and security shouldn’t have to be sacrificed for connectivity. That’s why we built our service with privacy principles and security features at its core, including:

1. Minimal Data Collection

Cape eliminates the risk of your sensitive data falling into the wrong hands by not even asking for it. When you make your Cape account, we don’t ask for your name, address, or SSN. We only collect the information that’s necessary to provide the service, and we retain it for the least amount of time possible.

2. SIM Swap Protection

During account creation, you receive a unique 24-word phrase that generates a private key tied to your phone number. This pass phrase is required to move your number to a new device or carrier. Nobody else, not even us at Cape, has access to the phrase, meaning there’s absolutely no way for bad actors to transfer your number to their device, effectively nullifying the possibility of SIM swapping.

3. Disappearing Call Logs

Your phone stores an incredible amount of data, which can be accessed through call and text records. Most mobile carriers store your call and text metadata for years, which can easily fall into the wrong hands.

Cape is built to forget, meaning we delete Call Data Records (CDRs) after just 1 day, ensuring nobody can see who you texted or called, track where the communication took place, or access the sensitive information within CDRs.

4. Identifier Rotation

All SIM cards are accompanied by International Mobile Subscriber IDs (IMSI). These function as unique identifiers devices use to register with cellular networks. Traditional telcos assign fixed IMSIs to user accounts, meaning the carriers, advertisers, hackers, and other bad actors can exploit them to identify and track your device.

Cape patches this security hole by allowing you to automatically rotate your IMSI every 24 hours. In practice, this means you appear as a different subscriber every day, making it much more difficult for anyone to identify your device or track your movements.

5. Secondary Numbers

Are you tired of spam messages from brands, phone call surveys, and scammers trying to trick you into sharing sensitive information over the phone? The reason why most people are exposed to these nuisances is that we are often required to share our phone numbers with retailers, websites, apps, and service providers.

While messages and phone calls can be annoying, what’s worse is that your number can easily become a target for data brokers and bad actors. That’s why many people turn to VoIP numbers as secondary lines. VoIPs are a decent option, but they don’t fully solve the issue—they are not encrypted, you can’t use them for 2FA, and they’re an additional cost each month.

When you sign up for Cape, you get two free additional SMS/MMS lines that are middle-to-end encrypted. This allows you to use Secondary Numbers for online shopping, signing up for services and discounts, and receiving secure OTPs, while your primary phone number is reserved for friends and family.

6. Network Lock

Traditional cellular networks were designed for interoperability, not security. Outdated and legacy network protocols like SS7 have vulnerabilities that allow attackers to hack in and track your location, intercept your calls and texts, and steal sensitive information.

Cape’s Network Lock uses a proprietary signaling proxy to verify that your device’s physical location matches the network it’s trying to attach to. If anything looks suspicious, like a mismatched location, we block the connection.

7. Encrypted Voicemail

Voicemails can reveal more than you think, from personal messages to authentication codes, yet most voicemail systems are outdated and unencrypted.

Cape encrypts your voicemails so that only you can access them.

8. Secure Global Roaming

To access phone service while traveling abroad, your phone typically needs to connect to local telecom providers. The trouble is, there’s no guarantee all networks are secure, and not every government treats privacy the same.

Cape doesn’t leave anything to chance. We let you route traffic through our U.S.-based mobile core, so you can safely use international data roaming without exposing your identity or sharing sensitive data or communications with foreign carriers.

With Cape, you get up to 15 GB per month of international roaming, included in your monthly plan.

Get Started With Cape Today

If you’re ready to make a switch from legacy telcos to America's privacy-first mobile carrier, visit cape.co/get-cape.

In addition to all the features listed above, you can further enhance your privacy and security with Proton. Our partnership with this technology leader allows you to get Proton Unlimited or Proton VPN Plus for only $1 for the first six months.