The SIM card inside your phone allows you to connect to cellular networks and use mobile data, but it comes with some major privacy tradeoffs. In this article, we’ll dive into how SIM cards can covertly track your location, monitor your internet activity, and bypass VPN encryption. We’ll also explore alternative options like using a mobile hotspot for connectivity instead of a phone SIM card.
How SIM Cards Track Your Every Move
As you move around with your phone, the SIM card inside maintains connectivity by communicating with cell towers in range. Your phone pings these towers constantly, allowing carriers to log the exact time and signal strength each time your device connects to a new tower. By aggregating this location data over time, cell providers can pinpoint your location and movements throughout the day.
This real-time location tracking data gets associated with your phone’s unique IMSI number, essentially creating a personalized map of your daily habits and routines. Cell providers use this granular location data for advertising purposes, and also sell it to third parties. Law enforcement frequently purchases location records from carriers as well.
So if you’re concerned about location privacy, just know that whenever your SIM card is active, your cell provider has a precise record of where your phone has been.
Hidden Communication Between SIM Cards and Networks
Another privacy consideration with SIM cards is the hidden communication that can occur between the card and cell networks without your knowledge.
Smartphones actually contain three separate computing components:
- The main application processor that runs your phone’s operating system and apps
- The baseband processor that handles all cellular network communications
- The SIM card itself, which has its own independent computing capabilities
The baseband processor and the SIM card can exchange data and commands autonomously, without any visibility on the main application processor of your phone. This means your SIM card has the ability to initiate certain tasks like sending SMS messages or starting a data connection without you explicitly triggering those actions.
The contents of the communication between SIMs and baseband processors are encrypted, so there’s no way to know exactly what data is being exchanged. Given the privacy sensitivities of our mobile devices today, the opaque nature of this background communication should give us pause.
Risk of VPN Bypass
A third issue to consider with SIM cards is the risk of “split tunneling,” where some traffic from your phone bypasses the VPN tunnel.
Many people use VPNs on their phones to encrypt traffic and mask their IP address. But research from Mysk shows that numerous Apple and Android apps actually ignore the VPN and make direct external connections. This traffic gets exposed to the open internet instead of traveling through the VPN tunnel first.
For example, on iPhones the Stocks, Health, Wallet, Messages, and FindMy apps were observed communicating directly with Apple servers despite an active VPN connection on the device.
This vpn bypass occurs because the phone’s operating system controls both device apps and the VPN client. If the OS wants to allow traffic outside the vpn for certain system services, it can.
So with a SIM card in your phone, you lose visibility and control into what traffic gets tunneled through the VPN versus what bypasses it completely.
Alternatives for Mobile Connectivity & Privacy
Given the location tracking, hidden communication channels, and VPN bypass risks, you may want to consider alternatives to using a SIM card in your phone.
The most common question is: without a SIM card, how do you get mobile internet connectivity?
The answer is you’d use Wi-Fi networks instead of cellular data from a SIM. As long as you can connect to a Wi-Fi network, your phone will function normally for calling, messaging, email, apps, etc. The only difference is that instead of having a “cell number” from your SIM provider, you’d use an internet-based VoIP number for calling and texting.
When you’re at home or work, just connect to those familiar Wi-Fi networks. But what about when you’re out and about? Here are two options:
Using Public Wi-Fi
Some people jump on public Wi-Fi networks when they need connectivity on the go. The privacy benefits of this approach are:
- You can keep your phone in airplane mode otherwise to stop leaking location data to cell towers
- Public Wi-Fi doesn’t require providing personal info, so you avoid disclosing your IMEI, IMSI, and other identifiers to cell networks
- Using a VPN over Wi-Fi adds a layer of encryption and anonymity vs cellular networks
The downside is that public Wi-Fi networks can have security risks, may be slow, and may not always be available when you need connectivity urgently.
Using a Mobile Hotspot
Another option is to use a separate mobile hotspot device that contains a SIM card providing LTE data connectivity. This gives you mobile internet access that you can connect your phone and other devices to via Wi-Fi or ethernet.
Here are some of the privacy advantages of using a hotspot instead of putting the SIM card directly in your phone:
- Siloing the SIM card into the hotspot means its baseband processor handles communication with cell towers rather than your phone’s baseband. This may reduce privacy risks from any hidden signaling occurring between SIMs and networks.
- A hotspot likely exposes less sensitive personal activity patterns to cell providers compared to a phone SIM card.
- You can run VPN clients on the hotspot itself to encrypt all traffic without risk of OS-level VPN bypass issues.
- Reduced location tracking since the hotspot can be turned off when not in use, unlike a SIM card that remains active in your phone at all times.
Hotspots from Calyx Institute offer added privacy benefits like anonymous purchase options and unlimited high-speed data on their network.
The main downside of using a hotspot is you have to carry around two devices instead of just your phone. But many people find the privacy tradeoff worthwhile.
Should You Use a SIM Card or Hotspot?
There are certainly advantages and disadvantages to removing your SIM card and using alternative connectivity options instead. Here are a few key considerations:
- Assessing your personal privacy priorities and concerns around location tracking, hidden SIM communication channels, VPN tunneling, etc.
- Evaluating if a hotspot provides sufficient mobile connectivity for your needs or if you depend heavily on always-on cellular data.
- Understanding the convenience tradeoffs – do you mind carrying an additional device or occasionally hunting for public Wi-Fi?
This won’t be the right setup for everyone, but exploring SIM-free options can provide greater visibility and control over your mobile connectivity, data usage, and device privacy.
Optimize Mobile Privacy However You Can
Whichever path you choose, there are steps you can take to boost privacy:
- Use a VPN to encrypt traffic whenever possible
- Limit app permissions to location/microphone/contacts access
- Turn off location services you don’t need
- Use airplane mode when feasible to limit tracking
- Avoid oversharing personal details and usage patterns with apps
- Use privacy-focused services like secure messaging apps and private search engines
With a few tweaks, you can start taking back control over your mobile privacy. Just remember, small steps in the right direction can still make a big difference.