6 Signs Your Smartphone Has Been Compromised

Can you confidently say your phone hasn’t been compromised? Whether we like it or not, today’s generation has gotten used to the idea that smartphones are tracked by governments, hackers, employers, exes, journalists, and more. These groups can listen to your calls, read and send your messages and emails, or even alter information within your device. In this article, we’ll look at six signs that someone else may have access to your phone.

1. Constant Battery Issues

Before iOS and Android became popular, battery problems were one of the main signs a phone had been compromised. Even with modern smartphones, an overheating battery is still a concern.

You’ve probably experienced your phone getting hot and maybe even asked about it at a store. Most of the time, you’re told that a warm battery is normal for smartphones. For example, Apple only gets concerned about overheating if the device starts shutting down.

Why might your smartphone overheat? It could be due to too many running apps or constant content consumption from various sources. However, these reasons alone usually won’t seriously harm your device.

Still, a hot battery can also indicate your phone has been compromised, especially if spyware is running in the background. Pay special attention if your phone can’t hold a charge at all.

Monitor your phone and see how apps affect the battery. If an app is draining your battery even when you rarely use it, investigate further. On the other hand, older phones naturally hold less charge, so consider other causes before suspecting spyware—like sun exposure or too many open apps. Is your phone’s body hot? Are there Bluetooth devices connected?

Overheating can be a sign of malware, so watch for other symptoms discussed below.

2. Increased Mobile Data Usage

Keeping an eye on your phone bill can help you save money and spot spyware.

Countless apps use a lot of data, especially if you avoid free Wi-Fi for security reasons. It’s even worse if your kids use your device when you’re not home. In general, track how much data you use each month.

If your data usage suddenly spikes compared to your average, find out why. Someone could be collecting and sending your information to an external source, not just over your home Wi-Fi, but anywhere you go.

3. Annoying Ads and Unfamiliar Apps

You might think you know your phone inside and out (or maybe not so well) and forget about half the apps you’ve installed.

However, it’s crucial to know exactly what’s on your phone, especially apps running in the background. If you find apps you didn’t install, immediately check for malware.

One of the most notorious mobile malware programs is Hummer. In early 2016, this trojan infected about 1.4 million devices per day, first appearing in 2014, mainly in India, Russia, and the Philippines.

It’s estimated that if the creators (likely in China) earned just 50 cents per infection, they could make over $500,000 in 24 hours.

Once on a victim’s device, Hummer bombarded users with intrusive ads. The malware doesn’t always try to hide itself. After installation, Hummer attempts to gain superuser rights, allowing it to download all sorts of content and making removal extremely difficult—even a factory reset might not help.

This malware can generate tons of ad traffic, significantly increasing your data usage.

4. General Performance Issues

It’s natural for devices to slow down as they handle more data.

The HummingBad malware is similar to Hummer. Around 10 million people fell victim to this trojan, which infects devices when users accidentally download malicious apps—like fake versions of YouTube or WhatsApp, which can still be found in app stores.

Cybercriminals made about $300,000 a month with HummingBad, peaking in 2016, though the malware has seen a resurgence since then.

HummingBad also tries to gain superuser rights and sometimes prompts you to download fake system updates to gain full control over your activity. You’ll start seeing pop-up ads, and all your information is sent to a server controlled by the Chinese hacker group Yingmob. In addition to so-called “click fraud,” HummingBad can intercept all your messages.

If all your data is being intercepted, your device will slow down. At first glance, it might seem like your phone is just getting old.

This issue isn’t limited to HummingBad. Performance problems can occur no matter what method attackers use to control your phone.

Of course, legitimate apps can also use a lot of resources, but not enough to seriously affect your device’s responsiveness.

You can check which apps use the most memory. On iOS, go to Settings > General > iPhone Storage. On Android, the list of running apps is in Developer Options. Apps like Photos or Music may be at the top. Use this to spot resource-hungry or suspicious apps.

5. Strange Texts and Messages

You might already be ignoring signs of eavesdropping or surveillance.

For example, what seems like spam, a wrong number, or a random annoyance could actually be a red flag.

Weird SMS messages with random numbers, letters, or symbols might seem odd but easy to overlook. Don’t ignore these signs.

The most likely cause is a bug in the malware used by cybercriminals. If installed incorrectly, you might see coded messages in your inbox that go unnoticed. These random data strings could be instructions sent from a hacker’s server to the malicious app, or the app might be trying to contact its creator.

Another example: if family or friends say you’re sending strange messages or emails, your phone is probably compromised and being used to infect others.

In general, monitor any suspicious activity: message threads, social media profiles, sent and outbox folders. If you can’t remember sending a message, immediately do a thorough malware scan of your device.

6. Websites Look Different

This scam is more sophisticated, but extra vigilance can protect you.

It might seem like everyone knows how scammers operate, but incidents still happen. We forget advice and make the same mistakes—like clicking a malicious link in a message or email, which can cost you a lot of money.

You might not even be redirected to a malicious site. If malware is installed on your phone, it can alter the appearance of websites you visit regularly.

In this case, the malware acts as a proxy server, controlling communication between you and the site, showing you a fake page or simply recording everything you type. Even private browsing mode won’t help.

The problem arises when you use sites that require personal information: passwords, credit cards, and other financial or personal data—valuable currency on the Dark Web. Pay special attention to payment sites (like PayPal) and mobile or online banking.

Changes on fake sites can be tiny, like a few pixels in a logo. Even if you notice something odd, you might think the site is just testing a new interface. Compare the mobile version of a site to what you see on your computer, but remember that responsive pages will look a bit different.

Conclusion

Don’t become overly paranoid. Most of us won’t be victims of mobile phone surveillance. Still, it’s wise to take some security precautions.

Only download apps from official stores to reduce the risk of malware. Apple and Google check apps before making them available to the public. Also, pay attention to the signs described in this article.