Cryptojacking, Explained

Your device is slow. The fan won’t stop whirring. You didn’t install anything new, but your battery’s draining faster than ever.

All of these may mean that you are an unfortunate victim of cryptojacking.

Cryptojacking is a silent attack that hijacks your system’s resources to mine cryptocurrency—digital money created through heavy computing—without your knowledge. Unlike ransomware or data theft, this attack operates in the shadows, quietly turning your device into a money-making machine for cybercriminals.

Don’t worry, though—cryptojacking is preventable, and the signs are easy to catch once you know what to look for.

Want to know more? Read on as we discuss:

• How cryptojacking actually works

• Common infection methods

• Warning signs to watch for

• Tools and habits to prevent it

At the end of this article, you’ll know how to detect and defend against cryptojacking before it drains your systems—and your wallet.

How cryptojacking works

A device gets cryptojacked when it’s exposed to malicious code that, as mentioned above, forces it to mine cryptocurrency in the background. There are three ways you can experience cryptojacking:

• Malicious websites: Some sites run crypto-mining scripts directly in your browser. You don’t even have to download anything. Just visiting the site or opening a page is enough for the script to start using your CPU.

• Infected software: You might unknowingly install a program or extension that contains hidden mining malware. Sadly, it can stay undetected for weeks.

• Compromised cloud accounts: For businesses, cloud accounts are a major target. Attackers look for weak login credentials or unsecured access points. Once inside, they exploit the organization’s cloud infrastructure for large-scale crypto mining.

At first glance, cryptojacking may seem harmless. It doesn’t steal your data or lock your files. But it silently wears down your device, causing it to lag, overheat, or break down faster than usual. It also drives up power costs, especially on cloud platforms where you’re charged for compute time.

Worse, the same weaknesses that let cryptojacking in can be exploited again. Once attackers gain access, they can install the aforementioned ransomware (which locks your data until you pay) or spyware (which secretly monitors your activity) with minimal resistance.

Signs of cryptojacking

One of the most frustrating parts about cryptojacking is how quietly it operates. It doesn’t show pop-ups, alerts, or warnings. But it does leave traces. Here are some common signs that your device may have been hijacked.

Constant fan noise or device overheating

Cryptojacking scripts force your CPU to run at high capacity around the clock, generating excessive heat. This triggers the fan to keep cooling the system, sometimes nonstop. If your laptop or desktop fan is unusually loud even during simple tasks like browsing or emailing, it’s a potential red flag.

This isn’t limited to computers. On smartphones, the device may feel warm to the touch even when idle. That kind of unexplained heat is often a sign that something is quietly running in the background.

Lagging performance

Cryptomining consumes a large share of your device’s processing power. This often leads to noticeable slowdowns. Applications take longer to load, your browser might freeze, or multitasking becomes sluggish. If basic tasks feel unusually heavy on your machine, it’s worth checking for unexplained background activity.

Battery draining quickly

For laptops and mobile devices, battery life is another telltale sign. If your device suddenly needs charging more often or dies unexpectedly fast—even when you’re doing light tasks—there may be a hidden process running in the background. Mining operations are resource-intensive and will drain your battery much faster than normal.

Unusual CPU usage

On Windows or macOS, you can check your CPU usage via Task Manager or Activity Monitor. If your CPU is running at high capacity—even when no major apps are open—this could be a sign of a cryptojacking script or process. Often, these malicious scripts disguise themselves as legitimate system processes, so a sudden spike in usage deserves closer inspection.

High cloud service consumption (for businesses)

For organisations using cloud platforms like Google Cloud or AWS, cryptojacking often appears as a sudden spike in resource consumption. Since, as mentioned above, cloud services are billed based on compute time, storage, and data transfer, any hidden mining activity directly increases costs. You might see unusually high CPU or GPU usage, longer virtual machine runtimes, or unexpected scaling of cloud instances, even though business workloads haven’t changed. In many cases, these anomalies are the first signs that your cloud environment has been compromised. 

Note that most of these signs on their own could be caused by other issues, like aging hardware or buggy software. But if several of them show up at once—especially without a clear cause—it’s time to dig deeper. Spotting the signs early is your best chance at stopping cryptojacking before it causes long-term damage.

How to prevent cryptojacking

Stopping cryptojacking before it starts is far easier than dealing with its effects. Here are five practical ways to reduce your risk and protect your systems:

• Use anti-mining browser extensions: As mentioned earlier, many cryptojacking attacks begin through the browser. Tools like NoMiner or MinerBlock can block known mining scripts from running on websites. These lightweight extensions prevent background crypto mining without affecting your regular browsing experience.

• Keep your OS, browser, and plugins updated: Outdated software often contains security gaps that cryptojackers exploit. Make sure your operating system, browsers, and browser plugins are always up to date with the latest patches. Enabling automatic updates can help reduce the risk of missing critical fixes.

• Avoid sketchy downloads or email attachments: File-based cryptojacking usually spreads through suspicious apps, cracked software, or phishing emails. Never download software from unverified sources, and avoid opening unexpected attachments, especially if the email seems off or overly urgent. When in doubt, don’t click.

• Use security tools designed to protect your device: Install a reliable antivirus or anti-malware program that offers real-time protection and automatic threat detection. These tools can block cryptojacking scripts before they run. Many now include specific features to detect crypto-mining activity. Look for trusted names like Bitdefender or Malwarebytes.

• Monitor CPU usage regularly: Unusual spikes in CPU activity—especially when your device is idle—can be an early sign of cryptojacking. Use built-in tools like the above-mentioned Task Manager (Windows) or Activity Monitor (macOS) to keep an eye on usage. For businesses, keep track of usage across your cloud services. Several platforms offer monitoring dashboards that show compute activity in real time.

Conclusion

Cryptojacking doesn’t steal your files or hold your data hostage—but it still takes a toll. It slows down your device, wastes energy, drives up costs, and leaves you open to more serious attacks. Its danger lies in how easily it slips by unnoticed.

If your device overheats, your battery drains faster than usual, or your cloud bill suddenly spikes, it’s worth taking a closer look. Those subtle signs could point to something running in the background that shouldn’t be there.

Stay alert. The sooner you detect cryptojacking, the easier it is to stop. In this case, awareness really is protection.