Cryptojacking: Why Is Your Fan Whirring and Your Computer Running Slowly for No Reason?

Have you ever been browsing the internet peacefully when, all of a sudden, your computer starts to "take off"? The fans are spinning at full speed, your laptop is burning up, and the mouse is moving jerkily. You check Task Manager and see that the CPU is at 100% usage, even though you’ve only opened a browser.

No, your computer hasn’t broken down. Most likely, you’ve fallen victim to a phenomenon called cryptojacking. In 2026, hackers aren’t just stealing data—they’re also stealing electricity and processing power. At Altanet Craiova, we help you identify the digital parasites that are draining your equipment.

What is Cryptojacking and how does it “steal” your processor?

Cryptojacking is the unauthorized use of someone’s computer (or phone) to mine cryptocurrencies (such as Monero). Hackers need immense computing power to generate virtual money, but they don’t want to pay for equipment and electricity. So they use your equipment.

There are two main ways they get to you:

• Via Browser (Web-based): You visit a shady website (for online movies or downloads) that hides a mining script. As long as you keep the page open, your processor works for the hacker. When you close the tab, it stops.
• Through Infection (Malware): You download an infected file that installs an "invisible" mining program. It runs in the background constantly, even when you’re not online, slowing down your entire system.

Clear signs that you’re being used as a “miner”

Unlike other viruses that remain hidden, cryptojacking has obvious physical effects on your device:

• Overheating: Components are constantly running at maximum capacity, leading to high temperatures. This can shorten the lifespan of your processor or graphics card.
• Fan noise: The cooling system is desperately trying to keep up, so the fans will sound like a vacuum cleaner.
• Electricity bill: If you have a powerful desktop system and are infected with persistent malware, you’ll notice an unexplained spike in electricity usage.

How do you stop unauthorized mining?

The good news is that you can defend yourself relatively easily if you know which tools to use:

• Install anti-mining extensions: In addition to the classic AdBlock, there are special extensions (such as No Coin or MinerBlock) that detect and block mining scripts in your browser.
• Use a good antivirus: Modern security solutions immediately detect if a process is trying to use 100% of the CPU for no reason and stop it.
• Check Task Manager: If your PC is running slowly, open Task Manager (Ctrl+Shift+Esc). If you see that your browser (Chrome/Edge) is using 80–90% of the CPU, close the tabs one by one until the usage drops. This is how you identify the offending site.

To better understand how these attacks evolve and how to protect yourself, you can consult the comprehensive guide provided by Malwarebytes on Cryptojacking.

Conclusion

Your computer is your property. Don’t let anyone use it as a “digital slave” to make money. If you hear the fans running at full speed without you playing games or editing video, it’s time for a check.

Is your computer running slowly and do you suspect an infection? Our team can perform a complete virus removal and hardware optimization. Check out our list of IT services and visit our contact page to bring your devices back to life.

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This article is part of Altanet’s educational series on digital security. Want to know what other risks you’re facing this year? See the complete list of cyber threats for 2026.