What is cryptojacking?
Cryptojacking is when someone secretly uses your computer, phone, or server to mine cryptocurrency without your permission. Mining uses computing power to help run a cryptocurrency network and earn rewards—but with cryptojacking, someone else gets the rewards while you pay through electricity use, slower performance, and extra wear on your device.
What makes it cryptojacking?
The key issue is your informed permission. If you knowingly choose to run a miner on your own device, that is not cryptojacking. If a website, app, or attacker starts mining without clearly telling you and getting your agreement, it is.
Cryptojacking can happen in several ways:
- A website runs hidden mining code while a page is open.
- A malicious app or browser extension installs a miner.
- An attacker breaks into a server and runs mining software.
- Someone steals access to your cloud account and rents computing power at your expense.
Monero sometimes appears in these attacks because its mining method, called RandomX, favors ordinary computer processors, or CPUs. That does not make Monero itself malicious. The abuse is using someone else’s resources without permission.
What you might notice
A hidden miner competes with your normal apps for computing power. You might notice:
- Fans running loudly when you are doing very little.
- A device getting unusually hot.
- Sluggish apps or a browser that feels unresponsive.
- Faster battery drain.
- Unexpected electricity use or cloud-computing charges.
These signs are clues, not proof. Video calls, games, software updates, and other legitimate tasks can cause similar symptoms. Some hidden miners also limit their activity to avoid attracting attention.
You can check your operating system’s activity monitor, such as Task Manager on Windows or Activity Monitor on macOS, to see which apps are using the processor. An unfamiliar process deserves investigation, but do not delete system files just because their names look strange.
What to do if you suspect it
If the problem begins on a particular website, close that tab. A miner running only inside that page will normally stop when the page closes. If heavy processor use continues, another tab, extension, or installed program may be responsible.
Next, take a few practical steps:
- Update your browser, operating system, and security software.
- Run a scan with a trusted security tool.
- Review browser extensions and remove ones you do not recognize or need.
- Uninstall suspicious apps using your device’s normal uninstall process.
Avoid pop-ups offering a “mining cleaner” or asking you to disable antivirus protection. They may be another scam.
If a work device is affected, contact your IT team. If your cloud account shows unexplained activity, contact the provider promptly, secure the account, and review running services and billing. Removing a miner alone may not fix the access problem that allowed it in.
The bottom line
Cryptojacking is mining without your informed permission, whether it happens in a browser or through installed software. Legitimate mining should clearly explain what will run, what resources it uses, who receives the rewards, and how you can stop it.
Unauthorized mining can violate computer-misuse laws and service terms; the exact rules depend on where you live. If you need legal advice after an incident, check local rules or speak with a qualified professional.
