What is cryptojacking?

Cryptojacking is when someone secretly uses your device's processing power to mine cryptocurrency for themselves. The victim pays for the electricity, wear and slowdown, while the attacker keeps the coins. It targets home computers and phones as well as company servers and cloud accounts.

What is crypto mining malware?

Crypto mining is computing work that earns new coins. Mining software is legal to run on your own machine. It becomes malware when it is installed without the owner's consent.

CISA, the US Cybersecurity and Infrastructure Security Agency, says attackers install miners by exploiting flaws in web pages, software and operating systems. It lists weaponized mobile apps, botnets, social media, hijacked Wi-Fi hotspots and vulnerable servers as other routes. Unlike browser mining, this kind can keep running after you leave the place you caught it.

Businesses are big targets. Microsoft said in 2023 that attackers who took over cloud accounts, usually ones without multi-factor authentication, ran up more than $300,000 in computing fees for some victims. A 2021 Google report found that 86% of 50 recently compromised Google Cloud accounts were used to mine crypto, often within about 22 seconds of the break-in.

What is browser cryptojacking?

In browser cryptojacking, mining code is added to a website. When you visit, scripts in the page use your processor to mine while the tab stays open. CISA says this type usually stops when you leave the site.

Some browsers try to block it. Mozilla says Firefox's Enhanced Tracking Protection blocks cryptominers in both its Standard and Strict settings.

How can you tell if your computer is mining crypto?

CISA lists these warning signs:

• processor use that stays unusually high, even when you are not doing much
• a device that runs noticeably slower
• slower network performance
• overheating, which in serious cases can damage hardware

Mining depends on doing the same calculations over and over, so it leaves a pattern. Microsoft says its Defender security software can spot that pattern at the processor level, even when the miner tries to hide. Other security tools look for connections to mining pools.

How do you protect against cryptojacking?

CISA's advice is mostly basic hygiene. Keep software and operating systems updated, use antivirus software, and avoid downloads from untrusted sites. Use long, unique passwords and change default ones. Limit administrator rights and remove software you do not use.

For cloud accounts, Microsoft stresses multi-factor authentication and watching for unexpected requests to add computing capacity. Many of the same habits also guard against phishing and wallet drainers, and against fake apps of the kind described in do crypto mining apps work.

Threats and tools change often. Check official security guidance or a qualified professional for your own setup.