Cryptojacking is a crime in which cyberattackers hijack someone’s device to mine cryptocurrency — and all without the victim even realizing it. By deploying malicious software or embedding hidden scripts in websites, they essentially siphon processing power, secretly collecting cryptocurrency for themselves while the compromised device does all the heavy lifting.
Cryptojacking Definition
Cryptojacking is the unauthorized use of someone else’s computer or device to mine for cryptocurrency without their consent.
Exploiting another person’s compute power enables these bad actors to solve the complex mathematical puzzles that are essential to earning cryptocurrency. These digital coins can then be traded for other cryptocurrency, or converted to traditional money. In the end, the perpetrator essentially gets free money while the victim’s device is left drained and compromised.
What Is Cryptojacking?
Cryptojacking is a type of cyberattack where hackers use a victim's computer or device to mine cryptocurrency without their consent. Typically, this involves infecting a device — whether it be a smartphone, desktop, laptop or network server — with malicious software. Or sometimes, hackers use mining scripts embedded into websites that activate when the victim visits the site. Specially designed to avoid detection, these programs run stealthily in the background, unbeknownst to the victim.
Unlike most other types of cyber attacks, cryptojacking scripts do not damage the victim’s device or data. They do, however, exploit the targeted device’s processing power, hindering its performance and potentially causing long-term damage. Slowed device performance, overheating batteries, system crashes and an unexpected spike in electricity costs are all signs of cryptojacking.
How Does Cryptojacking Work?
To access a victim’s processing power, a cryptojacker must first trick their way into a system. They can do this through various social engineering or technical exploitation schemes riddled with malicious links, including phishing emails, fake software updates, infected ads (or malvertisements) and compromised websites. Other routes include social media scams and luring victims to fake “free” updates and cryptocurrency sites.
Once clicked, a victim’s device is hijacked — either through host-based jacking, where the malicious software is downloaded, or browser-based jacking, where scripts run in the background of a website. Either way, these resource-sucking codes siphon processing power from a device’s CPU or GPU to mine for cryptocurrency. In some cases, the codes will embed themselves into a device’s RAM using memory-based attack. More advanced methods may employ malware with “worm” capabilities, allowing the attack to spread across a network and infect other connected devices.
The mining process continues as long as the device remains powered on. However, the malicious code vanishes once the victim leaves the website or reboots their device, making this cybercrime particularly difficult to detect and trace.
How to Detect and Prevent Cryptojacking
Detecting instances of cryptojacking once they’ve already begun can be quite challenging, as the process is often hidden or disguised as harmless. But there are some telltale signs, including:
- Your computer is overheating, causing its fan to run faster than usual.
- Your computer’s battery is draining faster than usual.
- Your computer is running abnormally slow or shutting down completely.
- Your electricity bill is unusually high.
If you suspect you’re a victim of cryptojacking, you can usually stop it by running a thorough scan of your antivirus software and removing any malicious browser extensions. But the absolute best way to deal with cryptojacking is to prevent it from happening in the first place. Here are some prevention tips:
- Only visit sites that are vetted as safe, and block sites that are known for cryptojacking.
- Do not click on suspicious links or visit suspicious websites.
- Use browser extensions that are specifically designed to block crypto mining.
- Block JavaScript while browsing, as this is a popular tool cryptojackers use to gain access to your device’s computing power. (Note: This may make some important features on the websites you visit unusable.)
- Use more privacy-focused ad blockers.
- Install the latest software updates and patches for your operating system and all your applications, particularly for web browsers, once they become available.
- Regularly monitor the resources on your computer, including its processing speed and power usage.
Types of Cryptojacking
There are three main types of cryptojacking: browser-based, host-based and memory-based hacking. Read more about each one below.
Browser-based Cryptojacking
Browser-based cryptojacking occurs when malicious scripts are embedded directly into a website, where it can mine in the background while the unsuspecting victim is visiting the site. This method is particularly effective, as it only requires a victim to click on a link — whether it’s a URL or advertisement — without downloading or installing any malware. The script runs in the browser, often slowing down a device’s performance and increasing energy consumption, then stops when the user closes the browser, making it harder to detect and trace.
Host-based Cryptojacking
With host-based cryptojacking, a victim is tricked into installing malicious software onto their device. Unlike browser-based cryptojacking, this attack persists until the malware is detected and removed, often degrading system performance and increasing power consumption over time. It typically spreads through phishing emails, malicious downloads or software vulnerabilities, making it a more invasive, lasting threat.
Memory-based Cryptojacking
Memory-based cryptojacking is a technique where malicious mining code runs directly in a device’s memory, or RAM, without having to be installed on the hard drive. Of the three cryptojacking types, this method is the most resource-draining, and it’s the hardest to detect, since the malware disappears once the system is rebooted.
Frequently Asked Questions
What are signs of cryptojacking?
Some tell-tale signs of cryptojacking include sluggish device performance, overheating batteries, system crashes and a sudden increase in electricity costs.
Is cryptojacking illegal?
Yes — cryptojacking is an illegal cybercrime. Unauthorized use of someone else’s computer, network or device is a privacy violation that’s punishable by fines or imprisonment.
How can you prevent cryptojacking?
Using reputable antivirus software, regularly updating software, enabling browser extensions that detect mining scripts and avoiding suspicious websites and links are a few cryptojacking prevention tactics. Also, keep an eye on your computer’s energy usage, as well as cloud-based compute and storage fees, in order to spot unusual activity.
