What Is Cryptojacking? Definition, Signs, and Prevention

Cryptojacking is a type of cyberattack where hackers secretly use your device’s computing power to mine cryptocurrency. Unlike ransomware or data breaches, it doesn’t steal your data, instead, it slows down your system, drains battery life, and increases energy usage, often without you noticing.

This threat has become increasingly common, especially as cryptocurrency values rise. Attackers embed mining scripts in websites, apps, or email links, making it easy to target individuals and businesses alike.

In this blog, we’ll explain how cryptojacking works, why it’s a growing concern, and howyou can reduce the risk.

What Is Cryptojacking?

Cryptojacking meaning the unauthorized use of someone’s device, such as a computer, smartphone, or server, to mine cryptocurrency. Instead of breaking into financial accounts or stealing personal data, cybercriminals hijack a system’s processing power to perform complex calculations that generate digital currency. This process runs silently in the background, often without the user’s knowledge.

The primary target of cryptojacking is computing resources. Hackers aim to exploit as many devices as possible to maximize mining output, often spreading the attack across thousands of compromised machines. This not only slows down devices but also leads to higher electricity consumption, reduced hardware lifespan, and degraded overall performance.

Unlike traditional cyberattacks, cryptojacking typically doesn’t involve ransomware or data theft, which makes it harder to detect. Victims may only notice that their systems are running slower or that their fan is constantly spinning at high speed.

Types of Cryptojacking

Cryptojacking scripts are usually delivered in two ways:

1.   Browser-Based Cryptojacking

Browser-based cryptojacking doesn’t require malware to be installed on the victim’s system. Instead, attackers embed mining scripts, usually written in JavaScript, into websites, online ads, or browser extensions. Once a user visits the compromised site, the script automatically begins mining cryptocurrency using the device’s CPU or GPU.

Exploiting JavaScript (e.g., Coinhive scripts)

Coinhive, now defunct, was one of the first widely used services that allowed websites to run JavaScript-based Monero mining directly in browsers. While some sites used it with user consent as an alternative to ads, it was more commonly abused without permission. Despite Coinhive shutting down, clones and similar scripts still circulate across the web, continuing to exploit unsuspecting users.

Drive-by Mining Attacks

Drive-by cryptojacking involves malicious mining scripts being loaded instantly when a user visits a compromised website. No clicks or downloads are necessary. The script executes in the browser tab and runs as long as the site remains open, mining cryptocurrency in real time. Some scripts even remain active after the tab is closed, through pop-unders or hidden windows.

2.   Malware-Based Cryptojacking

Malware-based cryptojacking is a more persistent and stealthy form of attack. It involves infecting a user’s system with malicious software that installs a background miner, which continuously uses system resources until removed.

Infected Downloads & Phishing

This form of cryptojacking often starts with social engineering, phishing emails, fake software updates, or trojanized apps. Once the user downloads and runs the file, the cryptojacking malware installs itself silently. Unlike browser-based scripts, these miners do not rely on user sessions and will continue mining even when the browser is closed.

Persistence Mechanisms (Rootkits, Backdoors)

Advanced cryptojacking malware employs persistence techniques to evade detection and ensure longevity. This includes using rootkits to hide mining processes, creating scheduled tasks that relaunch the miner if it’s stopped, or exploiting backdoors to reinstall the malware after removal. These tactics make it harder for users and antivirus tools to identify or remove the infection.

Signs of Cryptojacking

Cryptojacking is designed to be discreet, but it still leaves behind telltale signs. Since it hijacks your system’s processing power, the most noticeable symptoms are related to performance degradation and unusual system behavior. Being aware of these indicators can help you detect cryptojacking early and take corrective action.

Here are the most common signs to watch for:

1.   Unusually High CPU or GPU Usage

A sudden spike in CPU or GPU usage, especially when the device is idle or running basic applications, is a strong indicator of cryptojacking. You can monitor this using Task Manager (Windows), Activity Monitor (macOS), or system resource tools on Linux.

2.   Overheating Devices

Since cryptojacking forces your processor to run at high capacity, your device may become unusually hot. Constant fan noise or overheating when performing light tasks (like browsing or emailing) could suggest background mining activity.

3.   Reduced Battery Life

For mobile devices and laptops, cryptojacking can significantly drain battery life. If your device isn’t lasting as long as it used to, even with minimal usage, it might be unknowingly mining cryptocurrency.

4. Sluggish Performance

Cryptojacking consumes resources needed for other applications. You may notice lag, delayed responses, or frequent system freezes, particularly when switching between apps or opening new browser tabs.

5.   Increased Data Usage

Some mining scripts communicate with remote servers to send mined data or receive new instructions. If you notice unexplained spikes in data usage, especially on mobile networks, it might be related to a cryptojacking script running in the background.

6.   Unexpected Browser Behavior

If your browser feels slow, crashes often, or continues to run even after all tabs are closed, a cryptojacking script might be at play, especially if you’ve recently visited unknown or suspicious websites.

7.   Unknown Processes in Task Manager

Cryptojacking malware often runs under obscure or misleading process names. Regularly check your system’s running processes and investigate any unknown tasks consuming high CPU or memory resources.

Common Cryptojacking Attack Vectors

Cryptojacking attacks can be launched through various entry points, targeting both individuals and businesses. Understanding how attackers deliver mining scripts or malware is key to building strong defenses. Here are the most common attack vectors used in cryptojacking campaigns:

1.   Malicious Websites and Drive-by Downloads

Cybercriminals often compromise legitimate websites or create fake ones that host cryptojacking scripts. When users visit these sites, the scripts automatically run in the browser and begin mining cryptocurrency without needing user interaction, this is known as drive-by cryptojacking. In many cases, users are unaware that their system resources are being hijacked.

2.   Infected Software and Freeware

Attackers frequently bundle cryptojacking malware with pirated software, cracked applications, browser extensions, or free utilities. Once installed, these programs deploy background miners that continuously exploit the system’s CPU/GPU. Since these miners run silently, users may not realize their devices are compromised.

3.   Phishing Emails and Malicious Attachments

Phishing remains a popular method for distributing cryptojacking malware. Users receive emails that appear legitimate, often with urgent messages and clickable links or attachments. Once clicked or downloaded, a hidden miner is installed on the device. Unlike browser-based attacks, these miners persist until detected and removed.

4.   Compromised Content Management Systems (CMS)

Attackers can exploit vulnerabilities in CMS platforms like WordPress, Joomla, or Drupal to inject cryptojacking scripts into webpages. Visitors to the affected site unknowingly run the mining script in their browser, making CMS-based attacks an effective vector for mass infections.

5.   Cloud Infrastructure Exploitation

With the rise of cloud computing, cryptojackers have started targeting cloud servers and misconfigured instances. Once attackers gain access, usually through weak credentials or unpatched software, they deploy mining scripts that leverage the scalable computing power of the cloud, resulting in massive unauthorized crypto-mining operations and inflated billing for the account owner.

6.   Browser Extensions and Add-ons

Some browser extensions, especially those from unofficial sources, may include cryptojacking code. These extensions run with elevated permissions and can execute mining scripts each time the browser is launched or when specific sites are visited.

7. Supply Chain Attacks

Cryptojackers may compromise a third-party vendor or software dependency to insert mining scripts into legitimate software updates or development pipelines. Once distributed, these updates infect multiple systems, making supply chain attacks highly scalable and difficult to trace.

How to Detect Cryptojacking

Detecting cryptojacking can be challenging because attackers design these operations to remain stealthy. However, with the right tools and awareness, you can identify signs of unauthorized mining on your devices or network. Here are the most effective methods for detecting cryptojacking:

1. Monitor System Resource Usage

A sudden or sustained spike in CPU or GPU usage, especially when your device is idle or performing simple tasks, is one of the clearest signs of cryptojacking.

• On Windows, use Task Manager to identify processes consuming high resources.
• On macOS, use Activity Monitor.
• On Linux, use top or htop commands. If you spot unfamiliar processes using excessive CPU, investigate further.

2. Use Anti-Malware and Endpoint Protection Tools

Modern anti-malware software can detect known cryptojacking malware, browser-based mining scripts, and suspicious activity patterns. Choose a solution that includes behavior-based detection and real-time monitoring.

3. Analyze Browser Performance

Cryptojacking scripts often run within browsers, especially in drive-by attacks. If your browser becomes unusually slow, crashes frequently, or your fans spin up during simple browsing sessions, check for:

• Extensions you don’t remember installing.
• Tabs consuming excessive CPU (using Chrome Task Manager or browser dev tools).
• Persistent processes even after closing the browser.

4. Network Traffic Monitoring

Cryptojacking malware communicates with mining pools to send results and receive instructions. Use network monitoring tools to detect:

• Unusual outbound connections to unknown IPs or domains.
• High bandwidth usage from idle systems.
• Repeated connections to known mining pool addresses.
   For businesses, implementing deep packet inspection (DPI) or network behavior analysis can help detect such anomalies.

5. Check Browser Extensions and Scripts

Review and audit installed browser extensions regularly, especially those from unverified sources. You can also use browser tools or plugins to detect and block mining scripts in real time, such as No Coin or MinerBlock.

6. Inspect Cloud and Server Workloads

 If you’re using cloud infrastructure or enterprise servers, regularly audit your instances for:

• Abnormal CPU usage on virtual machines.
• Unauthorized background processes.
• Unexpected costs or billing spikes, especially for compute resources.

7. Use Threat Intelligence Feeds

Security solutions integrated with threat intelligence feeds can detect and block known cryptojacking domains, scripts, and behaviors. This helps you stay ahead of emerging cryptojacking campaigns.

How to Prevent Cryptojacking

Cryptojacking is a silent, but resource-draining threat, and stopping it requires a combination of proactive security measures. With attackers using sophisticated tactics to hijack your devices or networks for cryptocurrency mining, it’s important to adopt multiple layers of defense to protect your systems. Here’s how you can prevent cryptojacking from impacting your devices and business operations.

1. Invest in Reliable Security Software

One of the most effective ways to protect your device from cryptojacking is to have reliable antivirus or endpoint protection software in place. A good security solution will detect and block known cryptojacking malware, suspicious activity, and unusual behavior patterns. Make sure to enable real-time protection and keep your antivirus software updated regularly to stay ahead of emerging threats.

Additionally, opt for security software with advanced features such as heuristic detection, which can identify cryptojacking scripts even if they haven’t been previously recognized by the software’s virus database.

2. Block Cryptomining Scripts in Your Browser

A significant number of cryptojacking attacks are executed through web browsers, making it critical to take steps to block cryptomining scripts. While some cryptojackers inject mining code directly into websites, you can use browser extensions like No Coin, MinerBlock, or uBlock Origin to block these scripts. These tools will prevent mining scripts from executing without your knowledge while browsing.

Additionally, regularly clear your browser cache and review installed extensions. Be cautious of any unfamiliar or suspicious browser add-ons, as these can sometimes carry hidden cryptojacking scripts.

3. Keep Your Software Up to Date

Cryptojackers often exploit security vulnerabilities in outdated software. It’s essential to stay on top of software updates for your operating system, applications, and plugins. Most updates include important security patches that fix vulnerabilities that cryptojackers and other malware can target. Set up automatic updates whenever possible to ensure that your software is always current.

4. Be Cautious with Free and Pirated Software

One common method of distributing cryptojacking malware is through cracked software and pirated applications. These files are often bundled with hidden mining scripts. Avoid downloading software from untrusted sources and ensure that you’re only using reputable and verified applications. If you’re unsure about a file, always check its integrity before downloading and installing it.

By sticking to official software channels and avoiding shady download sites, you’ll reduce the risk of unknowingly installing cryptojacking malware.

5. Educate Your Team on Phishing Risks

Phishing emails remain one of the primary ways cryptojacking malware is distributed. Cybercriminals often disguise malicious links or attachments as legitimate files, and once clicked, they download malware onto the system. Conduct regular training for your team to recognize phishing attempts and suspicious emails. Teach them not to click on links from unknown sources and to verify attachments before opening them.

Additionally, using email security tools like spam filters can help block malicious emails from reaching your inbox in the first place.

6. Protect Your Cloud Infrastructure

Cryptojacking isn’t limited to individual devices; cloud servers and infrastructure are often targeted as well. Cloud computing platforms are lucrative targets because they offer massive computational power.

To safeguard your cloud infrastructure, always use strong, unique credentials for accessing servers. Enable multi-factor authentication (MFA) to add an extra layer of security and monitor your cloud resource usage closely for any unusual spikes in CPU or bandwidth.

Configure your cloud environment with restrictive access permissions to limit potential entry points for attackers, and regularly audit logs to detect any unauthorized activity.

7. Utilize a VPN for Extra Protection

Using a VPN like AstrillVPN can significantly reduce your exposure to cryptojacking attacks. A VPN encrypts your internet traffic and hides your IP address, making it harder for attackers to target your device.

Additionally, AstrillVPN offers built-in features like Ad & Tracker Blocker and Site/App Filter, which help block access to malicious websites and prevent cryptojacking scripts from executing. By routing your traffic through secure, trusted servers, a VPN can stop mining scripts from connecting to remote mining pools or command-and-control servers.

8. Monitor Network Traffic for Suspicious Activity

Cryptojacking often involves unauthorized communication with remote mining pools. By monitoring your network traffic, you can detect unusual outbound connections or data patterns that may suggest mining activity.

Tools like network intrusion detection systems (IDS) or behavior analytics solutions can help flag suspicious activity in real-time. If you notice excessive data usage, especially from unknown sources or destinations, investigate further.

9. Disable JavaScript on Untrusted Websites

JavaScript is a common method used to execute cryptojacking scripts. While it’s impractical to disable JavaScript entirely, you can disable it on untrusted or unfamiliar websites. Many browsers allow you to configure JavaScript settings, so you can selectively enable it on trusted websites and block it on others. By taking this precaution, you minimize the chances of unintentionally loading a cryptojacking script from an unsafe site.

10. Implement Network Segmentation

For organizations, network segmentation can be an effective way to limit the spread of cryptojacking infections. By dividing your network into separate zones, you can restrict access to critical systems and prevent malware from affecting your entire infrastructure. If one segment becomes infected, it’s easier to isolate and contain the threat without compromising your whole network.

Real-World Examples of Cryptojacking

Cryptojacking has been used in numerous high-profile attacks, proving its effectiveness and profitability for cybercriminals. Below are some notable cases that highlight its impact.

1. TeamViewer Exploitation (June 2024)

In mid-2024, a widespread cryptojacking campaign targeted businesses through compromised TeamViewer credentials. Attackers gained remote access to systems and deployed XMRig miners, cleverly disguising them as legitimate Windows processes. The operation went undetected for weeks in many cases, with victims only noticing performance issues or unusual fan activity.

This attack highlighted how cybercriminals are shifting from malware-based infections to credential-based intrusions, allowing them to maintain persistence without triggering traditional security alerts. The incident also underscored the importance of monitoring remote access tools and enforcing multi-factor authentication (MFA) to prevent unauthorized entry.

2. Ivanti Zero-Day Exploit (January 2024)

Early 2024 saw attackers exploiting a critical vulnerability (CVE-2024-21893) in Ivanti Connect Secure VPN to deliver cryptojacking payloads. Unlike traditional malware, this attack used fileless techniques, running miners directly in memory to evade detection.

The campaign impacted government agencies, healthcare providers, and financial institutions, with some systems mining cryptocurrency for over a month before discovery.

This case demonstrated how network appliances can serve as entry points for cryptojacking and emphasized the need for behavioral monitoring alongside conventional antivirus solutions. Additionally, it reinforced the urgency of patching known vulnerabilities in VPNs and other critical infrastructure.

3. Docker & Kubernetes Cryptojacking Wave (2023-2024)

Misconfigured Docker containers and Kubernetes clusters became prime targets for cryptojackers in 2023 and 2024. Attackers scanned for exposed APIs, deploying mining containers that auto-scaled based on available resources. One notable victim, a European tech firm, saw its AWS bill spike by $90,000 before discovering the unauthorized mining operation.

This wave of attacks revealed how cloud misconfigurations can lead to significant financial losses and operational disruptions. It also highlighted the need for strict access controls and continuous monitoring of cloud environments to detect and halt unauthorized crypto mining.

4. YouTube Malvertising Campaign (2018)

In a sophisticated malvertising attack during 2018, cybercriminals distributed cryptojacking scripts through compromised ads on YouTube and other major websites. The attack used the now-defunct Coinhive service to mine Monero through visitors’ web browsers.

Unlike typical malware infections, this required no software installation – simply loading an infected ad would initiate mining. The campaign ran undetected for months, affecting millions of users worldwide, and highlighted the risks of cryptojacking through trusted web platforms.

5. Smominru Botnet Operation (2017-2018)

The Smominru botnet, active between late 2017 and 2018, became one of the most extensive cryptojacking operations ever documented. This Windows-based malware infected over 500,000 machines globally by exploiting the EternalBlue vulnerability and conducting brute-force attacks on Remote Desktop Protocol (RDP) services.

The botnet created a massive, distributed mining network that generated approximately 8,900 Monero (worth about $3.5 million at the time). Its success demonstrated how attackers could leverage unpatched systems and weak credentials for large-scale cryptojacking campaigns.

Conclusion

Cryptojacking may not steal your data like traditional malware, but it hijacks something just as valuable, your device’s power and performance. Whether through browser scripts or stealthy malware, attackers silently exploit your resources to mine cryptocurrency, all at your expense.

The good news? Cryptojacking is preventable. By combining proactive security habits with tools like script blockers, anti-malware software, and a privacy-focused VPN like AstrillVPN, you can significantly reduce your exposure. Astrill’s features, such as StealthVPN, malicious domain blocking, and app/site filtering, add an extra layer of protection that keeps both your identity and devices safe.

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