Cryptojacking Definition

Cryptojacking is the unauthorized use of someone’s computing resources to mine cryptocurrency. It typically occurs when malware or a malicious script is installed on a victim’s device without consent, allowing the attacker to silently use the device’s processing power to perform mining operations. The mined cryptocurrency is then sent to the attacker’s wallet.

Unlike ransomware or other disruptive attacks, cryptojacking typically operates quietly in the background, making it more difficult to detect. It affects individual users, businesses, and even servers or cloud infrastructure, consuming energy, slowing down systems, and increasing wear on hardware.

How Cryptojacking Works

Cryptojacking relies on exploiting device resources without the user’s knowledge or consent. Attackers use various methods to deploy crypto mining code and keep it running invisibly.

Malware-Based Cryptojacking

Malware-based cryptojacking occurs when malicious software is installed on a device through infected downloads, phishing emails, or software vulnerabilities. Once installed, the malware runs in the background and uses the system's CPU or GPU to mine cryptocurrency. This type of attack can persist until the malware is detected and removed. It often includes mechanisms to avoid antivirus detection and to restart the process if interrupted.

Browser-Based Cryptojacking

Browser-based cryptojacking uses JavaScript code embedded in websites or ads. When a user visits the compromised site, the script executes in their browser, using local computing power for mining as long as the page remains open. This method doesn’t require malware installation, making it easier to deploy but less persistent. It's often used by attackers targeting large websites or networks with high visitor traffic.

Cloud Resource Exploitation

In some cases, attackers gain access to cloud accounts, such as misconfigured servers or exposed credentials, and run mining software on scalable infrastructure. This allows them to use vast amounts of CPU or GPU power at the victim's expense. Cryptojacking in cloud environments can result in significant costs for utility bills and degrade service performance across the affected infrastructure.

Signs of Cryptojacking Activity

Cryptojacking is designed to operate discreetly, but certain symptoms can indicate its presence.

Performance Degradation

One of the most common signs is noticeable slowness in affected devices. Applications may take longer to load, fan speeds may increase due to overheating, and systems may become unresponsive even during basic tasks. This is caused by excessive CPU or GPU usage, which is diverted away from normal operations to support mining.

Unexplained System Resource Usage

System monitors may show high CPU usage even when no intensive applications are running. In browser-based attacks, resource spikes often align with visiting specific websites. Users or IT teams who track system performance regularly are more likely to catch these anomalies early.

Increased Electricity or Cloud Costs

Cryptojacking can drive up electricity bills and cloud resource charges. Mining operations consume power continuously, especially when running across multiple systems or virtual machines. In cloud environments, attackers may create new instances or increase compute limits to maximize returns, often going unnoticed until billing anomalies arise.

Methods Used to Spread Cryptojacking

Attackers use several techniques to deliver and execute mining scripts. These methods vary in sophistication and target reach.

Phishing and Email Attachments

Fake emails containing links or attachments are a common method of delivering cryptojacking malware. Once opened, these files install background processes that mine crypto without the user’s awareness. Well-crafted phishing campaigns often mimic legitimate sources to increase success rates.

Exploiting Software Vulnerabilities

Unpatched operating systems, outdated applications, or insecure browser plugins can be exploited to gain access to devices. Once access is obtained, attackers install mining software and attempt to maintain persistence. Regular patching and software updates can significantly reduce this risk.

Compromised Websites and Ads

Attackers sometimes inject mining scripts into legitimate websites through vulnerable ad networks or plugins. Visitors unknowingly run the script in their browser, contributing their device’s resources to the attacker’s mining operation. This method doesn’t leave malware on the user’s device, making it more transient but more challenging to trace.

Impact of Cryptojacking

Cryptojacking has economic, operational, and security consequences for both individuals and organizations.

Financial and Operational Costs

Mining operations increase power usage, degrade hardware, and may lead to higher cooling needs or device replacements. In enterprise environments, this can translate to significant infrastructure and maintenance costs. Cloud-based cryptojacking can cause budget overruns in minutes if not detected quickly.

Security Vulnerabilities

A system compromised by cryptojacking may also be vulnerable to other forms of cyberattacks. Cryptojacking malware often opens the door to further exploitation, especially if remote access or command-and-control channels are active. This weakens the overall cybersecurity posture and increases the attack surface.

Productivity Loss

For businesses, cryptojacking can significantly reduce performance across workstations, resulting in delays and increased frustration. In environments where computing resources are mission-critical, performance loss can affect service quality or delivery timelines. Downtime for remediation also diverts IT resources from other priorities.

How to Prevent Cryptojacking

Proactive strategies can reduce the risk of cryptojacking and improve overall cybersecurity resilience.

Use Endpoint Protection Tools

Antivirus software with cryptojacking detection capabilities or anti-malware tools can help block malware and suspicious scripts. Some solutions specifically monitor resource usage and detect known mining behaviors. Regular scanning and real-time monitoring provide a defense layer against common attack vectors.

Block Mining Scripts in Browsers

Browser extensions and settings can block known crypto mining domains or JavaScript code. Tools like NoScript, uBlock Origin, or browser-level crypto protections can prevent scripts from running without user consent. Web filtering systems can also block sites associated with browser-based cryptojacking.

Enforce Software Updates

Maintaining current versions of operating systems, browsers, and plugins helps close security gaps. Attackers often target known vulnerabilities that are already patched in recent updates. Automated patching policies can reduce the window of exposure.

Monitor System and Network Activity

High resource usage, unusual outbound traffic, or unauthorized cloud activity can be signs of cryptojacking. Regular audits and network monitoring tools help detect anomalies early. Security teams can set alerts to trigger investigations when thresholds are exceeded.