Cryptojacking: What It Is and How It Works

A silent thief could be running up your electricity bill and slowing your devices to a crawl, all without you noticing. This intruder is a form of malware called cryptojacking, a malicious practice that secretly hijacks your computer’s processing power to mine cryptocurrency for an attacker.

While it might seem like a minor annoyance causing your fan to whir and your battery to drain, the implications are far more serious. Cryptojacking degrades system performance, inflates energy and cloud computing costs, and often serves as a smokescreen for more significant security breaches.

Protecting your digital assets requires recognizing the signs of this stealthy threat and knowing how to fight back.

How Cryptojacking Works

To succeed, a cryptojacking attack must gain access to a device’s processing power and remain hidden. Attackers achieve this through two primary methods: by injecting scripts into web browsers or by installing malicious software directly onto a computer.

Each technique is designed for stealth, allowing the unauthorized mining to persist for long periods while avoiding detection.

Unauthorized Versus Legitimate Mining

Cryptocurrency mining is a legitimate activity when individuals use their own hardware and electricity to generate new coins or validate transactions. Participants knowingly dedicate their computing power in exchange for potential rewards.

Cryptojacking, however, is the unauthorized and malicious form of this practice. It operates without the user’s knowledge or consent, effectively stealing resources.

Attackers prioritize stealth over speed, quietly harvesting processing power in the background to avoid alerting the victim, which allows the malicious activity to persist for a longer duration.

Common Modes of Operation

Attackers typically employ one of two methods to execute a cryptojacking attack. The first is in-browser mining, which involves injecting a malicious script into a website or an online advertisement.

When a user visits the compromised webpage, the script automatically runs inside their browser, forcing the device to begin mining. In most cases, the mining stops once the user closes the tab, but some sophisticated scripts can hide in persistent pop-under windows.

The second method is host-based, where an attacker tricks a user into downloading and executing malware. This malware installs a cryptomining program that runs continuously as a background process, making it more persistent and difficult to remove than a browser-based script.

Attacker Payloads and Objectives

The primary objective of a cryptojacking attack is financial gain. To achieve this, attackers deploy payloads containing specialized mining software.

One of the most common tools is XMRig, a high-performance miner often used to mine Monero (XMR). Monero is a popular choice for illicit activities because its privacy-focused design makes transactions anonymous and difficult to trace.

Attackers carefully configure these payloads to ensure persistence and evade detection. They may schedule the miner to run at specific times, disguise it as a legitimate system process, or throttle its resource consumption to prevent a noticeable drop in system performance that might otherwise alert the user.

Entry Vectors and Execution Paths

Attackers use a variety of techniques to deliver and execute cryptojacking malware, adapting their methods to target everything from individual user browsers to large-scale enterprise cloud environments. These entry points often exploit common security weaknesses, such as unpatched software, system misconfigurations, or a lack of user awareness.

Once inside a system, attackers employ specific strategies to ensure their miners run for as long as possible without being discovered.

Browser-Based and Drive-By Mining

One of the most common entry vectors is “drive-by” mining, which requires no user interaction beyond visiting a compromised website. Attackers inject malicious JavaScript or WebAssembly (Wasm) code into a legitimate but vulnerable site, or they purchase ad space to distribute infected advertisements.

When a user’s browser loads the page or ad, the embedded script begins executing, hijacking the CPU to mine cryptocurrency. In some cases, the mining script runs from a compromised browser extension that the user willingly installed.

While many of these attacks end when the user closes the browser tab, more advanced versions use hidden pop-under windows or other browser tricks to persist long after the user has navigated away.

Server, Cloud, and Container Exploits

Attackers frequently target servers and cloud infrastructure due to their powerful processors and “always-on” availability. They scan for publicly exposed and misconfigured services, such as unprotected Docker API endpoints, Kubernetes dashboards, or outdated Jenkins servers with known vulnerabilities.

After gaining an initial foothold, the attacker deploys a cryptominer as a binary, a script, or a container. In cloud environments, a compromised account can be particularly devastating.

Attackers often abuse autoscaling capabilities to programmatically deploy a large number of virtual machines for mining, leading to an astronomical and unexpected increase in cloud computing bills.

Techniques for Persistence and Evasion

To maximize their profits, attackers build persistence and evasion mechanisms into their malware. To ensure the miner survives a system reboot, it is often installed as a background service or configured as a scheduled task that runs at regular intervals.

Evasion tactics are equally important. Many miners are designed to throttle their CPU consumption, using just enough resources to be profitable without causing a dramatic performance drop that might alert a user or system administrator.

Attackers may also attempt to tamper with or disable security monitoring agents. Furthermore, communications with the remote mining pool are frequently encrypted, hiding the malicious traffic from network inspection tools.

Signs, Impacts, and Risks

Beyond its stealthy nature, cryptojacking leaves a trail of tangible consequences that affect both individual users and entire organizations. The impacts are not just technical; they translate into real-world costs and significant security vulnerabilities that demand attention.

Symptoms on Endpoint Devices

One of the most immediate signs of a cryptojacking infection is a noticeable decline in device performance. Since the malware is designed to consume CPU or GPU cycles, users may experience a sluggish system, slow application response times, and general unresponsiveness.

Physical indicators are also common, such as devices overheating or computer fans running at maximum speed even when the system is idle. On laptops and mobile devices, a sudden and dramatic drop in battery life is another telltale sign that a resource-intensive process is running without permission in the background.

Business and Operational Costs

For businesses, cryptojacking introduces hidden operational costs that can quickly escalate. On-premise servers infected with mining malware will consume significantly more electricity, leading to unexpectedly high utility bills.

In cloud environments, the financial impact can be even more severe. Attackers who compromise cloud accounts often deploy miners that abuse autoscaling features, causing illicit resource consumption that results in massive, unforeseen bills.

This unauthorized activity also degrades service performance, putting organizations at risk of violating Service Level Agreements (SLAs) with their customers and damaging their reputation.

Broader Security Implications

Perhaps the most serious risk of cryptojacking is what it can hide. The presence of a mining script is a clear signal that a system has been compromised, and the initial intrusion could serve as a foothold for more dangerous attacks.

An attacker who has gained enough access to install a cryptominer can just as easily deploy ransomware, steal sensitive data, or move laterally across the network. The resource hijacking itself can mask this other malicious activity, expanding the potential blast radius far beyond simple compute theft and turning a performance issue into a major security incident.

Detection and Indicators

Effective detection of cryptojacking requires a multi-layered approach that looks for specific signals across hosts, networks, and cloud infrastructure. While performance degradation is a common symptom, security teams must rely on more technical indicators to confirm the presence of mining malware.

Monitoring Host and Process Signals

On an infected endpoint or server, cryptojacking malware often reveals itself through its behavior. System administrators can look for unfamiliar processes consuming a disproportionate amount of CPU resources, sometimes disguised with generic names to evade simple detection.

Investigating the system’s scheduled tasks on Windows or cron jobs on Linux can reveal persistence mechanisms designed to relaunch the miner if it is terminated or the system is rebooted. Examining the file system for recently created binaries associated with known mining tools, such as XMRig, provides another strong indicator of a compromise.

Analyzing Network and Cloud Telemetry

Network monitoring offers another critical vantage point for detection. Cryptomining software must communicate with a remote mining pool to receive work and submit results.

This creates consistent outbound network traffic that can be identified by security tools. Analysts can look for connections to known malicious domains or IP addresses associated with mining pools.

In cloud environments, telemetry provides clear signs of illicit activity. Sudden and unexplained spikes in computing costs, anomalous data egress, or the unexpected activation of autoscaling rules that provision new virtual machines are all red flags.

Unusually high or persistent GPU utilization on instances not designated for such workloads is another powerful signal of a cryptojacking intrusion.

Employing Analytic Detection Methods

A proactive strategy involves implementing advanced analytic methods to distinguish malicious activity from normal operations. This begins with establishing a clear baseline of typical resource usage, network behavior, and application performance for all systems.

Endpoint Detection and Response (EDR) solutions and network security monitors can then use this baseline to automatically flag significant deviations that may indicate cryptojacking. In the cloud, monitoring tools can correlate unusual API calls with unexpected resource provisioning.

By combining and correlating alerts from endpoint, network, and cloud monitoring systems, organizations can build a comprehensive view of a potential attack, confirm the threat with high confidence, and accelerate their incident response.

Prevention and Response

A robust defense against cryptojacking combines proactive security measures to prevent infections with a clear, systematic plan for responding when a compromise occurs. Protecting assets requires hardening systems at every level, from individual browsers to complex cloud infrastructures.

When prevention fails, a swift and thorough incident response is essential to contain the damage and restore system integrity.

Hardening Browsers and Endpoints

Protecting user devices is the first line of defense. Installing reputable ad-blocking and script-blocking browser extensions can stop many browser-based mining scripts before they can execute.

Users should be cautious when installing any browser extension, vetting its permissions and publisher to avoid adding a malicious tool to their system. Regular and timely patching of operating systems, web browsers, and other software is critical for closing the vulnerabilities that attackers often exploit to install malware.

Additionally, organizations can implement application control or whitelisting policies that restrict the execution of unauthorized software, effectively stopping mining binaries from running.

Implementing Cloud and Container Safeguards

In server and cloud environments, security must be built into the architecture. Adhering to the principle of least-privilege for Identity and Access Management (IAM) is fundamental; user and service accounts should only have the minimum permissions necessary to perform their roles.

Properly configuring network firewalls with egress filtering rules can block outbound connections to the IP addresses of known mining pools. For organizations using containers, security best practices include scanning container images for vulnerabilities before deployment and using digital signatures to verify their integrity.

Applying runtime security policies in Kubernetes or other container orchestrators can prevent unauthorized processes from executing inside a running container, stopping a miner in its tracks.

Executing Incident Response Actions

When detection systems flag a cryptojacking incident, a structured response is required to eradicate the threat. The first step is to immediately isolate the affected system from the network to prevent the attacker from moving laterally or exfiltrating data.

Next, security teams must identify and terminate the malicious miner process. It is crucial to then find and remove any persistence mechanisms, such as scheduled tasks or startup services, that the attacker may have put in place.

Following containment, all credentials, API keys, and secrets on the compromised system must be rotated. The original entry point must be identified and patched to prevent reinfection.

Finally, the domains and IP addresses associated with the attacker’s mining pool should be blocked at the network perimeter.

Conclusion

Cryptojacking represents a unique and persistent threat, turning an organization’s own assets against it for an attacker’s financial gain. It operates in the shadows, degrading performance, inflating operational costs, and creating an entry point for more destructive attacks.

Effectively countering this menace requires a comprehensive strategy that integrates proactive defenses with vigilant monitoring and a well-defined response plan. Secure configurations and endpoint hardening form the foundation of prevention, while behavioral detection across networks and cloud environments provides the necessary visibility to catch intruders.

When an infection is found, a disciplined and rapid response is essential not only to remove the miner but also to secure the environment against further intrusion. By adopting a layered security posture, organizations can minimize the performance impact and financial costs of cryptojacking while significantly reducing the risk of a minor resource theft escalating into a major security incident.