Cryptojacking is the unauthorized use of someone else's computing device to mine cryptocurrency. Attackers embed mining code in websites, browser extensions, or malware that silently uses your CPU and GPU resources to generate cryptocurrency for the attacker — consuming your electricity and degrading device performance.
Unlike ransomware, cryptojacking does not lock your files. It operates silently in the background, making it one of the harder-to-detect forms of malware.
How Cryptojacking Works
Browser-based cryptojacking: JavaScript mining code runs in your browser when you visit a compromised website. The code mines cryptocurrency for as long as you have the tab open. Closing the tab stops the mining.
Malware-based cryptojacking: Software installed on your device runs mining code continuously, even when you are not browsing. This type persists across reboots and is harder to detect.
Supply chain attacks: Legitimate software updates or plugins are compromised to include mining code. This allows cryptojacking to spread through trusted distribution channels.
Signs of Cryptojacking
Significantly increased CPU usage (visible in Task Manager or Activity Monitor) Device running hotter than usual Fan running louder and more frequently Device performance noticeably slower Increased electricity consumption (for desktop/mining-grade attacks) Battery draining faster on laptops and phones
Detection
Open Task Manager (Windows) or Activity Monitor (macOS) while browsing. If a browser tab or background process is consuming unusually high CPU — 50-100% — without obvious explanation, cryptojacking may be occurring.
Browser extensions like minerBlock and NoCoin detect and block known cryptomining scripts.
Prevention
Keep software updated: Cryptojacking malware often exploits known vulnerabilities. Current software patches close these entry points.
Use an ad blocker with cryptomining filters: uBlock Origin blocks many known cryptomining domains and scripts by default.
Install an anti-cryptomining extension: minerBlock and NoCoin specifically target browser-based mining scripts.
Use antivirus with cryptomining detection: Modern antivirus solutions detect and block many cryptojacking malware variants.
Limit JavaScript execution: Browser security settings or NoScript extension can limit which sites can run JavaScript. This is more disruptive to normal browsing but blocks browser-based cryptojacking comprehensively.
Audit browser extensions: Remove extensions you do not recognize or no longer use — these are a common cryptojacking vector.
Cryptojacking and Email
Cryptojacking is typically delivered through malicious websites, compromised extensions, or malware. Email delivers malware through phishing attachments and links. Using Temp90 for registrations reduces the phishing surface — fewer registrations with your real email means fewer opportunities for targeted phishing that delivers cryptojacking malware.
Frequently Asked Questions
Is visiting a cryptojacking site illegal for the visitor?
No. Visitors are victims, not participants. The attacker who embedded the mining code is acting illegally in most jurisdictions.
Do mobile phones get cryptojacked?
Yes. Mobile cryptojacking exists, though it is less profitable for attackers due to lower processing power. Mobile cryptojacking causes battery drain and device overheating. The same prevention principles apply.
Is all cryptocurrency mining on websites malicious?
Some websites experimented with transparent opt-in mining as an alternative to advertising. However, this approach has largely failed commercially and most browser-based mining today is malicious. Assume browser-based mining is unauthorized unless explicitly opted in.
Conclusion
Cryptojacking is a silent resource theft that impacts device performance and electricity costs without delivering obvious visible harm. Detection through CPU monitoring and prevention through updated software, ad blockers, and anti-mining extensions are the practical defenses. Combined with the phishing awareness that prevents malware delivery through email, these measures address the primary cryptojacking attack vectors.