Cryptojacking is a silent but highly damaging cybersecurity threat where hackers hijack your computer's processing power to mine cryptocurrency without your consent. Unlike ransomware, which announces itself, cryptojacking is designed to stay hidden, slowing down your system, increasing electricity bills, and potentially damaging hardware through overheating. This guide will show you exactly how to identify, remove, and prevent these hidden mining scripts.

Step 1: Identify Unusual System Resource Usage

The first sign of cryptojacking is a sudden, unexplained drop in performance. Mining scripts require massive amounts of CPU or GPU power.

• For Windows users: Press Ctrl + Shift + Esc to open the Task Manager. Click on the 'Processes' tab and sort by 'CPU'. If your browser or an unknown process is using 80-100% of your CPU while you aren't doing intensive work, you may be infected.
• For Mac users: Press Command + Space, type Activity Monitor, and hit Enter. Check the '% CPU' column for any suspicious spikes.

Step 2: Check for Browser-Based Cryptojacking

Most modern cryptojacking occurs via 'drive-by mining', where a malicious script runs inside your web browser while a specific tab is open. To stop this:

• Close all tabs: If your CPU usage drops immediately after closing your browser, the script was likely running on a website you visited.
• Check Browser Task Manager: In Google Chrome, press Shift + Esc to see which specific tab or extension is consuming resources. If a 'Subframe' or 'Background Page' is using high CPU, end that process immediately.

Step 3: Audit and Remove Malicious Extensions

Malicious browser extensions are a common delivery method for mining scripts. Even legitimate extensions can be sold to developers who turn them into malware.

• Navigate to your browser's Extensions menu (chrome://extensions or similar).
• Review every extension: If you don't remember installing it, or if it serves no clear purpose, click Remove.
• Disable all extensions: If the high CPU usage stops, re-enable them one by one to find the culprit.

Step 4: Run a Specialized Malware Scan

Standard antivirus programs sometimes miss browser-based miners. You need a tool that specializes in Potentially Unwanted Programs (PUPs) and malicious scripts.

• Download and run Malwarebytes or HitmanPro. These tools are highly effective at detecting 'CoinMiner' signatures.
• Perform a Full System Scan to ensure the miner hasn't installed a persistent executable on your hard drive.
• Quarantine and delete any detected threats.

Step 5: Block Future Mining Scripts

Once your system is clean, you must implement preventative measures to ensure you aren't re-infected.

• Install an Anti-Mining Extension: Extensions like NoCoin or minerBlock are specifically designed to block mining scripts in the browser.
• Use a Robust Ad-Blocker: Tools like uBlock Origin have built-in filters to block known cryptojacking domains.
• Keep Software Updated: Hackers often use exploits in outdated browsers or operating systems to inject mining code. Enable Automatic Updates for your OS and browser.

Step 6: Check Your Network Hardware

In some advanced cases, cryptojacking malware can infect Wi-Fi routers or Network Attached Storage (NAS) devices. If your PC is clean but your network is slow, reset your router to factory settings and update its firmware to the latest version to clear any infected memory.

💡 Pro Tip: Keep your software updated to avoid these issues in the future.