Symptoms
- Computer much slower than usual
- Unfamiliar programs or browser toolbars appear
- Frequent pop-up ads even outside the browser
- Antivirus or firewall gets disabled on its own
- Fans run loud even when idle
Likely causes
- CommonAdware or bundled softwareFree downloads sometimes install extra advertising software alongside the program you wanted.
- CommonTrojan or spyware infectionMalicious software from a bad download or attachment runs in the background and steals resources or data.
- PossibleBrowser hijackerAn extension changes your homepage or search engine and redirects your traffic.
- PossibleCryptomining malwareHidden software uses your CPU or GPU to mine cryptocurrency, causing constant high usage.
- Less commonRootkit or ransomware precursorMore serious infections hide deep in the system and are harder to detect with a normal scan.
What to do
- Disconnect from Wi-Fi or unplug the ethernet cable to stop data from being sent out while you investigate.
- Open Task Manager (Windows) or Activity Monitor (Mac) and look for unfamiliar processes using high CPU or memory.
- Run a full scan with your built-in antivirus (Windows Security or macOS's built-in protections) or a reputable third-party scanner.
- Remove or quarantine anything the scan flags, then restart the computer.
- Check installed programs and browser extensions for anything you don't recognize and uninstall it.
- Change your important passwords from a different, trusted device once the infection is cleared.
- Turn on automatic updates and keep real-time antivirus protection running going forward.
Tools and parts
- Reputable antivirus software
When to call a pro
If scans keep finding the same infection after removal, or you suspect a rootkit, have a computer repair shop or IT professional do a deeper cleanup or reinstall.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.