Disconnect the computer from the network, then run a full scan with Microsoft Defender or your business antivirus. If the scan finds something serious, or the computer handles sensitive data, have it checked professionally — some malware hides from simple scans.
Common causes
Malicious downloads
Fake software, cracked programs, and bundled installers are common sources.
Email attachments
Attachments and links in phishing emails install malware.
Browser extensions
Unwanted extensions hijack searches and show ads.
Missing updates
Outdated Windows, browsers, and plugins have known security holes.
How to fix it, step by step
- 1
Disconnect from the network
Turn off WiFi or unplug the cable to stop the malware from spreading or sending data.
- 2
Run a full antivirus scan
Use Microsoft Defender's full scan or Microsoft Defender Offline scan.
- 3
Remove unknown programs and extensions
Uninstall software and browser extensions you don't recognize.
- 4
Reset the browser
Reset browser settings to remove hijacked home pages and search engines.
- 5
Change passwords from a clean device
If you've used passwords on the infected computer, change them from another device.
When to call a technician
If the computer stores customer data or connects to shared drives, don't rely on a quick scan. We investigate, clean or rebuild the computer, check the rest of the network, and set up protection to prevent a repeat.
On-site support across Orange County · see our IT support, managed IT, Microsoft 365 support and cybersecurity services.
Frequently asked questions
Is Microsoft Defender good enough for a business?
Defender is solid for basic protection. Businesses benefit from managed security with central monitoring and alerts.
Can malware spread to other computers?
Yes, especially through shared drives and the network. That's why disconnecting is the first step.
Should I reinstall Windows?
For serious infections, a clean rebuild is often the safest option, after backing up files carefully.