TL;DR: Warning signs include an extension you don't remember installing, your browser's homepage or search engine changing without your permission, or a spike in ads and pop-ups after installing something new. Review your installed extensions in your browser's extension manager and remove anything you don't recognize or no longer use, only install extensions from official web stores with a solid install count and reviews, and reset your browser's homepage/search engine settings if they were changed.
Warning signs include an extension you don't remember installing, your browser's homepage or search engine changing without your permission, or a spike in ads and pop-ups after installing something new.
What Usually Causes This
Fake extensions are often bundled with free software downloads, disguised as a legitimate tool (like a PDF converter or coupon finder), or occasionally pushed through a compromised update to a previously legitimate extension.
What to Do About It
Review your installed extensions in your browser's extension manager and remove anything you don't recognize or no longer use, only install extensions from official web stores with a solid install count and reviews, and reset your browser's homepage/search engine settings if they were changed.
If this looks similar to something else you've seen, it's worth reading How to Spot a Fake Public WiFi Hotspot.
This pattern shows up elsewhere too — see How to Spot a Fake VPN App.
Frequently Asked Questions
What are the real warning signs?
Warning signs include an extension you don't remember installing, your browser's homepage or search engine changing without your permission, or a spike in ads and pop-ups after installing something new.
What usually causes this?
Fake extensions are often bundled with free software downloads, disguised as a legitimate tool (like a PDF converter or coupon finder), or occasionally pushed through a compromised update to a previously legitimate extension.
What should I do about it?
Review your installed extensions in your browser's extension manager and remove anything you don't recognize or no longer use, only install extensions from official web stores with a solid install count and reviews, and reset your browser's homepage/search engine settings if they were changed.
Should I be worried if I only see one sign?
One sign alone (like a slower device) is usually not cause for alarm — most single symptoms have mundane explanations. Multiple signs together, especially unexpected data usage or unfamiliar apps, are worth investigating.