This happens when a hacker installs unwanted software that modifies a web browser’s setting without your permission. These attacks are meant to either direct you to a malicious web page or lure you into letting someone remote into your computer (fake support request).
Signs of browser hi-jacking:
Unwanted ads displayed as a popup window.
Homepage changed to a different web page.
Additional toolbars added to the the browser.
Extremely slow loading pages.
Default search engine changed.
Preventing browser hi-jacking.
Don’t click on suspicious links in emails or browser windows.
Don’t install software you don’t trust, and even if you trust the software, watch for additional adware being installed (see image below).
Ensure you have current anti-virus/anti-malware installed.
If you suspect that your browser has been hi-jacked.