Browser hijackers change the default homepage and search engine in your Internet browser without your permission.
You may find that you cannot change your browser’s homepage once it has been hijacked. Some hijackers edit the Windows registry so that the hijacked settings are restored every time you restart your computer. Others remove options from the browser’s tools menu, so that you can’t reset the start page.
Browser hijacking is used to boost advertising revenue, as in the use of blackhat Search Engine Optimization (SEO), to inflate a site’s page ranking in search results.
Browser hijackers can be very tenacious, as well as sneaky. Attackers use clickjacking, also known as a UI redress attack, by inserting multiple transparent, or opaque, layers on a webpage.
This technique can trick a user into clicking on a button or link on a page other than the one they were intending to click on. Effectively the attacker is hijacking clicks meant for one page and routing them to other another page, most likely owned by another application, domain, or both.