There are a lot of toolbars and search engines out there which integrates to our browser with out permission.
Basically these toolbars always comes along with software downloaded from any unverified site , sometimes these toolbars are installed on closing any popup or advertisement.
These toolbars are technically not a virus, but they do exhibit plenty of
malicious traits, such as rootkit capabilities to hook deep into the
operating system, browser hijacking, and in general just interfering
with the user experience. The industry generally refers to it as a
“PUP,” or potentially unwanted program.
These toolbars once installed on your computer, they will hijack your browser homepage
and replace your default search engine.Futhermore, these programs will
display ads and sponsored links in your search results, and may colect
search terms from your search queries.