Adware software , the main purpose of which is to deliver advertisements to the user.
Sometimes the means used by adware lead to a different classification, such as browser hijacking, but it will still be adware.
There are many types of adware and most of them would be classified as browser hijackers.
A user may be “hit” with advertisements while browsing the internet, which may lead them to believe that they are coming from the website they are visiting, when they are not. They can come in the form of pop-ups or pop-unders, but they could, just as well, appear to be embedded in the website itself.
For example, there are adware programs that change pieces of text on the website the user is visiting, in links that show pop-ups or tooltips when the mouse cursor passes over them. Most of the above are in the form of browser extensions / add-ons.
Then, there are also adware programs that change the home page, your search engines, or even the shortcuts on the user's computer that open the browser.
Other means of directing the user to a location of the adware's choosing are proxies, hosts-file changes, and DNS-hijacks.
DNS hijacks are known to occur on poorly protected routers and can even occur on some routers, even if they are properly password protected.
Another method uses the Windows to display ads at regular intervals or on certain occasions.
LSP hijackers are placed in the TCP/IP stack, and can modify or add to the content of Internet traffic.
