Sometimes your web browser starts behaving strangely, it may be a sign your browser has been hijacked. Malicious software ( malware) can take control of your web browser and change your home page, redirect your search results to malicious sites, or you face with a barrage of popup ads.Malwares are often bundled with browser hijackers. A browser hijacker is a type of malware program that alters your computer's browser settings so that you are redirected to Web sites that you had no intention of visiting.It alter your default home pages and search pages. The hijacker can modify , control and redirect your search results and ultimately he can collect your personal information such as usernames, passwords, and credit card and banking information.
One of the easiest way is to block unwanted websites by modifying machine’s HOSTS file .What is a Host file? In a simple way Hosts file is like an address book.It is a common part of an operating system's Internet Protocol (IP) implementation, and serves the function of translating human-friendly hostnames into numeric protocol addresses, called IP addresses, that identify and locate a host in an IP network(Wikipedia).One of the feature of the HOSTS file is its ability to block other applications from connecting to the Internet, providing the entry exists.You can use HOSTS file to block ads, banners, 3rd party Cookies, 3rd party page counters, web bugs, and hijackers
You can search the Host file in WINDOWS\system32\ directory.
Open the host file in notepad and to block a website input an entry in the host file.If you want to block ad.doubleclick.net just enter 127.0.0.1 as an IP address then type ad.doubleclick.net in the host file.Each entry should be placed on an individual line. The IP address and the hostname should be separated by a space or a tab. In this way, you can block any given website by just pointing it to the IP address
When the browser hijacker or you will try to open the ad.doubleclick.net , you will see a blank page.