It will help them to improve their Traffic Ranking (e.g Alexa Ranking).
People are saying that some Hosting companies will do this intentionally as an Advertisement program.
If your website is getting attacked by this virus, you can follow below steps to get out of this issue.
- Rename all the .html and .php files having name as index, home, default and main. For example rename the index.php into firstpage.php
- create a new file with the original file name (e.g index.php, index.html, default.php,...)
- Place the below redirection code in new file
- Do the above steps for all the sub-folders.
By doing these steps, website can be displayed without any issue even when it is affected with virus.
If it doesn't help you can make the index files readonly so that they can not be changed by the virus.
If anybody knows the ways for removing this virus and for preventing this virus, you can share it thro' the comment section.