There are a lot of ways to help protect your site against attacks, a few things to keep in mind:
Change any passwords for your account. This is always the recommended first step. In case your passwords were compromised, change your cPanel password, any FTP account passwords, and if you use WordPress or a CMS change that password as well.
Update your WordPress. When you log into your Dashboard, there should be an option to upgrade your WordPress automatically if it is not the most up to date version.
Check your .htaccess file for hacks. The .htaccess file is a popular one for hackers to attack, so make sure it is clean.
The links posted by keesiemeijer are spot on, those are just the most common fixes in my experience and a good place to start. Don't forget to keep updates of your clean, unhacked site so it can be quickly restored if your site is ever hacked again. Your host should be able to provide you with more information then just re-installing it each time, I would check with them to see if they have more information on the exact cause.