Just about every shared host is under attack at all times. Servers where thousands of people run old versions of widely used open source software (blogs, CMS's, contact forms, etc) are such easy targets for exploiting known security flaws.<p>Aside from not using shared hosting at all, at least don't use shared hosting provided by a domain registrar. The combination of supporting millions of customers and hosting not being their primary business means hosting MUST be treated as a commodity for them to offer it at all. They're not going to have the people bandwidth to help customers clean up their sites after they're hijacked.