If your website, in common with roughly 25% of all websites, is running WordPress then it’s pretty much certain that it’s being constantly attacked. WordPress is to hackers what raw meat is to jackals because unless sites are assiduously maintained, they quickly become vulnerable to a huge number of exploits.
The root cause of this vulnerability is WordPress’ ecosystem of complex core software augmented by thousands of third party developers whose themes and plugins are often buggy and not quickly (or often, never) updated to fend off known security problems. Add to that many site owners being slow to update their core WordPress installation and you have an enormous and easily discovered collection of irresistible hacking targets.
Source: NW Security 1