We are seeing a persistent number of web attacks on our site by hackers which seem specificaly designed to attack a WordPress site.
These attacks take the form of Remote File Intrusion attempts. These are where hackers try to force a vulnerable extension into loading PHP code directly from their server. This is done by passing an http(s):// or ftp:// URL in their request, pointing to their malicious site.
They are using Wordpress plugins in the main, so if you are a WordPres site this is something be to aware of. The source of the attacks is a little varied but the IP addresses tend to indicate the US and Canada, but of course these may be compromised addresses hiding the real source.