It appears that my site has been hacked, with many pages of spammy content added in a way that they were visible to search engines but not to general visitors to my site.
I have identified where the spam content was located on my server and deleted the entire folder, however, having asked my hosting company to check my account to see if anything looks amiss to them they have identified two suspicious files.
The first, dw_glidescroll.php, sits in the wp-admin folder for my site.
The second, bigballs.php, is in my public_html folder.
I have tried searching for these (with some comical results for the second query) but cannot identify if these are malicious files that need to be deleted.
Thanks for any help!