I was surprised to say the least. At first I thought it was an internet error but I then went to my site and guess what! exactly the same thing appeared. I checked the facebook page in question and looked into making a complaint but it looks like Facebook only want to hear about complaints regarding stuff that appears on their site. I couldn't believe this miscreant would have the audacity to advertise themselves like this, they seemed pretty confident that they were untouchable! Since there didn't seem to be an option to complain, I thought I had better stop wasting my time and try to deal with the matter in hand.
I needed to know what to do next so I looked up some advice online and contacted my website host. It turns out that this is a common occurence with WordPress sites, due to their opensource nature and extreme popularity (apparently 17% of all websites are built on the platform). 5quidhost kindly secured access to my site and installed the last backup they had. I was worried that since it was two weeks old, that I would have lost some blog posts but as it turns out happily, that I had been a bit lax recently and everything was intact.
Not wanting this to happen again anytime soon, I did a bit of reading on how to keep it secure against future attack. My site had been compromised by an old plugin but I found a fantastic free security plugin called Wordfence which alerts me by email each time my site files change. I then found and blocked the IP address of the interloper (I found it on the stats page in CPanel) I also blocked a range of known dodgy IP addresses from Indonesia. I know its probably ever going to be 100% secure but now that I am aware of it I will be keeping a close eye on it from now on.
I think the biggest lesson I have learned from this is to make regular and complete backups of my site, especially after any updates. This means making a copy of the SQL database as well as the site files. Its a bit of a faff but at least I know that whatever happens I will always be able to get it back up and running.
Here are a few of the web pages I referred to after the catastrophe which are definitely worth a read if you use WordPress for your website: