Thanks again
Right, I have checked DNS and both those numbers are listed there already.
As for the rest of your message, I don't really understand its meaning I am afraid. I am the sole user of the Mac. Only me and my 6 year old daughter live in the house so it's unlikely she would would have done anything... No one else could have had access to the Mac What I find peculiar is the actual message, with the Arabic word in there and the signature Baba. I don't speak Arabic and know noone who does. The whole thing makes no sense to me whatsoever.
I access the Internet via Google Chrome which is situated on the dock as my default browser. I also tried with Safari and got the same message. The message only appears on Half of the websites I try to access. It's happening with YouTube, Soundcloud and Ultimate-Guitar. I can get Yahoo, BBC, Google and so on without problem.
The Mac is connected to my router via Wireless and the router is a BT Hub 3 (I live in the Uk).
What do you suggest I should do?