I finally set myself up a virtual server. As soon as I did that, it started getting hit by probes from across the world. To handle this, I installed fail2ban, which will ban source addresses based on log file entries, for a certain amount of time. This certainly helped, but I noticed that some of these were persistent offenders.
Fortunately, Phil Hagen’s Scratch Pad had a ready rolled solution: 21 offences and you are out permanently. I have just set this up, so will monitor over the week.