Sundays are a day of rest in the Thomson household: wake up, pop down to the grocers for fruit and a Sunday paper, then back for breakfast in bed.

And, this weekend, the joy of watching the wheels literally coming off Michael Schumacher in the Grand Prix.

However, such uncharitable behaviour was soon repaid. Still chortling as the race finished I went to answer a knock on the door and was met by a well dressed couple keen to discuss what religion could do for me.

Usually these visits - common as they are - invite nothing more than a polite but rapid door closure. But, flushed with hubris, I decided to argue for my atheism.

Usually it's great fun; I find debates about whether scientists really did bury fossils to keep themselves in business rather bracing.

But yesterday the gods were smiling on my visitors and, after 20 minutes of argument, I was forced to admit that maybe I could be wrong on a few issues.

They still got the door shut in their faces, but it was a much-deflated afternoon.

Heading back into the kitchen the computer bleeped at me as another port scan came up against the firewall and bounced away like a robin off a greenhouse.

These scans, often called 'attacks' by those in the security industry who want life to seem scarier than it is, are just automated checks to see whether the computer is vulnerable.

Port scanning works because you can scan a huge number of computers and collect reams of information on the vulnerable ones with no effort at all.

They are the first stage of most hack attacks and the easiest to dislodge. But occasionally even the best-protected server may be left a little misconfigured and the scans will find it.

My two visitors were the port scanners for their faith. Tirelessly they knock on door after door, usually receiving either silence or abuse.

But the reason they keep doing it is because it works: eventually someone lets them in and the next stage begins.

I decided to settle in and renew my personal firewall with a good read of The Selfish Gene.

Maybe it's time you did something similar with your IT hardware because, no matter how confident you are in its set-up, persistence always wins out.