Having been recommended the software by a friend, I went ahead and downloaded Little Snitch 2, which is an outbound firewall. This means it tells you about connections originating from your machine and allows you to block or allow them.
Wanting to see what the full version was like before I part with the cash, I found a serial number which someone had helpfully made available on Google and entered it into the program.
It immediately said the program was registered and I continued using it. However, after a few hours, it switched itself off. I enabled it again; the same thing happened.
Researching the problem, it seems that when you enter the serial number, the software phones home and checks it’s valid before enabling the full version. If it’s invalid, it says it’s valid but doesn’t fully enable (ie, it tricks you).
So we have a piece of software whose sole raison d’être is to tell you about outgoing connections, yet it doesn’t tell you when it is establishing connections itself. Not cool. I won’t be purchasing this.
To get round this naughtiness: install the software; create a rule which blocks the application ‘Little Snitch Configuration’ from connecting anywhere; then enter the serial number 32RPL63HB0-7GH4J. Tada.