As some of you might have noticed, we had some downtime yesterday. This is due to some gentlemanly folk who decided to use the server to send out spam. I thought I had configured the mail server well, but apparently some things can go wrong. For example, the fact that the root account doesn’t have a password set doesn’t mean that people can’t log in. Apparently my SASL service thought that by “no password” I meant “log people in with whatever”, and allowed people to log in anyway.
If you are running postfix with SASL, be aware that “no password” (or blank password) means that people can still log in by using the username, so if root has a blank password nobody will be able to log in through ssh, the console, or most other ways, but with SASL they can just use root/root and they’re golden.
I’m pretty sure this is a security hole, but I’ve just locked the account now and hopefully everything is fine. I hope you haven’t been greatly inconvenienced.