I would just like to point out that there have been several SSH attacks against my computer today that seem to be specifically targeting Bitcoin users. I believe the target IPs to be scraped from the Bitcoin network itself. I received about 100 login attempts to accounts called "bitcoin", "bitcoin1", "bitcoin2" and "namecoin" from an IP in China (220.165.5.4). If anyone knows what particular Bitcoin client or setup these attacks are targeting it would be useful to know, otherwise I would just like to remind everyone to keep their SSH secure, ideally with the AllowUsers directive to allow only specific accounts SSH access.
You might catch even more stuff you don't want if you firewall your machine in general. Many people get by fine blocking anything Chinese from coming in. I firewall out about 70% of the IPV4 address space and don't miss anything by doing so. If you have linux or BSD, you can use TCP wrappers and a program like denyhosts to dynamically detect and lock out SSH probers, which are very common due to a few common security tools that seem to turn up in use a lot.
http://en.wikipedia.org/wiki/TCP_Wrapper