I've had some failed SSH login attempts listed in it's log, from someone unknowned. Appears to have been a dictionary attack. The first name used was the typical "Admin", but what got my attention was that the second username he/she used was my own user. Where could this intruder possibly get this info? it's an uncommon and complicated name. My system is quite secured (a router and a personal firewall, and running few server apps, and no web server). And I'm the only one with physical access, and of course i have not told anyone about my username.

I just can guess

1.) finger (if you firewall is not configured correctly)
2.) sshd ist answering on each request. maybe the relpy of the server has been configured somehow ?
3.) if this does not help give nessus a trie!