Recently one of my accounts was hijacked. I was hacked. For the first time in my life. The first thing I did was changing all passwords and keys. But still I felt not save enough. For external accounts I can not do much but for my remotely acceptable computer I could (e.g. Allow Only public-key auth). One thing I came up with is Android Notifications (or email, sms, etc.) when a ssh session is created. All I needed to do is following this answer on askubuntu.com.