List failed login attempts on Yosemite I want to see if somebody has tried to log in on my computer, which is running Yosemite. I am primarily interested in tracking ssh log in attempts, as well as tracking people physically typing passwords on my keyboard to try to log in.

Closely related

List failed login attempts on Mavericks
sshd logging is determined in /etc/asl/com.openssh.sshd.

In short, you need to touch a file and then send syslogd a HUP signal:
touch /var/run/com.openssh.sshd-asl-enabled
kill -HUP $(ps -ef | grep [s]yslogd | awk '{print $2}')

After that, you will find the logs in /var/log/sshd.log