Em suma, apenas mate o PID da sessão SSH correspondente:
Encontre usuários conectados e TTYs:
w
05:04:54 up 14 days, 10:32, 2 users, load average: 0.00, 0.01, 0.05
USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT
myuser pts/0 xxx.xxx.xxx.xxx 04:48 0.00s 0.03s 0.01s sshd: myuser
myuser pts/1 xxx.xxx.xxx.xxx 05:04 2.00s 0.00s 0.00s -bash
PID correspondente (neste caso, pts / 1 correspondentes):
ps -ef | grep ssh.*pts/1
myuser 11575 11573 0 05:04 ? 00:00:00 sshd: myuser@pts/1
root 11670 11100 0 05:06 pts/0 00:00:00 grep ssh.*pts/1
Finalizar processo (neste caso, 11575, acima):
sudo kill 11575