Who is trying to log into my SSH?

Who is trying to log into my SSH?

grep -i 'from invalid user' secure | sed "s/.* invalid user \([^ ]\+ [^ ]\+\) port .*/\1/i" | cut -f1 -d' ' | sort -u

and where are they coming from?

grep -i 'from invalid user' secure | sed "s/.* invalid user \([^ ]\+ [^ ]\+\) port .*/\1/i" | cut -f2 -d' ' | sort -u