From syslog.log, list each invalid username that failed login with its count, descending.
For lines like `Failed password for invalid user root from 10.0.0.7`, the username is field 9.
`grep "Failed password" /var/log/syslog.log | awk '{print $9}' | sort | uniq -c | sort -rn`
Expected: `root` 2, `admin` 1.Sign in to save your code and track progress across devices.
