The network scanners discussed in this chapter all function by sending packets with very special parameters to the computer being scanned. Most Unix-like operating systems (such as Linux or Mac OS X) require superuser privileges in order to send these packets. Unicornscan and Nmap's connect scan (see Different Scan Types) mode work with normal user privileges, but advanced Nmap scans and Scanrand both require superuser privileges. Nmap works fine on Windows with an unprivileged user account.
Instead of logging in as root to gain superuser privileges, you can use sudo (see Limiting Access) to temporarily elevate your privileges.