Internet-Security.com UDP port 19 details

UDP port 19 is used by the Character Generator Protocol (CHARGEN, RFC 864).
Unix-like systems implemented CHARGEN via inetd/xinetd’s built-in “chargen” service (e.g., BSD variants and many older Linux distributions).
Microsoft Windows offered CHARGEN through the optional “Simple TCP/IP Services” feature in older versions (e.g., Windows XP/7 and Windows Server 2003/2008).
Cisco IOS provides CHARGEN as part of the “udp-small-servers” feature when enabled.
Exposed CHARGEN services on UDP/19 have been widely abused for reflection/amplification DDoS attacks.

UDP 19