It may be enabled by adding the following lines to the file /etc/inetd.conf and telling inetd to reload its configuration: The CHARGEN service may be used as a source of a byte-stream for debugging TCP network code for proper bounds checking and buffer management.
Although the specific format of the output is not prescribed by RFC 864, the recommended pattern (and a de facto standard) is shifted lines of 72 ASCII characters repeating.
The following is a Linux bash script that will simulate the visual appearance of the CHARGEN service in the terminal window.
The script can be stopped by pressing Ctrl + C.The service was used maliciously to crash Microsoft domain name servers (DNS) running Windows NT 4.0 by piping the arbitrary characters straight into the DNS server listening port (telnet ntbox 19 | telnet ntbox 53).
By using a fake source address the attacker can send bounce traffic off a UDP CHARGEN application to the victim.
So notorious is the availability of CHARGEN in printers that some distributed denial of service trojans now use UDP port 19 for their attack traffic.