1. Symantec/
  2. Security Response/
  3. Attack Signatures/
  4. ECHO Chargen Loop DoS

ECHO Chargen Loop DoS

Severity: Medium

This attack could pose a moderate security threat. It does not require immediate action.


This signature detects the tandem use of the echo and chargen services.

Additional Information

The echo service repeats anything sent to it, and the chargen service generates a continuous stream of data. If used together, they create an infinite loop and result in a denial-of-service.


  • echo
  • chargen


Disable and filter chargen and echo services

Filter these servcies at the firewall or gateway devices.

To disable these services on most UNIX and UNIX-like systems:

1. Edit the inetd configuration file (e.g. /etc/inetd.conf).
2. Comment out the echo, chargen, and any other UDP services not in use.
3. Restart network services.
  • Twitter
  • Facebook
  • LinkedIn
  • Google+
  • YouTube