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Man page lists /etc/telnetrc and .telnetrc, neither of which is present on my machine, so I've nowhere to start.

I've also tried sudo faillog -u $USER -m 3 , but that didn't produce desired result for telnet.

System: Ubuntu 14.04 LTS

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tl;dr: man pam_faillock or man pam_tally

Login authentication uses the Pluggable Authentication Mechanism. This has a configuration file per login service located in /etc/pam.d/. These configuration files refer to "PAM modules" which implement aspects of authenticaton and authorisation. Take a moment to see a concrete example by looking at /etc/pam.d/login, which is the authentication mechanism for the "login" command.

The module "pam_faillock" allows the counting and testing of the number of login attempts. Optionally, locked accounts can be automatically unlocked after some interval.

The manual page for pam_faillock has example /etc/pam.d configurations.

Most Linux distributions have each service refer to a single all-services authentication configuration (/etc/pam.d/password-auth in Red Hat land, /etc/pam.d/common-password in Debian-land). So use the example in the man page to inform your changes to those common files. To ease testing you may prefer to get the configuration right for just one service -- allowing you to login through other services to fix any errors -- before attempting to modify the all-services configuration.

Slightly older Linux distributions provide a similar facility using pam_tally.

  • pam settings dont seem to be working for a strange reason. Only /etc/login.defs. I've changed the default 5 login attemnts to 3 and it works with giving incorrect password on telnet localhost. Is that how it should work or is it some anomaly? – Sergiy Kolodyazhnyy Feb 9 '15 at 22:24

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