shadow/man/login.defs.d/LOG_UNKFAIL_ENAB.xml

<!--
   SPDX-FileCopyrightText: 1991 - 1993, Julianne Frances Haugh
   SPDX-FileCopyrightText: 1991 - 1993, Chip Rosenthal
   SPDX-FileCopyrightText: 2007 - 2008, Nicolas François
   SPDX-License-Identifier: BSD-3-Clause
-->
<varlistentry>
  <term><option>LOG_UNKFAIL_ENAB</option> (boolean)</term>
  <listitem>
    <para>
      Enable display of unknown usernames when login failures are
      recorded.
    </para>
    <para>
      Note: logging unknown usernames may be a security issue if an user
      enter her password instead of her login name.
    </para>
  </listitem>
</varlistentry>