Replacing Sensitive Data in the Audit Log

When audit logging is enabled and includes DML category events, sensitive data, such as password columns, are exposed in the message portion of the audit log. You can configure the audit log appender (SLF4JAuditWriterAppender) to replace strings in log message to mask the sensitive data. The replace function uses a regular expressions to modify the data. For more information on using the replace filter, see the logback documentation.

Additionally, because the auditing is configured through a text file in the file system, the file is vulnerable to OS-level security breaches. You can secure the file by setting the permissions to 0600 on the audit files. Be aware that if other tools look at the data, changing this setting can cause read problems. Alternately, you can store the audit file on an OS-level encrypted file system such as Vormetric.

Before sharing log files, redact sensitive data.


  1. Locate the logback.xml file. The location of the logback.xml file depends on the type of installation:

    • Package installations: /etc/dse/cassandra/logback.xml

    • Tarball installations: <installation_location>/resources/cassandra/conf/logback.xml

  2. Open the logback.xml file in a text editor.

  3. Locate the pattern element.

    <!--audit log-->
    <appender name="SLF4JAuditWriterAppender" class="ch.qos.logback.core.rolling.RollingFileAppender">
        <file>${cassandra.logdir}/audit/audit.log</file> <!-- logfile location -->
          <pattern>%-5level [%thread] %date{ISO8601} %F:%L - %msg%n</pattern> (1)
          <!-- the layout pattern used to format log entries -->
        <rollingPolicy class="ch.qos.logback.core.rolling.FixedWindowRollingPolicy">
          <maxIndex>20</maxIndex> <!-- max number of archived logs that are kept -->
        <triggeringPolicy class="ch.qos.logback.core.rolling.SizeBasedTriggeringPolicy">
          <maxFileSize>200MB</maxFileSize> <!-- The size of the logfile that triggers a switch to a new logfile, and the current one archived -->
    <logger name="SLF4JAuditWriter" level="INFO" additivity="false">
        <appender-ref ref="SLF4JAuditWriterAppender"/>
    1 Pattern element
  4. Using the replace function on the message text to replace the first term with the second term. Here is an example to find password set to any characters and replace the password characters with xxxxx:

    %replace(%msg){"password\s*=\s*'.*'", "password='xxxxx'"}

    DataStax automatically masks the password specified in the CREATE ROLE command.

  5. Restart the node or wait for the configuration to automatically reload.

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