Auditd Module

The auditd module receives audit events from the Linux Audit Framework that is a part of the Linux kernel.

This module is available only for Linux.

This module establishes a subscription to the kernel to receive the events as they occur. So unlike most other modules, the period configuration option is unused because it is not implemented using polling.

The Linux Audit Framework can send multiple messages for a single auditable event. For example, a rename syscall causes the kernel to send eight separate messages. Each message describes a different aspect of the activity that is occurring (the syscall itself, file paths, current working directory, process title). This module will combine all of the data from each of the messages into a single event.

Messages for one event can be interleaved with messages from another event. This module will buffer the messages in order to combine related messages into a single event even if they arrive interleaved or out of order.

When running Auditbeat with the auditd module enabled, you might find that other monitoring tools interfere with Auditbeat.

For example, you might encounter errors if another process, such as auditd, is registered to receive data from the Linux Audit Framework. You can use these commands to see if the auditd service is running and stop it:

To save CPU usage and disk space, you can use this command to stop journald from listening to audit messages:

systemctl mask systemd-journald-audit.socket

Auditbeat provides useful commands to query the state of the audit system in the Linux kernel.

This module has some configuration options for tuning its behavior. The following example shows all configuration options with their default values.

- module: auditd
  resolve_ids: true
  failure_mode: silent
  backlog_limit: 8192
  rate_limit: 0
  include_raw_message: false
  include_warnings: false
  backpressure_strategy: auto

The audit rules are where you configure the activities that are audited. These rules are configured as either syscalls or files that should be monitored. For example you can track all connect syscalls or file system writes to /etc/passwd.

Auditing a large number of syscalls can place a heavy load on the system so consider carefully the rules you define and try to apply filters in the rules themselves to be as selective as possible.

The kernel evaluates the rules in the order in which they were defined so place the most active rules first in order to speed up evaluation.

You can assign keys to each rule for better identification of the rule that triggered an event and easier filtering later in Elasticsearch.

Defining any audit rules in the config causes Auditbeat to purge all existing audit rules prior to adding the rules specified in the config. Therefore it is unnecessary and unsupported to include a -D (delete all) rule.

auditbeat.modules:
- module: auditd
  audit_rules: |
    # Things that affect identity.
    -w /etc/group -p wa -k identity
    -w /etc/passwd -p wa -k identity
    -w /etc/gshadow -p wa -k identity
    -w /etc/shadow -p wa -k identity

    # Unauthorized access attempts to files (unsuccessful).
    -a always,exit -F arch=b32 -S open,creat,truncate,ftruncate,openat,open_by_handle_at -F exit=-EACCES -F auid>=1000 -F auid!=4294967295 -F key=access
    -a always,exit -F arch=b32 -S open,creat,truncate,ftruncate,openat,open_by_handle_at -F exit=-EPERM -F auid>=1000 -F auid!=4294967295 -F key=access
    -a always,exit -F arch=b64 -S open,truncate,ftruncate,creat,openat,open_by_handle_at -F exit=-EACCES -F auid>=1000 -F auid!=4294967295 -F key=access
    -a always,exit -F arch=b64 -S open,truncate,ftruncate,creat,openat,open_by_handle_at -F exit=-EPERM -F auid>=1000 -F auid!=4294967295 -F key=access

The Auditd module supports the common configuration options that are described under configuring Auditbeat. Here is an example configuration:

auditbeat.modules:
- module: auditd
  # Load audit rules from separate files. Same format as audit.rules(7).
  audit_rule_files: [ '${path.config}/audit.rules.d/*.conf' ]
  audit_rules: |
    ## Define audit rules here.
    ## Create file watches (-w) or syscall audits (-a or -A). Uncomment these
    ## examples or add your own rules.

    ## If you are on a 64 bit platform, everything should be running
    ## in 64 bit mode. This rule will detect any use of the 32 bit syscalls
    ## because this might be a sign of someone exploiting a hole in the 32
    ## bit API.
    #-a always,exit -F arch=b32 -S all -F key=32bit-abi

    ## Executions.
    #-a always,exit -F arch=b64 -S execve,execveat -k exec

    ## External access (warning: these can be expensive to audit).
    #-a always,exit -F arch=b64 -S accept,bind,connect -F key=external-access

    ## Identity changes.
    #-w /etc/group -p wa -k identity
    #-w /etc/passwd -p wa -k identity
    #-w /etc/gshadow -p wa -k identity

    ## Unauthorized access attempts.
    #-a always,exit -F arch=b64 -S open,creat,truncate,ftruncate,openat,open_by_handle_at -F exit=-EACCES -k access
    #-a always,exit -F arch=b64 -S open,creat,truncate,ftruncate,openat,open_by_handle_at -F exit=-EPERM -k access