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Chapter 8. Checking integrity with AIDE

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Advanced Intrusion Detection Environment (AIDE) is a utility that creates a database of files on the system, and then uses that database to ensure file integrity and detect system intrusions.

8.1. Installing AIDE

To start file-integrity checking with AIDE, you must install the corresponding package and initiate the AIDE database.

Prerequisites

  • The AppStream repository is enabled.

Procedure

  1. Install the aide package:

    # dnf install aide
  2. Generate an initial database:

    # aide --init
    Start timestamp: 2024-07-08 10:39:23 -0400 (AIDE 0.16)
    AIDE initialized database at /var/lib/aide/aide.db.new.gz
    
    Number of entries:	55856
    
    ---------------------------------------------------
    The attributes of the (uncompressed) database(s):
    ---------------------------------------------------
    
    /var/lib/aide/aide.db.new.gz
    …
      SHA512   : mZaWoGzL2m6ZcyyZ/AXTIowliEXWSZqx
                 IFYImY4f7id4u+Bq8WeuSE2jasZur/A4
                 FPBFaBkoCFHdoE/FW/V94Q==
  3. Optional: In the default configuration, the aide --init command checks just a set of directories and files defined in the /etc/aide.conf file. To include additional directories or files in the AIDE database, and to change their watched parameters, edit /etc/aide.conf accordingly.
  4. To start using the database, remove the .new substring from the initial database file name:

    # mv /var/lib/aide/aide.db.new.gz /var/lib/aide/aide.db.gz
  5. Optional: To change the location of the AIDE database, edit the /etc/aide.conf file and modify the DBDIR value. For additional security, store the database, configuration, and the /usr/sbin/aide binary file in a secure location such as a read-only media.

8.2. Performing integrity checks with AIDE

You can use the crond service to schedule regular file-integrity checks with AIDE.

Prerequisites

  • AIDE is properly installed and its database is initialized. See Installing AIDE

Procedure

  1. To initiate a manual check:

    # aide --check
    Start timestamp: 2024-07-08 10:43:46 -0400 (AIDE 0.16)
    AIDE found differences between database and filesystem!!
    
    Summary:
      Total number of entries:	55856
      Added entries:		0
      Removed entries:		0
      Changed entries:		1
    
    ---------------------------------------------------
    Changed entries:
    ---------------------------------------------------
    
    f   ...      ..S : /root/.viminfo
    
    ---------------------------------------------------
    Detailed information about changes:
    ---------------------------------------------------
    
    File: /root/.viminfo
      SELinux  : system_u:object_r:admin_home_t:s | unconfined_u:object_r:admin_home
                 0                                | _t:s0
    …
  2. At a minimum, configure the system to run AIDE weekly. Optimally, run AIDE daily. For example, to schedule a daily execution of AIDE at 04:05 a.m. by using the cron command, add the following line to the /etc/crontab file:

     05 4 * * * root /usr/sbin/aide --check

Additional resources

  • cron(8) man page on your system

8.3. Updating an AIDE database

After verifying the changes of your system, such as package updates or configuration files adjustments, update also your baseline AIDE database.

Prerequisites

  • AIDE is properly installed and its database is initialized. See Installing AIDE

Procedure

  1. Update your baseline AIDE database:

    # aide --update

    The aide --update command creates the /var/lib/aide/aide.db.new.gz database file.

  2. To start using the updated database for integrity checks, remove the .new substring from the file name.

8.4. File-integrity tools: AIDE and IMA

Red Hat Enterprise Linux provides several tools for checking and preserving the integrity of files and directories on your system. The following table helps you decide which tool better fits your scenario.

Table 8.1. Comparison between AIDE and IMA
QuestionAdvanced Intrusion Detection Environment (AIDE)Integrity Measurement Architecture (IMA)

What

AIDE is a utility that creates a database of files and directories on the system. This database serves for checking file integrity and detect intrusion detection.

IMA detects if a file is altered by checking file measurement (hash values) compared to previously stored extended attributes.

How

AIDE uses rules to compare the integrity state of the files and directories.

IMA uses file hash values to detect the intrusion.

Why

Detection - AIDE detects if a file is modified by verifying the rules.

Detection and Prevention - IMA detects and prevents an attack by replacing the extended attribute of a file.

Usage

AIDE detects a threat when the file or directory is modified.

IMA detects a threat when someone tries to alter the entire file.

Extension

AIDE checks the integrity of files and directories on the local system.

IMA ensures security on the local and remote systems.

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