System Administration Guide: Security Services

Basic Audit Reporting Tool (Overview)

BART is a file tracking tool that operates entirely at the file system level. Using BART gives you the ability to quickly, easily, and reliably gather information about the components of the software stack that is installed on deployed systems. Using BART can greatly reduce the costs of administering a network of systems by simplifying time-consuming administrative tasks.

BART enables you to determine what file-level changes have occurred on a system, relative to a known baseline. You use BART to create a baseline or control manifest from a fully installed and configured system. You can then compare this baseline with a snapshot of the system at a later time, generating a report that lists file-level changes that have occurred on the system since it was installed.

The bart command is a standard UNIX command. You can redirect the output of the bart command to a file for later processing.

BART Features

BART has been designed with an emphasis on a simple syntax that is both powerful and flexible. The tool enables you to generate manifests of a given system over time. Then, when the system's files need to be validated, you can generate a report by comparing the old and new manifests. Another way to use BART is to generate manifests of several similar systems and run system-to-system comparisons. The main difference between BART and existing auditing tools is that BART is flexible, both in terms of what information is tracked and what information is reported.

Additional benefits and uses of BART include the following:

BART Components

BART has two main components and one optional component:

BART Manifest

You use the bart create command to take a file-level snapshot of a system at a particular time. The output is a catalog of files and file attributes called a manifest. The manifest lists information about all the files or specific files on a system. It contains information about attributes of files, which can include some uniquely identifying information, such as an MD5 checksum. For more information about the MD5 checksum, see the md5(3EXT) man page. A manifest can be stored and transferred between client and server systems.

Note –

BART does not cross file system boundaries, with the exception of file systems of the same type. This constraint makes the output of the bart create command more predictable. For example, without arguments, the bart create command catalogs all ZFS file systems under the root (/) directory. However, no NFS or TMPFS file systems or mounted CD-ROMs would be cataloged. When creating a manifest, do not attempt to audit file systems on a network. Note that using BART to monitor networked file systems can consume large resources to generate manifests that will have little value.

For more information about BART manifests, see BART Manifest File Format.

BART Report

The report tool has three inputs: the two manifests to be compared and an optional user-provided rules file that indicates which discrepancies are to be flagged.

You use the bart compare command to compare two manifests, a control manifest and a test manifest. These manifests must be prepared with the same file systems, options, and rules file that you use with the bart create command.

The output of the bart compare command is a report that lists per-file discrepancies between the two manifests. A discrepancy is a change to any attribute for a given file that is cataloged for both manifests. Additions or deletions of file entries between the two manifests are also considered discrepancies.

There are two levels of control when reporting discrepancies:

These levels of control are intentional, since generating a manifest is more costly than reporting discrepancies between two manifests. Once you have created manifests, you have the ability to compare manifests from different perspectives by running the bart compare command with different rules files.

For more information about BART reports, see BART Reporting.

BART Rules File

The rules file is a text file that you can optionally use as input to the bart command. This file uses inclusion and exclusion rules. A rules file is used to create custom manifests and reports. A rules file enables you to express in a concise syntax which sets of files you want to catalog, as well as which attributes to monitor for any given set of files. When you compare manifests, the rules file aids in flagging discrepancies between the manifests. Using a rules file is an effective way to gather specific information about files on a system.

You create a rules file by using a text editor. With a rules file, you can perform the following tasks:

Note –

You can create several rules files for different purposes. However, if you create a manifest by using a rules file, you must use the same rules file when you compare the manifests. If you do not use the same rules file when comparing manifests that were created with a rules file, the output of the bart compare command will list many invalid discrepancies.

A rules file can also contain syntax errors and other ambiguous information as a result of user error. If a rules file does contain misinformation, these errors will also be reported.

Using a rules file to monitor specific files and file attributes on a system requires planning. Before you create a rules file, decide which files and file attributes on the system you want to monitor. Depending on what you are trying to accomplish, you might use a rules file to create manifests, compare manifests, or for purposes.

For more information about the BART rules file, see BART Rules File Format and the bart_rules(4) man page.