audit(5)

User and Event Selection

The auditing system provides administrators with a mechanism to select users and activities to be audited. Users are assigned unique identifiers called audit ids by the administrator which remain unchanged throughout a user's history. The audusr(1M) command is used to specify those users who are to be audited. The audevent(1M) command is used to specify system activities (auditable events) that are to be audited. Auditable events are classified into several categories. An event category consists of a set of operations that affect a particular aspect of the system. For an event category list, see audevent(1M).

Self-auditing Programs

To reduce the amount of log data and to provide a higher-level recording of some typical system operations, a collection of privileged programs are given capabilities to perform self-auditing. This means that the programs can suspend the currently specified auditing on themselves and produce a high-level description of the operations they perform. These self-auditing programs include: at(1), chfn(1), chsh(1), crontab(1), login(1), newgrp(1), passwd(1), audevent(1M), audisp(1M), audsys(1M), audusr(1M), cron(1M), groupadd(1M), groupdel(1M), groupmod(1M), init(1M), lpsched(1M), sam(1M), useradd(1M), userdel(1M), and usermod(1M).

Most of these commands generate audit data under a single event category. For example, sam(1M) generates the audit data under the event admin. Other commands may generate data under multiple event categories. For example, init(1M) generates data under the events login and admin.

Viewing of Audited Data

The audisp(1M) command is used to view audited data recorded in log files. audisp(1M) merges the log files into a single audit trail in chronological sequence. The administrator can select viewing criteria provided by audisp(1M) to limit the search to particular kinds of events which the administrator is interested in investigating.

Monitoring the Auditing System

To ensure that the auditing system operates normally and that any abnormal behaviors are detected, a privileged daemon program, audomon(1M), runs in the background to monitor various auditing system parameters. When these parameters take on abnormal (dangerous) values, or when components of the auditing system are accidentally removed, audomon(1M) prints warning messages and tries to resolve the problem if possible.

Starting and Halting the Auditing System

The administrator can use the audsys(1M) command to start or halt the auditing system, or to get a brief summary of the status of the audit system. Prior to starting the auditing system, audsys(1M) also validates the parameters specified, and ensures that the auditing system is in a safe and consistent state.

Audit Log Files

At any time when the auditing system is enabled, at least an audit log file must be present, and another back-up log file is highly recommended. Both of these files (along with various attributes for these files) can be specified using audsys(1M). When the current log file exceeds a pre-specified size, or when the auditing file system is dangerously full, the system automatically switches to the back-up file if possible. If a back-up log file is not available, warning messages are sent to request appropriate administrator action.