HP OpenVMS Guide to System Security: OpenVMS Version 8.4 > Chapter 4 Protecting Data
Whenever a process uses an object or modifies its security profile (see “Modifying a Security Profile”), the system can send an alarm to an operator terminal or write a message to the audit log file. By reading the log file, a security administrator can review system activity to see how protected objects are being used, when they are being used, and who is using them.
Exactly which type of information is reported through the auditing system depends on how the security administrator defines the site's requirements. If system administrators choose to have object use audited, they can enable auditing for the appropriate categories of events.
The operating system can filter security-related events and send system administrators messages only when objects are accessed in certain ways. Sites are often more interested in the privileged use of a file or the failure to access a file than in every file access. Such a site can request auditing messages whenever a process fails in accessing a file, but not when it is successful. The system can report how the process exercised, or failed to exercise, the right to access the object in the first place: through a protection code, an ACE, or a privilege.
Each object class has its own auditing profile, described in “Descriptions of Object Classes”, and so it is possible to receive more information on some classes of objects than on others. For any object, the system can send an auditing message whenever a user or application accesses the object or modifies its security elements. In some instances, the system can send a notification when a process creates an object, stops using it or deletes it.
When you are auditing object access events, keep in mind that the operating system may check a user's right to an object several times during a single operation. A file operation, for example, can involve checks for both directory and file access. Before a user deletes a file, the system checks for delete access to the file and write access to the directory.
For this reason, it is best for a security administrator to enable auditing for all types of object access events. For example, to track all instances where a user tries to access a file but fails, a security administrator would use the /ENABLE=ACCESS=FAILURE=ALL qualifier to the SET AUDIT command.
For object classes that support deaccess auditing (for example, the file class), once a process gains access to an object, the system does not audit subsequent access attempts to the object unless the process attempts an operation that is incompatible with the access modes previously granted. When this occurs, the system performs an additional protection check that is audited. This access window continues until the object is deaccessed (for example, the file is closed).
Rather than audit an entire class of objects, security administrators and users with control access to an object can single out a specific object for auditing by attaching an Alarm or Audit ACE to it (see “Adding Access Control Entries to Sensitive Files”). Although you can add an auditing ACE to any file that you own or have control access to, it is best to consult your security administrator before doing so. As with object classes, the security administrator has to enable the ACL auditing category before any auditing messages are generated.