SPL and then recompiling and linking the program to create a new load module that incorporates the changed code therefore the SPL is a sensitive are which to preserve application integrity must be properly controlled
The worst-case situation no controls
Figure 5.12 shows the SPL without controls this arrangement has the potential to create the following two serious forms of exposure (see the following list)
1 access to program is completely unrestricted programmers and others can access any programs stored in the library and there is no provision for detecting an unauthorized intrusion
2 because of these control weakness programs are subject to unauthorized changes hence there is no basis for relying on the effectiveness of other controls In other words with no provision for detecting unauthorized access to the SPL program integrity cannot be verified
Control is always in conflict with operational flexibility and efficiency for these reasons systems professionals who must work daily within this environment sometimes oppose controlling the SPL to achieve a mutually acceptable control – flexibility trade-off between the needs of systems professionals and auditor both must understand the exposures that are created when control features are not employed or are routinely circumvented in spite of the exposure just described the no-controls approach is often the choice that management makes
A Controlled SPL environment
To control the SPL protective features and procedures must be explicitly addressed and this requires the implementation of an SPL management system(SPLMS) figure 5.13 illustrates the use of this technique the black box surrounding the SPL signifies the SPLMS. This software is used to control four routine but critical functions (1) storing program on the SPL (2) retrieving programs for maintenance purposes (3) deleting obsolete programs from the library and (4) documenting program changes to provide an audit trail of the changes by the computer manufacturer as part of the operating system or may be purchased through software vendors. Some organizations to provide special control features develop their own SPL soft ware
The mere presence of an SPLMS does not guarantee program integrity Again we can draw an analogy with the DBMS to achieve data integrity the DBMS must be properly used; control does not come automatically it must be planned
Password control assigning passwords provides one form of access control over the SPL this is similar to password controls used in a DBMS to protect data files. As more authorized personnel have a need to know the password the potential for losing control of the password increases since responsibility for the secrecy of a shared