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IBM z/OS User exits for the FTP Server must not be used without proper approval and documentation.


Finding ID Version Rule ID IA Controls Severity
V-223632 ACF2-US-000170 SV-223632r533198_rule Medium
In order to prevent unauthorized connection of devices, unauthorized transfer of information, or unauthorized tunneling (i.e., embedding of data types within data types), organizations must disable or restrict unused or unnecessary physical and logical ports/protocols on information systems. Operating systems are capable of providing a wide variety of functions and services. Some of the functions and services provided by default may not be necessary to support essential organizational operations. Additionally, it is sometimes convenient to provide multiple services from a single component (e.g., VPN and IPS); however, doing so increases risk over limiting the services provided by any one component. To support the requirements and principles of least functionality, the operating system must support the organizational requirements, providing only essential capabilities and limiting the use of ports, protocols, and/or services to only those required, authorized, and approved to conduct official business or to address authorized quality of life issues. Several user exit points in the FTP Server component are available to permit customization of its operating behavior. These exits can be used to modify functions such as FTP command usage, client connection controls, post processing tasks, and SMF record modifications. Without proper review and adequate documentation of these exit programs, undesirable operations and degraded security may result. This exposure could lead to unauthorized access impacting data integrity or the availability of some system services, or contribute to the loss of accountability and hamper security audit activities.
IBM z/OS ACF2 Security Technical Implementation Guide 2022-06-22


Check Text ( C-25305r504854_chk )
Refer to the Data configuration file specified on the SYSFTPD DD statement in the FTP started task JCL.

Refer to the file(s) allocated by the STEPLIB DD statement in the FTP started task JCL.

Refer to the libraries specified in the system Linklist and LPA.

If any FTP Server exits are in use, identify them and validate that they were reviewed for integrity and approved by the site AO.

If the following items are in effect for FTP Server user exits, this is not a finding:

The FTCHKCMD, FTCHKIP, FTCHKJES, FTCHKPWD, FTPSMFEX and FTPOSTPR modules are not located in the FTP daemon’s STEPLIB, Linklist, or LPA.

NOTE: The ISPF ISRFIND utility can be used to search the system Linklist and LPA for specific modules.
Fix Text (F-25293r504855_fix)
Review the configuration statements in the FTP.DATA file. Review the FTP daemon STEPLIB, system Linklist, and Link Pack Area libraries. If FTP Server exits are enabled or present, and have not been approved by the site ISSM and not securely written and implemented by the site systems programmer, they should not be installed. Verify that none of the following exits are installed unless they have met the requirements listed above: