The IBM z/OS system must use a time protocol that syncs with an authoritative external time source.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
medium	V-223552	SRG-OS-000355-GPOS-00143	ACF2-OS-000160	SV-223552r1169917_rule	2025-12-15	9

Description
Inaccurate time stamps make it more difficult to correlate events and can lead to an inaccurate analysis. Determining the correct time a particular event occurred on a system is critical when conducting forensic analysis and investigating system events. Sources outside the configured acceptable allowance (drift) may be inaccurate. Synchronizing internal information system clocks provides uniformity of time stamps for information systems with multiple system clocks and systems connected over a network. Organizations should consider endpoints that may not have regular access to the authoritative time server (e.g., mobile, teleworking, and tactical endpoints).

Description

Inaccurate time stamps make it more difficult to correlate events and can lead to an inaccurate analysis. Determining the correct time a particular event occurred on a system is critical when conducting forensic analysis and investigating system events. Sources outside the configured acceptable allowance (drift) may be inaccurate. Synchronizing internal information system clocks provides uniformity of time stamps for information systems with multiple system clocks and systems connected over a network. Organizations should consider endpoints that may not have regular access to the authoritative time server (e.g., mobile, teleworking, and tactical endpoints).

ℹ️ Check
Verify the operating system, for networked systems, compares internal information system clocks at least every 24 hours with a server synchronized to one of the redundant United States Naval Observatory (USNO) time servers, or a time server designated for the appropriate DOD network (NIPRNet/SIPRNet), and/or the Global Positioning System (GPS). If it does not, this is a finding.

✔️ Fix
Coordinate with system staff to determine the best time protocols available for the z/OS systems at the site. SNT is one protocol available. Obtain a copy of this sample procedure from SEZAINST and store it in one of the PROCLIB concatenation data sets. Perform the following to start SNTPD as a procedure: Invoke the procedure using the system operator start command. The following sample, SEZAINST(SNTPD), shows how to start SNTPD as a procedure: //* //* Sample procedure for the Simple Network Time Protocol (SNTP) //* //* z/OS Communications Server Version 1 Release 13 //* SMP/E Distribution Name: SEZAINST(EZASNPRO) //* //* Copyright: Licensed Materials - Property of IBM //* 5650-ZOS //* Copyright IBM Corp. 2002, 2015 //* //* Status: CSV2R2 //* //SNTPD EXEC PGM=SNTPD,REGION=4096K,TIME=NOLIMIT, //PARM='/ -d' //SYSPRINT DD SYSOUT=,DCB=(RECFM=F,LRECL=132,BLKSIZE=132) //SYSIN DD DUMMY //SYSERR DD SYSOUT= //SYSOUT DD SYSOUT=,DCB=(RECFM=F,LRECL=132,BLKSIZE=132) //CEEDUMP DD SYSOUT= //SYSABEND DD SYSOUT=*

✔️ Fix

Coordinate with system staff to determine the best time protocols available for the z/OS systems at the site. SNT is one protocol available. Obtain a copy of this sample procedure from SEZAINST and store it in one of the PROCLIB concatenation data sets. Perform the following to start SNTPD as a procedure: Invoke the procedure using the system operator start command. The following sample, SEZAINST(SNTPD), shows how to start SNTPD as a procedure: //* //* Sample procedure for the Simple Network Time Protocol (SNTP) //* //* z/OS Communications Server Version 1 Release 13 //* SMP/E Distribution Name: SEZAINST(EZASNPRO) //* //* Copyright: Licensed Materials - Property of IBM //* 5650-ZOS //* Copyright IBM Corp. 2002, 2015 //* //* Status: CSV2R2 //* //SNTPD EXEC PGM=SNTPD,REGION=4096K,TIME=NOLIMIT, //PARM='/ -d' //SYSPRINT DD SYSOUT=*,DCB=(RECFM=F,LRECL=132,BLKSIZE=132) //SYSIN DD DUMMY //SYSERR DD SYSOUT=* //SYSOUT DD SYSOUT=*,DCB=(RECFM=F,LRECL=132,BLKSIZE=132) //CEEDUMP DD SYSOUT=* //SYSABEND DD SYSOUT=*