% APNIC found the following authoritative answer from: whois.apnic.net

% [whois.apnic.net]
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% Information related to '123.136.68.0 - 123.136.68.255'

% Abuse contact for '123.136.68.0 - 123.136.68.255' is 'ITSS_Network@hq.a-star.edu.sg'

inetnum:        123.136.68.0 - 123.136.68.255
netname:        A-STAR-SG
descr:          Agency for Science, Technology and Research
country:        SG
admin-c:        IN139-AP
tech-c:         IN139-AP
abuse-c:        AA1894-AP
status:         ALLOCATED NON-PORTABLE
mnt-by:         MAINT-A-STAR-SG
mnt-irt:        IRT-A-STAR-SG
last-modified:  2022-05-12T01:55:18Z
source:         APNIC

irt:            IRT-A-STAR-SG
address:        Agency for Science, Technology and Research
address:
address:
address:
e-mail:         ITSS_Network@hq.a-star.edu.sg
abuse-mailbox:  ITSS_Network@hq.a-star.edu.sg
admin-c:        SM2111-AP
tech-c:         SM2111-AP
auth:           # Filtered
remarks:        itss_network@hq.a-star.edu.sg was validated on 2025-12-03
mnt-by:         MAINT-A-STAR-SG
last-modified:  2025-12-03T01:42:50Z
source:         APNIC

role:           ABUSE ASTARSG
country:        ZZ
address:        Agency for Science, Technology and Research
address:
address:
address:
phone:          +000000000
e-mail:         ITSS_Network@hq.a-star.edu.sg
admin-c:        SM2111-AP
tech-c:         SM2111-AP
nic-hdl:        AA1894-AP
remarks:        Generated from irt object IRT-A-STAR-SG
remarks:        itss_network@hq.a-star.edu.sg was validated on 2025-12-03
abuse-mailbox:  ITSS_Network@hq.a-star.edu.sg
mnt-by:         APNIC-ABUSE
last-modified:  2025-12-03T01:43:10Z
source:         APNIC

person:         ITSS Network
address:        30 Biopolis Street
country:        SG
phone:          +65-64074300
e-mail:         ITSS_Network@hq.a-star.edu.sg
nic-hdl:        IN139-AP
mnt-by:         MAINT-A-STAR-SG
last-modified:  2022-05-12T01:54:16Z
source:         APNIC

% Information related to '123.136.64.0/21AS23767'

route:          123.136.64.0/21
origin:         AS23767
descr:          A*STAR
                Agency For Science, Technology And Research
                1 Fusionopolis Way,
                #20-10 Connexis North Tower
mnt-by:         MAINT-A-STAR-SG
last-modified:  2019-02-14T01:10:43Z
source:         APNIC

% This query was served by the APNIC Whois Service version 1.88.34 (WHOIS-AU4)