/usr/lib/nagios/ is in nagios-snmp-plugins 1.1.1-7.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/nagios/plugins/
/usr/lib/nagios/plugins/check_snmp_boostedge.pl
/usr/lib/nagios/plugins/check_snmp_cpfw.pl
/usr/lib/nagios/plugins/check_snmp_css.pl
/usr/lib/nagios/plugins/check_snmp_css_main.pl
/usr/lib/nagios/plugins/check_snmp_env.pl
/usr/lib/nagios/plugins/check_snmp_int.pl
/usr/lib/nagios/plugins/check_snmp_linkproof_nhr.pl
/usr/lib/nagios/plugins/check_snmp_load.pl
/usr/lib/nagios/plugins/check_snmp_mem.pl
/usr/lib/nagios/plugins/check_snmp_nsbox.pl
/usr/lib/nagios/plugins/check_snmp_process.pl
/usr/lib/nagios/plugins/check_snmp_storage.pl
/usr/lib/nagios/plugins/check_snmp_vrrp.pl
/usr/lib/nagios/plugins/check_snmp_win.pl