/usr/include/net-snmp/library/snmpv3-security-includes.h is in libsnmp-dev 5.7.3+dfsg-1.8ubuntu3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 | /* This file is automatically generated by configure. Do not modify by hand. */
#include <net-snmp/library/snmpusm.h>
|