Insufficient Privileges When Connect to SYS and SYSTEM
As andba77 suggested, it sounds like a problem with remote password file.  First you need to determine if you have a password file.  It should be on the database server at $ORACLE_HOME/dbs/orapw.  Second is the setting of the init parm 'remote_login_passwordfile'.  If it is set to 'none', no remote logins as sysdba will be allowed.  You can read more about that parameter in the docs at http://docs.oracle.com/cd/E11882_01/server.112/e40402/initparams212.htm#REFRN10184

It would help if we had more detail on the remote connection.  Best and most reliable would be to reproduce the problem with sqlplus at a command prompt, then copy and paste the entire command and the entire response.  Only then can we know exactly what you are doing, and in this particular question "exactly" is important.