How to restrict data pump logon to localhost
ADMINISTER DATABASE TRIGGER Privilege Causes Logon Trigger to Skip Errors (Doc ID 265012.1)

ADMINISTER DATABASE TRIGGER Privilege Behavior with Database Logon Trigger
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Logon triggers can be used to mediate database access: when the restrictive 
conditions are not met, an application error with a message is raised that 
causes the logon to be denied.

...

However, we need to keep at least one user who can still connect when there is 
a problem : a fallback mechanism must exist where an administrative user is 
exempt from such errors of a prohibited connection. 

Any user granted the ADMINISTER DATABASE TRIGGER system privilege can still 
connect : instead of getting the error causing the session to be terminated, 
the error is recorded in the alert.log and a trace file in user_dump_dest.


And:

select * from dba_sys_privs where privilege = 'ADMINISTER DATABASE TRIGGER';

GRANTEE                        PRIVILEGE                                ADM
------------------------------ ---------------------------------------- ---
WMSYS                          ADMINISTER DATABASE TRIGGER              NO 
DBA                            ADMINISTER DATABASE TRIGGER              YES
SYS                            ADMINISTER DATABASE TRIGGER              NO 
IMP_FULL_DATABASE              ADMINISTER DATABASE TRIGGER              NO 


So yes, you can try local OS authentication.