To see jobs and statuses we can query "dba_datapump_jobs" view:

SELECT owner_name, job_name, state
FROM dba_datapump_jobs;

set lines 150 pages 100
col program for a20
col username for a5
col spid for a7
col job_name for a25
select to_char(sysdate,'YYYY-MM-DD HH24:MI:SS') "DATE", s.program, s.sid,
    s.status, s.username, d.job_name, p.spid, s.serial#, p.pid
from v$session s, v$process p, dba_datapump_sessions d
where p.addr=s.paddr and s.saddr=d.saddr;


To attach to a data pump job run the following command from a cmd prompt:

If an expdp job:
expdp USER/PASSWORD ATTACH=job_name
expdp '/ as sysdba' ATTACH=Job_name

If an impdp job:
impdp USER/PASSWORD ATTACH=job_name
impdp '/ as sysdba' ATTACH=Job_name

Once you are attached to a job, you can execute :
KILL_JOB
STOP_JOB=IMMEDIATE
STOP_JOB

Stopped job can be restarted but not killed ones...