1. Different ways to guess Oracle database SID:

http://www.dsecrg.com/files/pub/pdf/Different_ways_to_guess_Oracle_database_SID_%28eng%29.pdf

2. TNS Listener poison

http://www.rapid7.com/db/modules/auxiliary/scanner/oracle/tnspoison_checker

3. Remote stealth pass brute force

https://www.exploit-db.com/exploits/22069/

4. Oracle database attacking tool

https://github.com/quentinhardy/odat

5. Oracle security papers

http://www.petefinnigan.com/orasec.htm

http://www.davidlitchfield.com/