Most of your questions cannot be answered in a short
manner - and not even unambiguous. Some would say,
that a "real" hacker does not need to develop his/her own tools,
others say, he/she does.

The most brute-force software, that is "testing" the "security" of
your server, is called "penetration testing software" . The two most
well-known (and most used?) are

- nessus[1]
- retina[2]

A guide I just have seen on the web [3].

[1] http://www.nessus.org
[2] http://www.eeye.com/html/Products/Retina/index.html
[3] http://www.penetration-testing.com/