A few general questions about security ...

[hixe]

Dear Experts!
Please answer on several question relating to security:
1) Which problems with security appear most often?
2) What does cause such problems?
3) What are consequences of problems with security system?
4) What kind of security do you mean is the best?
Thant you very much,
Hezer.

[r2d2]

I believe most cases of security breaches are from passwords being found out and used rather than brute force type method.

Keep ur passwords safe!

Im sure there are a few security tutorials around the web too.

[tomek]

Top Vulnerabilities in Web Applications:
http://www.owasp.org/documentation/topten

how do avoid these problemes:
http://www.owasp.org/documentation/guide (download the OWASP Guide)

[Kyle]

hixe - Please be more specific as to how your questions apply to your situation. Let us know what operating system you're referring to, whether you're refering to a server you want to start, or if this just applies to website security?

Your questions are important, but it really depends on a few specifics. People could probably help you best if you let us know a little more.