The common misconception about computer security related problems in today's age is that the Hackers are the ones responsible for Security holes. This should in fact be corrected, for dangerous security holes would not exist if it were not for the programmer of the vulnerable application creating a weakness that could be exploited. Usually the programmer does this by accident out of lack of care or out of ignorance, or even perhaps just a simple place where he or she "missed a spot".
Many times vulnerabilities are also the result of Network Administrators, either for configuring a system with a configuration that is known to be insecure, for installing vulnerable applications themselves, or for ignorance and/or laziness. When systems go un-patched, they become more and more vulnerable. This is also the Administrator's fault. Sometimes, in fact, administrators are tricked into giving away a password by a phone call from the remote attacker himself, which introduces Social Engineering.
This assumes that you have a basic understanding of most generic MS-DOS. A quick reference of commands can be found here; however typing the command name with -help after the command may help you a bit more. This also assumes that you have a basic understanding of MS-DOS, FTP, HTTP, MSSQL, NetBIOS, and mmc.exe, see all attached links for references.
Most of the code within Security 101 will not actually work. It has been abridged for readability as well as optimal learning speed.