Viruses and other malware often exploit bugs known as buffer

Viruses and other malware often exploit bugs known as buffer overflows in widely used software. One method of preventing these exploits in software running on current Windows versions is Data Execution Prevention (DEP).  

investigate buffer overflows and DEP. 

• How does DEP prevent malicious      attacks via buffer overflows? 
• Is it always effective? 
• Why might a user or      administrator disable DEP?