Date Added: Jan 2011
Modern computer systems are under attack, making computer security an important topic to understand. Malicious people (called hackers or attackers) search for computer systems (hosts) that are vulnerable to attacks. Vulnerable hosts range from Personal Computers (PCs) used in a home environment to corporate networks that are professionally managed and maintained by system administrators. A computer system becomes a vulnerable host when it contains mistakes or errors that can be exploited by attackers to achieve unauthorized access. For example, an attacker can gain unauthorized access to a PC if a user clicks on a malicious email attachment, or an attacker can gain access to a system if an application running on the host contains a software programming error (vulnerability) that the hacker can exploit.