Internet is vulnerable to flaws and weaknesses in the network defence. Vulnerabilities may result from bugs or design flaws in the system. Some vulnerabilities are caused by un-sanitized user input, often allowing the direct execution of commands or SQL statements. Sometimes the programmer fails to check the size of data buffers, which can overflow and cause corruption of the stack or heap areas of memory.
Vulnerability usually allows an attacker to trick the application into bypassing access control checks or executing commands on the system hosting the application.
There are a number of vulnerabilities that your computer and network may be subjected to. Some of the most common ones are input validation errors like format string bugs, improperly handling of shell metacharacters so they are interpreted, SQL injection and in web applications cross-site scripting. Also stack smashing and other buffer overflows as well as symlink races are common vulnerabilities.
Vulnerability scans
Vulnerabilities might exist in all major operating systems like Windows, Mac OS, Linux, OpenVMS, and others. The vulnerability of your network and servers can be tested by vulnerability scans. They test your servers, web pages, firewall and others for possible vulnerability. Vulnerability scans can be downloaded from the Internet.