Access attacks exploit known vulnerabilities in authentication services, FTP services, and web services to gain entry to web accounts, confidential databases, and other sensitive information. An access attack allows an individual to gain unauthorized access to information that they have no right to view. Access attacks can be classified into four types. One of the most common types of access attacks is the password attack. Password attacks can be implemented using a packet sniffer to yield user accounts and passwords that are transmitted as clear text. Password attacks can also refer to repeated attempts to log in to a shared resource, such as a server or router, to identify a user account, password, or both. These repeated attempts are called dictionary attacks or brute-force attacks.
Click the buttons in the figure to see examples of access attacks.