An administrator can also give a user or group of users all three permissions.
A firewall is a device that can monitor access into a network or individual computer. There are several types of firewall techniques. There is packet filtering where the firewall is what decides whether to allow data to pass through it or deny it based on a set of predefined rules. Another type is an application gateway where security mechanisms are applied to specific applications like FTP and Telnet services. Also, there is a circuit level gateway where security mechanisms are applied to TCP or UDP connections. Once the connection is made packets can flow without any further checking. The last technique is proxy server where all network messages are intercepted and the true network address is hidden. Firewalls can be implemented in both hardware and software, or a combination of both. A firewall is considered a first line of defense in protecting private information. .
Although both of these techniques are proactive, they have obvious differences. File security can protect users or groups of users from accessing files by administrating permissions to each file stored within the network. A firewall prevents data from leaving or entering the entire network. Both of these techniques have their places within a network. .
Secret, Public, Symmetrical and Asymmetrical Keys.
There are two basic types of encryption in use today. The first is called private key, which is known as a single or symmetrical key, and the other is known as secret key encryption and public or asymmetrical key encryption. With symmetrical encryption, the same key is used for both encryption and decryption. The key is kept secret so that unauthorized parties cannot complete the decryption process because the key should never be disclosed, hence the name "secret key". Asymmetrical encryption solves the problem of maintaining key security by having separate keys for encryption and decryption, which uniquely match each other, but are not predictable from each other.