The defense-in-depth strategy toward security requires system administrators to
take every possible action to improve security. One significant improvement to
security can be obtained by widespread use of encryption. With respect to the
UNIX workstation, the following are security advantages to be gained:
- If a workstation gets compromised and taken over by an attacker, previously encrypted files are likely to be protected. This assumes that passphrases used to encrypt the data are kept in the users memory and not on the workstation.
- By encrypting traffic on the local area network (LAN), the risk of being attacked from a local source is greatly reduced.
Many organizations consider their biggest security feature to be the firewall between the LAN and the Internet. Hower, other workstations on the LAN also pose a significant threat. For example, if the LAN is hubbed, any workstation can listen in on all instant messaging to and from another worksation. Even if the network is switched there are readily available tools, such as ettercap, that can monitor all traffic in and out of a workstation.
- Much of the traffic that travels over the Internet, such as e-mail or FTP, is in the clear or unencrypted. The only protection afforded to this traffic is security through obscurity. In other words, the telnet, e-mail, and FTP traffic can be read in many places as the traffic is routed, but who would want to? Most users would not find this level of security very comforting.