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Protection against Computer Virus and Malicious Code

A separate host machine may be set up together with the firewall to check for computer viruses and malicious codes in all incoming traffic when going through the firewall. This can centralise the control in updating signatures for computer virus and malicious code, and prevent the computer virus or malicious codes from entering into the web or mail servers.

• Computer virus or malicious code detection measure may also be installed in other positions, such as incorporated with the mail server or the web server to specifically protect individual servers.

• The decision of where to apply computer virus or malicious code detection measure depends on many factors such as network architecture, performance, system or data to be protected and the required protection level. In most cases, mail server should be accommodated with computer virus or malicious code detection measure as usually computer virus/malicious codes come in as email attachments.

Remote Access Servers (RAS) and Modem Pool

A RAS is a special-purpose networking device designed to support remote or mobile computing.

• Authorised users may like to have a dial-in capability, i.e. to access from remote locations without availability of Internet access.
This capability may introduce vulnerabilities, and thus it should be implemented and managed properly.

• A central modem pool is recommended to be used for ease and effectiveness of management and control.
• Authentication mechanism should be used to control remote or dial-in access.

Proxy Servers

A proxy server is a server running simple programs or processes examining packets passed through. It is normally treated as performance enhancing devices for internal network users with value-added security service. It is used as a middleman in which the communications between two sides (e.g. a client and a server) are mediated and destined. That is, each side is communicating with the proxy server instead of directly connecting with the other side. Proxy servers should be configured to provide authorised proxy services and restrict user access to unauthorised destinations. Proxy servers can provide additional support such as caching of recently accessed web pages, access control, logging, content filtering or even address hiding.

Some firewalls can enforce proxy servers for typical services such as TELNET, File Transfer Protocol (FTP), HyperText Transfer Protocol (HTTP) and SMTP, so that no communication can go through the firewall without application level mediation.