Guidelines on Securing Public Web Servers

8.  Implementing a Secure Network for a Web Server  

The network infrastructure that supports the Web server plays a critical role in the security of 

the Web server.  In most configurations, the network infrastructure will be the first line of 

defense between the Internet and a public Web server.  Although considerations of network 

infrastructure are influenced by many factors other than security (e.g., cost, performance, and 

reliability), this section will primarily address security issues.   

Network design alone, however, cannot protect a Web server.  The frequency, sophistication, 

and even variety of Web attacks perpetrated today support the idea that Web security must be 

implemented through layered and diverse defense mechanisms (defense in depth).  This 

section discusses those network components that can support and protect Web servers to 

further enhance their overall security.  

8.1 Network 

Location 

An organization has many choices when selecting a networking location, and security may not 

be the principal factor in deciding between those options.  Network location is the first and in 

many respects most critical networking decision that affects Web server security.  Network 

location is important for several reasons.  Network location determines what network 

infrastructure can be used to protect the Web server.  For example, if the Web server is located 

behind the organization's firewall, then the firewall cannot be used to control traffic to and 

form the internal network and the Web server.  Network location also determines what other 

portions of the network are vulnerable if the Web server is compromised.  For example, if the 

Web server is located on the internal production network, then the internal network is subject 

to attack from the compromised Web server.  An organization may choose not to have the 

Web server located on its network at all and to outsource the hosting to a third party.   

8.1.1  Unadvisable Network Locations  

Some organizations choose to locate their public Web servers on their internal production 

networks, that is, they locate their Web server on the same network as their internal users and 

servers.  This location is not recommended because it exposes the internal network to 

unnecessary risk of compromise.  The principal weakness of this configuration is that Web 

servers are often the target of choice for attackers.  If they manage to compromise the Web 

server, they will be on the internal network and can more easily compromise internal hosts.   

Another network location that is not generally recommended is placing the Web server before 

an organization's firewall or router that provides IP filtering.  In this type of the configuration 

the network can provide little, if any, protection to the Web server.  All security has to be 

provided by the Web server itself, which provides a single point of failure.  To be even 

somewhat secure in this location, the Web server operating system and application has to be 

well hardened (all unnecessary and insecure services disabled) and with all necessary security 

patches applied.  To maintain the  security  of the setup, the Web administrator must stay up 

to date on all vulnerabilities and related patches.  Another limitation of this location is that it is 

difficult in this type of configuration to provide any sort of secure remote administration or 

content update capability.   

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