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A common management requirement is that all external Web traffic mu

A common management requirement is that all external Web traffic mu

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A common management requirement is that “all external

Web traffic must flow via the organization’s Web proxy.”

However, that requirement is easier stated than

implemented. Discuss the various problems and issues,

possible solutions, and limitations with supporting this

requirement. In particular, consider issues such as

identifying exactly what constitutes “Web traffic” and how it

may be monitored, given the large range of ports and

various protocols used by Web browsers and servers

Solution

1. All traffic from inside to outside, and vice versa, must

pass through the firewall. This is achieved by physically

blocking all access to the local network except via the

firewall. Various configurations are possible, as explained

later in this section.

2. Only authorized traffic, as defined by the local security

policy, will be allowed to pass. Various types of firewalls

are used, which implement various types of security

policies, as explained later in this section.

3. The firewall itself is immune to penetration. This implies

that use of a trusted system with a secure operating

system.

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Service control:

Determines the types of Internet services that can be

accessed, inbound or outbound. The firewall may filter

traffic on the basis of IP address and TCP port number;

may provide proxy software that receives and interprets

each service request before passing it on; or may host the

server software itself, such as a Web or mail service.

Direction control: Determines the direction in which

particular service requests may be initiated and allowed to

flow through the firewall.

User control: Controls access to a service according to

which user is attempting to access it. This feature is

typically applied to users inside the firewall perimeter

(local users). It may also be applied to incoming traffic

from external users; the latter requires some form of

secure authentication technology, such as is provided in

IPSec.

Behavior control: Controls how particular services are

used. For example, the firewall may filter e-mail to

eliminate spam, or it may enable external access to only a

portion of the information on a local Web server.

1. Because packet filter firewalls do not examine upper-

layer data, they cannot prevent attacks that employ

application-specific vulnerabilities or functions. For

example, a packet filter firewall cannot block specific

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A common management requirement is that “all external Web traffic must flow via the organization’s Web proxy.” However, that requirement is easier stated than implemented. Discuss the various problems and issues, possible solutions, and limitations with supporting this requirement. In particular, consider issues such as identifying exactly what constitutes “Web traffic” and how it may be monitored, given the large range of ports and various protocols used by Web browsers and servers Solution 1. All traffic from inside to outside, and vice versa, must pass through the firewall. This is achieved by physically blocking all access to the local network except via the firewall. Various configurations are possible, as explained later in this section. 2. Only authorized traffic, as defined by the local security policy, will be allowed to pass. Various types of firewalls are used, which implement various types of security policies, as explained later in this section. 3. The firewall itself is immune to penetration. This implies that use of a trusted system with a secure operating system. Service control: Determines the types of Internet services that can be accessed, inbound o ...
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