- Overview
- Firewall Review
- Static Firewall
- Stateful Firewall
- The Internet Connection Firewall
- Enabling & Disabling the ICF
- Services Options
- Adding a Service
- Programs Options
- Security Logging Options
- Setting up Security Logging
- ICMP Options
- Adjusting the ICMP Options
- Understanding the ICMP options
- Issues to clarify before enabling Internet Connection Sharing
- Enabling / Adjusting / Disabling Internet Connection Sharing
- Summary of the ICF
This chapter is from the book
This chapter is from the book
This chapter is from the book
Services Options
In the case that the ICF is enabled, but there are web services that need to be allowed to pass through the firewall, the default settings of the ICF are not acceptable. For situations like this, Microsoft has included the ability to allow data belonging to specific services to pass through the firewall. Not only does the ICF have the ability to enable or disable designated services, but it comes preloaded with a selection of the more typical web services that a user might need.
CAUTION
Avoid enabling extra services unless they are necessary. Each service increases the chance of penetration.
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Fig. 5-6The following defines each of the default services:
FTP Server:
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Port: 21
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Protocol: TCP
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Purpose: The typical FTP server exists to hold files and provide Internet users with the ability to transfer files from server to client or vise versa
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Example: Microsoft uses an FTP server to host its free web browser program (Internet Explorer) that the general public can download and install
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Internet Mail Access Protocol Version 3 (IMAP3)
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Port: 220
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Protocol: TCP
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Purpose: Software that allows users to retrieve email messages. Allows one user to access multiple mailboxes or folders on the Mail Server
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Example: Microsoft's Exchange Server
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Internet Mail Access Protocol Version 4 (IMAP4)
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Port: 143
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Protocol: TCP
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Purpose: Software that allows users to retrieve email messages. Same as IMAP3 with the addition of new features such as search ability.
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Example: Microsoft Exchange Server
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Internet Mail Server (SMTP)
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Port: 25
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Protocol: TCP
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Purpose: Software that allows users to send email messages. Typically used by ISP's, an SMTP Email Server is used by clients to send emails. Used in conjunction with POP3 Email server.
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Example: Sendmail (*nix Email program)
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Post-Office Protocol Version 3 (POP3)
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Port: 110
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Protocol: TCP
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Purpose: Software that allows users to retrieve messages from one email account (folder) at a time. Used by businesses and ISP's in conjunction with SMTP server.
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Example: Sendmail (*nix Email program)
Remote Desktop
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Port: 3389
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Protocol: TCP
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Purpose: Software used to allow a user to access their computer from a remote computer. Often used in work environments to allow users the ability to work from home.
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Example: Microsoft's Remote Desktop Software
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Secure Web Server (HTTPS)
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Port: 443
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Protocol: TCP
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Purpose: Software use to create a secure connection between client and host to pass sensitive data (e.g. credit cards, social security information) securely.
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Example: An online store that uses SSL to encrypt the sales information send from client to server.
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Telnet Server
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Port: 23
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Protocol: TCP
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Purpose: Software used to allow one or more remote users access to a host computer. Typically used in *nix environments to provide users with the ability to work from home or remotely from the central server.
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Example: Colleges often use Telnet servers to permit students access to email, programs, and other required information as their educational courses require.
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Web Server (HTTP)
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Port: 80
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Protocol: TCP
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Purpose: Software used to package and ship web pages from host computer to client computer.
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Example: Microsoft's Internet Personal Web server software that is included which is provided in all editions of Windows XP and will allow an owner to set up a personal web site on their computer.
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