ZyXEL Communications P-660HW-T - V2, Руководство пользователя

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P-660HW-T v2 User’s Guide
Chapter 9 Firewalls 147
• Encourage your company or organization to develop a comprehensive security plan.
Good network administration takes into account what hackers can do and prepares
against attacks. The best defense against hackers and crackers is information. Educate all
employees about the importance of security and how to minimize risk. Produce lists like
this one!
• DSL or cable modem connections are “always-on” connections and are particularly
vulnerable because they provide more opportunities for hackers to crack your system.
Turn your computer off when not in use.
• Never give out a password or any sensitive information to an unsolicited telephone call or
e-mail.
• Never e-mail sensitive information such as passwords, credit card information, etc.,
without encrypting the information first.
• Never submit sensitive information via a web page unless the web site uses secure
connections. You can identify a secure connection by looking for a small “key” icon on
the bottom of your browser (Internet Explorer 3.02 or better or Netscape 3.0 or better). If
a web site uses a secure connection, it is safe to submit information. Secure web
transactions are quite difficult to crack.
• Never reveal your IP address or other system networking information to people outside
your company. Be careful of files e-mailed to you from strangers. One common way of
getting BackOrifice on a system is to include it as a Trojan horse with other files.
• Change your passwords regularly. Also, use passwords that are not easy to figure out.
The most difficult passwords to crack are those with upper and lower case letters,
numbers and a symbol such as % or #.
• Upgrade your software regularly. Many older versions of software, especially web
browsers, have well known security deficiencies. When you upgrade to the latest
versions, you get the latest patches and fixes.
• If you use “chat rooms” or IRC sessions, be careful with any information you reveal to
strangers.
• If your system starts exhibiting odd behavior, contact your ISP. Some hackers will set off
hacks that cause your system to slowly become unstable or unusable.
• Always shred confidential information, particularly about your computer, before
throwing it away. Some hackers dig through the trash of companies or individuals for
information that might help them in an attack.
9.7 Packet Filtering Vs Firewall
Below are some comparisons between the ZyXEL Device’s filtering and firewall functions.
9.7.1 Packet Filtering:
• The router filters packets as they pass through the router’s interface according to the filter
rules you designed.
• Packet filtering is a powerful tool, yet can be complex to configure and maintain,
especially if you need a chain of rules to filter a service.
• Packet filtering only checks the header portion of an IP packet.