ZyXEL Communications Prestige 652, User Manual, Page: 145 / 521

Prestige 652 Series User’s Guide
11-12 Firewalls
3. Never give out a password or any sensitive information to an unsolicited telephone call or e-mail.
4. Never e-mail sensitive information such as passwords, credit card information, etc., without encrypting
the information first.
5. 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.
6. 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.
7. 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 #.
8. 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.
9. If you use “chat rooms” or IRC sessions, be careful with any information you reveal to strangers.
10. 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.
11. 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.
11.7 Packet Filtering Vs Firewall
Below are some comparisons between the Prestige’s filtering and firewall functions.
11.7.1 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.
When To Use Filtering
1. To block/allow LAN packets by their MAC addresses.
2. To block/allow special IP packets which are neither TCP nor UDP, nor ICMP packets.