Fujitsu AP-600RP-USB manual Firewall, Increased firewall protection by closing the ports

CONNECT2AIR™ WLAN AP-600RP-USB Page 46 / 62

8.5.2 Firewall

The firewall is a set of programs located at the gateway, which limits the exposure of a computer or a group of computers to users in the WAN network or Internet. Based on the default policies and the specified rules, network administrators can easily manage the traf- fic from any network access. The default policies allow you to accept or block all traffic. You can also define rules: these determine what to do with specific types of traffic where rules override the default policies.

The firewall offers extended protection against DoS (denial of service) attacks. Clients connected to the Internet are exposed to attacks of this nature. Here, a third party attempts to render the client or the host network inaccessible by bombarding the client with count- less IP packets until the client's resources become exhausted. With DDOS (distributed denial of service), the attacks come in groups, which increases the extent of the damage.

The router is also equipped with NAT (Network Address Translation) to protect the local network by means of a special mechanism: clients are non-transparent to the Internet. This means that a local PC with the IP address 192.168.1.101 is not visible as the source of a message through its address. The message is "masked" by NAT and the WAN IP ad- dress of the router (i.e., AccessPoint) appears as the source. The AccessPoint itself saves the data regarding the true identity of a message and can forward a reply from the Internet to the proper source if necessary.

Increased firewall protection by closing the ports

The security level of a firewall can be increased by successively closing one port after an- other since hackers as well as viruses always look for opportunities to penetrate the fire- wall through open ports. It is therefore also useful to close any ports that are not absolutely necessary.

This method of increasing security is available to users who are familiar with the

resources of the applications used. Remote administration programs, for example, in some cases use ports that have been reserved specially for the application. Please obtain details from the vendors regarding the software used.

Service	Function	TCP	UDP
AUTH	Authentication Service	113	113
BOOTPC	Bootstrap Protocol Client		67
DNS	Domain Name Server		53
FTP	File Transfer Protocol	21
HTTP	Hyper Text Transfer Protocol	80
NETBIOS-SSN	Netbios Session Service	139
NNTP	Network News Transfer Protocol	119
NPP	Network Printing Protocol	92
NTP	Network Time Protokol	123
POP3	Post Office Protocol V3	110
PPTP	Point to Point Tunneling Protocol (VPN)	1723
SMTP	Simple Mail Transfer Protocol	25
SNMP	Simple Network Management Protocol		161
Telnet	Terminal Emulation Protocol	23
TFTP	Trivial File Transfer Protocol		69

Different applications are available on the Internet for checking the firewall from the Inter- net. Also make inquiries at anti-virus SW vendors regarding ports that are attacked by vi- ruses and take appropriate measures.