एक सुरक्षादीवार आपके संगणक और जालक्रम के बीच में स्थित होती हैं, और निश्चित करती हैं कि कौन संसाधन, जालक्रम पर, आपके संगणक सुदूर उपयोगकर्ताओं पर अभिगम के लिए समर्थ हैं। एक उचित विन्यासित सुरक्षादीवार, आपके तंञ की आउट-ऑफ-द-बाँक्स सुरक्षा बहुत अधिक बढ़ा सकता हैं।
आपके तंञ के लिए उचित सुरक्षा लेबल चुनें।
No Firewall — No firewall provides complete access to your system and does no security checking. Security checking is the disabling of access to certain services. This should only be selected if you are running on a trusted network (not the Internet) or plan to do more firewall configuration later.
Enable firewall — If you choose Enable firewall, connections are not accepted by your system (other than the default settings) that are not explicitly defined by you. By default, only connections in response to outbound requests, such as DNS replies or DHCP requests, are allowed. If access to services running on this machine is needed, you can choose to allow specific services through the firewall.
If you are connecting your system to the Internet, but do not plan to run a server, this is the safest choice.
Next, select which services, if any, should be allowed to pass through the firewall.
Enabling these options allow the specified services to pass through the firewall. Note, these services may not be installed on the system by default. Make sure you choose to enable any options that you may need.
WWW (HTTP) — The HTTP protocol is used by Apache (and by other Web servers) to serve webpages. If you plan on making your Web server publicly available, enable this option. This option is not required for viewing pages locally or for developing webpages. You must install the httpd package if you want to serve webpages.
Enabling WWW (HTTP) does not open a port for HTTPS. To enable HTTPS, specify it in the Other ports field.
FTP — The FTP protocol is used to transfer files between machines on a network. If you plan on making your FTP server publicly available, enable this option. You must install the vsftpd package for this option to be useful.
SSH — Secure SHell (SSH) is a suite of tools for logging into and executing commands on a remote machine. If you plan to use SSH tools to access your machine through a firewall, enable this option. You need to have the openssh-server package installed in order to access your machine remotely, using SSH tools.
Telnet — Telnet is a protocol for logging into remote machines. Telnet communications are unencrypted and provide no security from network snooping. Allowing incoming Telnet access is not recommended. If you do want to allow inbound Telnet access, you must install the telnet-server package.
डाक(SMTP) -यह आगमन SMTP डाक वितरण की अनुमति देता हैं। यदि आपको वितरण डाक को सीधे ही आपकी मशीन से जोडने के लिए सुदूर प्रधानों की अनुमति आवश्यक हैं यह विकल्प समर्थ करें।इसे समर्थ नहीं करें यदि आपकी डाक, आप POP3 या IMAP द्वारा आपके ISP's परिसेवक से संग्रह करें या यदि आप fetchmailजैसा एक उपकरण प्रयोग करें। नोट करें कि एक अनुचित विन्यासित SMTP परिसेवक, सुदूर मशीन को लागू करता हैं, आपके परिसेवक के उपयोग के लिए स्पेम भेजने में।
You can allow access to ports which are not listed here, by listing them in the Other ports field. Use the following format: port:protocol. For example, if you want to allow IMAP access through your firewall, you can specify imap:tcp. You can also explicitly specify numeric ports; to allow UDP packets on port 1234 through the firewall, enter 1234:udp. To specify multiple ports, separate them with commas.
Finally, select any devices which should allow access to your system for all traffic from that device.
Selecting any of these trusted devices excludes them from the firewall rules. For example, if you are running a local network, but are connected to the Internet via a PPP dialup, you can check eth0 and any traffic coming from your local network is allowed. Selecting eth0 as trusted means all traffic over the Ethernet is allowed, but the ppp0 interface is still firewalled. If you want to restrict traffic on an interface, leave it unchecked.
It is not recommended that you make any device that is connected to public networks, such as the Internet, a trusted device.