Firewall-ul sub linux

Cu siguranta ati auzit de el… cu siguranta v-a protejat mai mult sau mai putin, chiar si atunci cand erati pe windows. Singura diferenta la ora actuala intre windows si linux este ca sub windows firewall-ul este inutil fara un program antivirus pe cand sub linux el este indeajuns de bun, cu conditia ca el sa fie bine configurat in ceea ce priveste porturile deschise(las deoparte consumul unui antivirus sub windows, comparatia nu isi are rostul).

Totusi ce este un firewall?
În rețelele de calculatoare, un firewall (cuvânt englez care se citește aproximativ ‘fa-iă-uol și înseamnă zid sau paravan anti-incendiar) este un dispozitiv sau o serie de dispozitive configurate în așa fel încât să filtreze, să cripteze sau să intermedieze traficul între diferite domenii de securitate pe baza unor reguli predefinite. Pentru aprofundare, acest link va sta la dispozitie.
Acum ca stim ce este acela un firewall unii dintre voi ar intreba de ce sub windows ar fi inutil fara un antivirus; raspunsul este ca exista mai multi virusi creati pentru windows decat linux. Nici linuxul nu este imun, asta ca sa elimin acest mit al invincibilitatii linuxului, un port deschis gresit sau program ce are o anumita vulnerabilitate pentru un exploit este o gaura de securitate destul de mare.

Pe ce se bazeaza un firewall de linux? Se bazeaza pe iptables, ca sa dau un raspuns mai simplu. Mai detaliat ar fi cam asa: iptables is a user space application program that allows a system administrator to configure the tables provided by the Linux kernel firewall (implemented as different Netfilter modules) and the chains and rules it stores. Different kernel modules and programs are currently used for different protocols; iptables applies to IPv4, ip6tables to IPv6, arptables to ARP, and ebtables as a special for Ethernet frames. Articolul complet il aveti aici.
Sub orice distributie linux pentru a controla regulile din iptables avem un GUI; eu unul folosesc asa ceva deoarece inca nu sunt la un nivel in care sa folosesc linia de comanda. Nu este o rusine sa folosesti un GUI mai ales daca esti incepator. Pe langa interfata grafica oferita de distributie va pot spune ca mai exista si alte programe de gestiune a liniilor din iptables. Acestea sunt:
1. Guarddog Guarddog is a firewall configuration utility for Linux systems. Guarddog is aimed at two groups of users. Novice to intermediate users who are not experts in TCP/IP networking and security, and those users who don’t want the hastle of dealing with cryptic shell scripts and ipchains/iptables parameters.
2. Firestarter Linux security does not have to be complex, and simplicity does not have to mean sacrificing power. With Firestarter you will have a firewall up and running in minutes.
3. Turtlefirewall Turtle Firewall is a software which allows you to realize a Linux firewall in a simply and fast way. It’s based on Kernel 2.4.x/2.6.x and Iptables. Its way of working is easy to understand: you can define the different firewall elements (zones, hosts, networks) and then set the services you want to enable among the different elements or groups of elements.
4. LutelWall LutelWall (formerly known as Lutel Firewall) is high-level linux firewall configuration tool. It uses human-readable and easy to understand configuration to set up Netfilter in most secure way. Its flexibility allows firewall admins build from very simple, single-homed firewalls, to most complex ones – with multiple subnets, DMZ’s and traffic redirections. It can be used on a dedicated firewall system, a multi-function gateway/router/server or on a standalone system. Configuration method of this firewall is designed to be as simple as possible without loosing Netfilter flexibility and its security features.
5. m0n0wall m0n0wall is a project aimed at creating a complete, embedded firewall software package that, when used together with an embedded PC, provides all the important features of commercial firewall boxes (including ease of use) at a fraction of the price (free software).
6. Firewall Builder 4 Firewall Builder is an easy-to-use GUI for creating and managing firewall rules for multiple platforms including iptables, pf and Cisco routers and Cisco ASA/PIX firewalls.
7. Webmin as putea sa il adaug ca si recomandare datorita functiilor multiple pe langa cea de firewall cu interfata web. Webmin is a web-based interface for system administration for Unix. Using any modern web browser, you can setup user accounts, Apache, DNS, file sharing and much more. Webmin removes the need to manually edit Unix configuration files like /etc/passwd, and lets you manage a system from the console or remotely.
Indiferent de programul ales, nu strica sa si verificati configuratia firewall-ului folosind programe precum Ftester sau chiar sa efectuati scanari online alegand unul dintre aceste link-uri: link1, link2 sau link3.

Ca si recomandare personala privind securitatea as adauga ca unele servicii precum SSH sau FTP pot folosi si alte porturi decat cele standart(daca este necesar ca ele sa fie deschise) si ca nu ar strica sa aveti active alaturi de firewall programe precum portsentry si programe ce verifica dupa anumite rootkit-uri precum rkhunter sau chkrootkit(rkhunter si chkrootkit pot fi disponibile si in repo-urile distributiei linux folosite).

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