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Linux Security: IPTables

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#1 defurman


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Posted 03 October 2013 - 01:55 PM

Would really like to become proficient at using Iptables but all the tutorials i've seen assume some previous knowledge. All i want is to know how to set a rule, what ports are necessary for surfing the Internet, what ports that should be left open and how to block un desirable websites/users.

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#2 Zen Seeker

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Posted 03 October 2013 - 09:00 PM

If you don't already know what ports are for what you really need to start there. For the most part 80 and 443 is fine for internet traffic but email, ftp, ssh, gmail, DHCP, and many other things will probably need to be left open depending on your setup and needs.


A simple but good iptables guide is here; http://doc.norang.ca/iptables.html


You would be advised to install the linux firewall app "ufw" (Uncomplicated firewall). It also has a GUI but you might find it a little  work to set up, look here; http://gufw.org/


I don't recall the path in Linux and I'm in Windows right now but under Windoes look here; C:\Windows\System32\drivers\etc\services

Make a copy to your desktop and open the copy with notepad. Inside is a very good list to start with.


Example; services file


# Copyright © 1993-2004 Microsoft Corp.
# This file contains port numbers for well-known services defined by IANA
# Format:
# <service name>  <port number>/<protocol>  [aliases...]   [#<comment>]

echo                7/tcp
echo                7/udp
discard             9/tcp    sink null
discard             9/udp    sink null
systat             11/tcp    users                  #Active users
systat             11/udp    users                  #Active users
daytime            13/tcp
daytime            13/udp
qotd               17/tcp    quote                  #Quote of the day
qotd               17/udp    quote                  #Quote of the day
chargen            19/tcp    ttytst source          #Character generator
chargen            19/udp    ttytst source          #Character generator
ftp-data           20/tcp                           #FTP, data
ftp                21/tcp                           #FTP. control
ssh                22/tcp                           #SSH Remote Login Protocol
telnet             23/tcp
smtp               25/tcp    mail                   #Simple Mail Transfer Protocol
time               37/tcp    timserver
time               37/udp    timserver
rlp                39/udp    resource               #Resource Location Protocol
nameserver         42/tcp    name                   #Host Name Server
nameserver         42/udp    name                   #Host Name Server
nicname            43/tcp    whois
domain             53/tcp                           #Domain Name Server
domain             53/udp                           #Domain Name Server
bootps             67/udp    dhcps                  #Bootstrap Protocol Server
bootpc             68/udp    dhcpc                  #Bootstrap Protocol Client
tftp               69/udp                           #Trivial File Transfer
gopher             70/tcp
finger             79/tcp
http               80/tcp    www www-http           #World Wide Web
hosts2-ns          81/tcp                           #HOSTS2 Name Server
hosts2-ns          81/udp                           #HOSTS2 Name Server
kerberos           88/tcp    krb5 kerberos-sec      #Kerberos
kerberos           88/udp    krb5 kerberos-sec      #Kerberos
hostname          101/tcp    hostnames              #NIC Host Name Server
iso-tsap          102/tcp                           #ISO-TSAP Class 0
rtelnet           107/tcp                           #Remote Telnet Service
pop2              109/tcp    postoffice             #Post Office Protocol - Version 2
pop3              110/tcp                           #Post Office Protocol - Version 3
sunrpc            111/tcp    rpcbind portmap        #SUN Remote Procedure Call
sunrpc            111/udp    rpcbind portmap        #SUN Remote Procedure Call
auth              113/tcp    ident tap              #Identification Protocol
uucp-path         117/tcp
sqlserv           118/tcp                           #SQL Services
nntp              119/tcp    usenet                 #Network News Transfer Protocol
ntp               123/udp                           #Network Time Protocol
epmap             135/tcp    loc-srv                #DCE endpoint resolution
epmap             135/udp    loc-srv                #DCE endpoint resolution
netbios-ns        137/tcp    nbname                 #NETBIOS Name Service
netbios-ns        137/udp    nbname                 #NETBIOS Name Service
netbios-dgm       138/udp    nbdatagram             #NETBIOS Datagram Service
netbios-ssn       139/tcp    nbsession              #NETBIOS Session Service
imap              143/tcp    imap4                  #Internet Message Access Protocol
sql-net           150/tcp
sqlsrv            156/tcp
pcmail-srv        158/tcp                           #PCMail Server
snmp              161/udp                           #SNMP
snmptrap          162/udp    snmp-trap              #SNMP trap
print-srv         170/tcp                           #Network PostScript
bgp               179/tcp                           #Border Gateway Protocol
irc               194/tcp                           #Internet Relay Chat Protocol        
ipx               213/udp                           #IPX over IP
rtsps             322/tcp
rtsps             322/udp
mftp              349/tcp
mftp              349/udp
ldap              389/tcp                           #Lightweight Directory Access Protocol
https             443/tcp    MCom                   #HTTP over TLS/SSL
https             443/udp    MCom                   #HTTP over TLS/SSL
microsoft-ds      445/tcp
microsoft-ds      445/udp
kpasswd           464/tcp                           # Kerberos (v5)
kpasswd           464/udp                           # Kerberos (v5)

#3 cryptodan


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Posted 03 October 2013 - 09:09 PM

Here is a complete always up to date version of the /etc/services file located on Linux, and the above pathway for Windows.


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