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Re: [cobalt-users] Firewall/IPChains Rules - UPDATED



----- Original Message -----
From: "Craig Napier" <craignapier@xxxxxxxxxxx>
To: <cobalt-users@xxxxxxxxxxxxxxx>
Sent: Saturday, March 03, 2001 7:42 AM
Subject: [cobalt-users] Firewall/IPChains Rules - UPDATED


> Update to previously posted firewall script. This one adds support for
> *client* side SMTP, which you may want if forms are to send out replys
> (e.g., thank you messages from submissions).  :-)
>
> Craig
>
>
> #!/bin/sh
>
> # Script generated Fri Mar  2 05:15:12 2001
>
>
> #
> --------------------------------------------------------------------------
--
> # Copyright (C) 1997, 1998, 1999, 2000  Robert L. Ziegler
> #
> #  Permission to use, copy, modify, and distribute this software and its
> #  documentation for educational, research, private and non-profit
purposes,
> #  without fee, and without a written agreement is hereby granted.
> #  This software is provided as an example and basis for individual
firewall
> #  development.  This software is provided without warranty.
> #
> #  Any material furnished by Robert L. Ziegler is furnished on an
> #  "as is" basis.  He makes no warranties of any kind, either expressed
> #  or implied as to any matter including, but not limited to, warranty
> #  of fitness for a particular purpose, exclusivity or results obtained
> #  from use of the material.
> #
> --------------------------------------------------------------------------
--
>
> #  /etc/rc.d/rc.firewall
> #  Invoked from /etc/rc.d/rc.local.
>
> echo "Starting firewalling... "
>
> #
> --------------------------------------------------------------------------
--
> #  Some definitions for easy maintenance.
> #  EDIT THESE TO SUIT YOUR SYSTEM AND ISP.
>
> EXTERNAL_INTERFACE="eth0"               # Internet connected interface
> LOOPBACK_INTERFACE="lo"                 # or your local naming convention
>
> IPADDR="any/0"                          # your IP address
>
> ANYWHERE="any/0"                        # match any IP address
>
> NAMESERVER_1="any/0"                    # everyone must have at least one
>
> SMTP_SERVER="any/0"                     # Your ISP mail gateway. Your
relay.
>
> LOOPBACK="127.0.0.0/8"                  # reserved loopback address range
> CLASS_A="10.0.0.0/8"                    # class A private networks
> CLASS_B="172.16.0.0/12"                 # class B private networks
> CLASS_C="192.168.0.0/16"                # class C private networks
> CLASS_D_MULTICAST="224.0.0.0/4"         # class D multicast addresses
> CLASS_E_RESERVED_NET="240.0.0.0/5"      # class E reserved addresses
> BROADCAST_SRC="0.0.0.0"                 # broadcast source address
> BROADCAST_DEST="255.255.255.255"        # broadcast destination address
> PRIVPORTS="0:1023"                      # well known, privileged port
range
> UNPRIVPORTS="1024:65535"                # unprivileged port range
>
> #
> --------------------------------------------------------------------------
--
>
> NFS_PORT="2049"                         # (TCP/UDP) NFS
> SOCKS_PORT="1080"                       # (TCP) Socks
> OPENWINDOWS_PORT="2000"                 # (TCP) openwindows
>
> # X Windows port allocation begins at 6000 and increments to 6063
> # for each additional server running.
> XWINDOW_PORTS="6000:6063"               # (TCP) X windows
>
> # The SSH client starts at 1023 and works down to 513 for each
> # additional simultaneous connection originating from a privileged port.
> # Clients can optionally be configured to use only unprivileged ports.
> SSH_LOCAL_PORTS="1022:65535"            # port range for local clients
> SSH_REMOTE_PORTS="513:65535"            # port range for remote clients
>
> # traceroute usually uses -S 32769:65535 -D 33434:33523
> TRACEROUTE_SRC_PORTS="32769:65535"
> TRACEROUTE_DEST_PORTS="33434:33523"
>
> #
> --------------------------------------------------------------------------
--
> # Default policy is DENY
> # Explicitly accept desired INCOMING & OUTGOING connections
>
>     # Remove all existing rules belonging to this filter
>     ipchains -F
>
>     # Set the default policy of the filter to deny.
>     ipchains -P input  DENY
>     ipchains -P output REJECT
>     ipchains -P forward DENY
>
> #
> --------------------------------------------------------------------------
--
>
>     # Enable TCP SYN Cookie Protection
>     echo 1 > /proc/sys/net/ipv4/tcp_syncookies
>
>     # Enable always defragging Protection
>     echo 1 > /proc/sys/net/ipv4/ip_always_defrag
>
>     # Enable broadcast echo  Protection
>     echo 1 > /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts
>
>     # Enable bad error message  Protection
>     echo 1 > /proc/sys/net/ipv4/icmp_ignore_bogus_error_responses
>
>     # Enable IP spoofing protection
>     # turn on Source Address Verification
>     for f in /proc/sys/net/ipv4/conf/*/rp_filter; do
>         echo 1 > $f
>     done
>
>     # Disable ICMP Redirect Acceptance
>     for f in /proc/sys/net/ipv4/conf/*/accept_redirects; do
>         echo 0 > $f
>     done
>
>     for f in /proc/sys/net/ipv4/conf/*/send_redirects; do
>         echo 0 > $f
>     done
>
>     # Disable Source Routed Packets
>     for f in /proc/sys/net/ipv4/conf/*/accept_source_route; do
>         echo 0 > $f
>     done
>
>     # Log Spoofed Packets, Source Routed Packets, Redirect Packets
>     for f in /proc/sys/net/ipv4/conf/*/log_martians; do
>         echo 1 > $f
>     done
>
>
> #
> --------------------------------------------------------------------------
--
> # LOOPBACK
>
>     # Unlimited traffic on the loopback interface.
>
>     ipchains -A input  -i $LOOPBACK_INTERFACE  -j ACCEPT
>     ipchains -A output -i $LOOPBACK_INTERFACE  -j ACCEPT
>
> #
> --------------------------------------------------------------------------
--
> # Network Ghouls
>
>     # Deny access to jerks
>     # --------------------
>     # /etc/rc.d/rc.firewall.blocked contains a list of
>     # ipchains -A input -i $EXTERNAL_INTERFACE -s address -j DENY
>     # rules to block from any access.
>
>     # Refuse any connection from problem sites
>     if [ -f /etc/rc.d/rc.firewall.blocked ]; then
>         . /etc/rc.d/rc.firewall.blocked
>     fi
>
> #
> --------------------------------------------------------------------------
--
> # SPOOFING & BAD ADDRESSES
> # Refuse spoofed packets.
> # Ignore blatantly illegal source addresses.
> # Protect yourself from sending to bad addresses.
> #
> #    # Refuse incoming packets pretending to be from the external address.
> #    ipchains -A input   -s $IPADDR -j DENY -l
> #
>     # Refuse incoming packets claiming to be from a Class A, B or C
private
> network
>     ipchains -A input   -s $CLASS_A -j DENY
>     ipchains -A input   -s $CLASS_B -j DENY
>     ipchains -A input   -s $CLASS_C -j DENY
>
>     # Refuse broadcast address SOURCE packets
>     ipchains -A input   -s $BROADCAST_DEST -j DENY
>     ipchains -A input   -d $BROADCAST_SRC -j DENY
>
>     # Refuse Class D multicast addresses
>     # Multicast is illegal as a source address.
>     # Multicast uses UDP.
>     ipchains -A input   -s $CLASS_D_MULTICAST -j DENY
>
>     # Refuse Class E reserved IP  addresses
>     ipchains -A input   -s $CLASS_E_RESERVED_NET -j DENY -l
>
>     # Refuse special addresses defined as reserved by the IANA.
>     # Note:  The remaining reserved addresses are not included.
>     # Filtering them causes problems as reserved blocks are
>     # being allocated more often now.
>
>     # Note:  this list includes the loopback, multicast, & reserved
> addresses.
>
>     # 0.*.*.*           - Can't be blocked for DHCP users.
>     # 127.*.*.*         - LoopBack
>     # 169.254.*.*       - Link Local Networks
>     # 192.0.2.*         - TEST-NET
>     # 224-255.*.*.*     - Classes D & E, plus unallocated.
>
>     ipchains -A input   -s 0.0.0.0/8 -j DENY -l
>     ipchains -A input   -s 127.0.0.0/8 -j DENY -l
>     ipchains -A input   -s 169.254.0.0/16 -j DENY -l
>     ipchains -A input   -s 192.0.2.0/24 -j DENY -l
>     ipchains -A input   -s 224.0.0.0/3 -j DENY -l
>
> #
> --------------------------------------------------------------------------
--
> # NOTE:
> #      The symbolic names used in /etc/services for the port numbers vary
by
> #      supplier.  Using them is less error prone and more meaningful,
> though.
>
> #
> --------------------------------------------------------------------------
--
> # TCP UNPRIVILEGED PORTS
> # Avoid ports subject to protocol & system administration problems.
>
>     # NFS: establishing a TCP connection
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p tcp -y \
>              --destination-port $NFS_PORT -j DENY -l
>     ipchains -A output -i $EXTERNAL_INTERFACE -p tcp -y \
>              --destination-port $NFS_PORT -j REJECT
>
>     # openwindows: establishing a connection
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p tcp -y \
>              --destination-port $OPENWINDOWS_PORT -j DENY -l
>     ipchains -A output -i $EXTERNAL_INTERFACE -p tcp -y \
>              --destination-port $OPENWINDOWS_PORT -j REJECT
>
>
>     # Xwindows: establishing a connection
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p tcp -y \
>              --destination-port $XWINDOW_PORTS -j DENY -l
>     ipchains -A output -i $EXTERNAL_INTERFACE -p tcp -y \
>              --destination-port $XWINDOW_PORTS -j REJECT
>
>     # SOCKS: establishing a connection
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p tcp -y \
>              --destination-port $SOCKS_PORT -j DENY -l
>     ipchains -A output -i $EXTERNAL_INTERFACE -p tcp -y \
>              --destination-port $SOCKS_PORT -j REJECT
>
> #
> --------------------------------------------------------------------------
--
> # UDP UNPRIVILEGED PORTS
> # Avoid ports subject to protocol & system administration problems.
>
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p udp  \
>              --destination-port $NFS_PORT -j DENY -l
>
>     # UDP INCOMING TRACEROUTE
>     # traceroute usually uses -S 32769:65535 -D 33434:33523
>
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p udp  \
>              --source-port $TRACEROUTE_SRC_PORTS \
>              --destination-port $TRACEROUTE_DEST_PORTS -j DENY -l
>
>
>     # DNS server (53)
>     # ---------------
>
>     # DNS: full server
>     # ----------------
>
>     # server/client to server query or response
>
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p udp  \
>              --source-port $UNPRIVPORTS \
>              -d $IPADDR 53 -j ACCEPT
>
>     ipchains -A output -i $EXTERNAL_INTERFACE -p udp  \
>              -s $IPADDR 53 \
>              --destination-port $UNPRIVPORTS -j ACCEPT
>
>     ipchains -A output -i $EXTERNAL_INTERFACE -p udp  \
>              -s $IPADDR 53 \
>              --destination-port 53 -j ACCEPT
>
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p udp  \
>              --source-port 53 \
>              -d $IPADDR 53 -j ACCEPT
>
>
>     # DNS client (53)
>     # ---------------
>     ipchains -A output -i $EXTERNAL_INTERFACE -p udp  \
>              -s $IPADDR $UNPRIVPORTS \
>              -d $NAMESERVER_1 53 -j ACCEPT
>
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p udp  \
>              -s $NAMESERVER_1 53 \
>              -d $IPADDR $UNPRIVPORTS -j ACCEPT
>
>
>     ipchains -A output -i $EXTERNAL_INTERFACE -p tcp  \
>              -s $IPADDR $UNPRIVPORTS \
>              -d $NAMESERVER_1 53 -j ACCEPT
>
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p tcp ! -y \
>              -s $NAMESERVER_1 53 \
>              -d $IPADDR $UNPRIVPORTS -j ACCEPT
>
>     # ------------------------------------------------------------------
>
>     # HTTP server (80)
>     # ----------------
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p tcp  \
>              --source-port $UNPRIVPORTS \
>              -d $IPADDR 80 -j ACCEPT
>
>     ipchains -A output -i $EXTERNAL_INTERFACE -p tcp ! -y \
>              -s $IPADDR 80 \
>              --destination-port $UNPRIVPORTS -j ACCEPT
>
>
>     # HTTP client (80)
>     # ----------------
>     ipchains -A output -i $EXTERNAL_INTERFACE -p tcp  \
>              -s $IPADDR $UNPRIVPORTS \
>              --destination-port 80 -j ACCEPT
>
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p tcp ! -y \
>              --source-port 80 \
>              -d $IPADDR $UNPRIVPORTS -j ACCEPT
>
>
>     # ADMIN server (81)
>     # ----------------
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p tcp  \
>              --source-port $UNPRIVPORTS \
>              -d $IPADDR 81 -j ACCEPT
>
>     ipchains -A output -i $EXTERNAL_INTERFACE -p tcp ! -y \
>              -s $IPADDR 81 \
>              --destination-port $UNPRIVPORTS -j ACCEPT
>
>     # ------------------------------------------------------------------
>
>     # HTTPS server (443)
>     # ------------------
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p tcp  \
>              --source-port $UNPRIVPORTS \
>              -d $IPADDR 443 -j ACCEPT
>
>     ipchains -A output -i $EXTERNAL_INTERFACE -p tcp ! -y \
>              -s $IPADDR 443 \
>              --destination-port $UNPRIVPORTS -j ACCEPT
>
>
>     # HTTPS client (443)
>     # ------------------
>     ipchains -A output -i $EXTERNAL_INTERFACE -p tcp  \
>              -s $IPADDR $UNPRIVPORTS \
>              --destination-port 443 -j ACCEPT
>
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p tcp ! -y \
>              --source-port 443 \
>              -d $IPADDR $UNPRIVPORTS -j ACCEPT
>
>     # ------------------------------------------------------------------
>
>     # POP server (110)
>     # ----------------
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p tcp  \
>              --source-port $UNPRIVPORTS \
>              -d $IPADDR 110 -j ACCEPT
>
>     ipchains -A output -i $EXTERNAL_INTERFACE -p tcp ! -y \
>              -s $IPADDR 110 \
>              --destination-port $UNPRIVPORTS -j ACCEPT
>
>     # ------------------------------------------------------------------
>
>     # SMTP server (25)
>     # ----------------
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p tcp  \
>              --source-port $UNPRIVPORTS \
>              -d $IPADDR 25 -j ACCEPT
>
>     ipchains -A output -i $EXTERNAL_INTERFACE -p tcp ! -y \
>              -s $IPADDR 25 \
>              --destination-port $UNPRIVPORTS -j ACCEPT
>
>
>     # SMTP client (25)
>     # ----------------
>     ipchains -A output -i $EXTERNAL_INTERFACE -p tcp  \
>              -s $IPADDR $UNPRIVPORTS \
>              -d $SMTP_SERVER 25 -j ACCEPT
>
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p tcp ! -y \
>              -s $SMTP_SERVER 25 \
>              -d $IPADDR $UNPRIVPORTS -j ACCEPT
>
>     # ------------------------------------------------------------------
>
>     # SSH server (22)
>     # ---------------
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p tcp  \
>              --source-port $SSH_REMOTE_PORTS \
>              -d $IPADDR 22 -j ACCEPT
>
>     ipchains -A output -i $EXTERNAL_INTERFACE -p tcp ! -y \
>              -s $IPADDR 22 \
>              --destination-port $SSH_REMOTE_PORTS -j ACCEPT
>
>
>     # SSH client (22)
>     # ---------------
>     ipchains -A output -i $EXTERNAL_INTERFACE -p tcp  \
>              -s $IPADDR $SSH_LOCAL_PORTS \
>              --destination-port 22 -j ACCEPT
>
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p tcp ! -y \
>              --source-port 22 \
>              -d $IPADDR $SSH_LOCAL_PORTS -j ACCEPT
>
> #    # ------------------------------------------------------------------
> #
> #    # TELNET server (23)
> #    # ------------------
> #    ipchains -A input  -i $EXTERNAL_INTERFACE -p tcp  \
> #             --source-port $UNPRIVPORTS \
> #             -d $IPADDR 23 -j ACCEPT
> #
> #    ipchains -A output -i $EXTERNAL_INTERFACE -p tcp ! -y \
> #             -s $IPADDR 23 \
> #             --destination-port $UNPRIVPORTS -j ACCEPT
> #
>     # ------------------------------------------------------------------
>
>     # AUTH server (113)
>     # -----------------
>
>     # Accept incoming connections to identd but disable in.identd in
> inetd.conf.
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p tcp  \
>              --source-port $UNPRIVPORTS \
>              -d $IPADDR 113 -j ACCEPT
>
>     ipchains -A output -i $EXTERNAL_INTERFACE -p tcp ! -y \
>              -s $IPADDR 113 \
>              --destination-port $UNPRIVPORTS -j ACCEPT
>
>
>     # AUTH client (113)
>     # -----------------
>     ipchains -A output -i $EXTERNAL_INTERFACE -p tcp  \
>              -s $IPADDR $UNPRIVPORTS \
>              --destination-port 113 -j ACCEPT
>
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p tcp ! -y \
>              --source-port 113 \
>              -d $IPADDR $UNPRIVPORTS -j ACCEPT
>
> #    # ------------------------------------------------------------------
> #
> #    # WHOIS client (43)
> #    # -----------------
> #    ipchains -A output -i $EXTERNAL_INTERFACE -p tcp  \
> #             -s $IPADDR $UNPRIVPORTS \
> #             --destination-port 43 -j ACCEPT
> #
> #    ipchains -A input  -i $EXTERNAL_INTERFACE -p tcp ! -y \
> #             --source-port 43 \
> #             -d $IPADDR $UNPRIVPORTS -j ACCEPT
> #
>     # ------------------------------------------------------------------
>
>     # FTP server (21)
>     # ---------------
>
>     # incoming request
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p tcp  \
>              --source-port $UNPRIVPORTS \
>              -d $IPADDR 21 -j ACCEPT
>
>     ipchains -A output -i $EXTERNAL_INTERFACE -p tcp ! -y \
>              -s $IPADDR 21 \
>              --destination-port $UNPRIVPORTS -j ACCEPT
>
>
>     # PORT MODE data channel responses
>     ipchains -A output -i $EXTERNAL_INTERFACE -p tcp  \
>              -s $IPADDR 20 \
>              --destination-port $UNPRIVPORTS -j ACCEPT
>
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p tcp ! -y \
>              --source-port $UNPRIVPORTS \
>              -d $IPADDR 20 -j ACCEPT
>
>
>     # PASSIVE MODE data channel responses
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p tcp  \
>              --source-port $UNPRIVPORTS \
>              -d $IPADDR $UNPRIVPORTS -j ACCEPT
>
>     ipchains -A output -i $EXTERNAL_INTERFACE -p tcp ! -y \
>              -s $IPADDR $UNPRIVPORTS \
>              --destination-port $UNPRIVPORTS -j ACCEPT
>
>
>     # FTP client (21)
>     # ---------------
>
>     # outgoing request
>     ipchains -A output -i $EXTERNAL_INTERFACE -p tcp  \
>              -s $IPADDR $UNPRIVPORTS \
>              --destination-port 21 -j ACCEPT
>
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p tcp ! -y \
>              --source-port 21 \
>              -d $IPADDR $UNPRIVPORTS -j ACCEPT
>
>
>     # PORT mode data channel
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p tcp  \
>              --source-port 20 \
>              -d $IPADDR $UNPRIVPORTS -j ACCEPT
>
>     ipchains -A output -i $EXTERNAL_INTERFACE -p tcp ! -y \
>              -s $IPADDR $UNPRIVPORTS \
>              --destination-port 20 -j ACCEPT
>
>
>     # PASSIVE mode data channel creation
>     ipchains -A output -i $EXTERNAL_INTERFACE -p tcp  \
>              -s $IPADDR $UNPRIVPORTS \
>              --destination-port $UNPRIVPORTS -j ACCEPT
>
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p tcp ! -y \
>              --source-port $UNPRIVPORTS \
>              -d $IPADDR $UNPRIVPORTS -j ACCEPT
>
> #
> --------------------------------------------------------------------------
--
> # ICMP
>
>     #    To prevent denial of service attacks based on ICMP bombs, filter
>     #    incoming Redirect (5) and outgoing Destination Unreachable (3).
>     #    Note, however, disabling Destination Unreachable (3) is not
>     #    advisable, as it is used to negotiate packet fragment size.
>
>     # For bi-directional ping.
>     #     Message Types:  Echo_Reply (0),  Echo_Request (8)
>     #     To prevent attacks, limit the src addresses to your ISP range.
>     #
>     # For outgoing traceroute.
>     #     Message Types:  INCOMING Dest_Unreachable (3), Time_Exceeded
(11)
>     #     default UDP base: 33434 to base+nhops-1
>     #
>     # For incoming traceroute.
>     #     Message Types:  OUTGOING Dest_Unreachable (3), Time_Exceeded
(11)
>     #     To block this, deny OUTGOING 3 and 11
>
>     #  0: echo-reply (pong)
>     #  3: destination-unreachable, port-unreachable, fragmentation-needed,
> etc.
>     #  4: source-quench
>     #  5: redirect
>     #  8: echo-request (ping)
>     # 11: time-exceeded
>     # 12: parameter-problem
>
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p icmp  \
>              --icmp-type echo-reply \
>              -d $IPADDR -j ACCEPT
>
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p icmp  \
>              --icmp-type destination-unreachable \
>              -d $IPADDR -j ACCEPT
>
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p icmp  \
>              --icmp-type source-quench \
>              -d $IPADDR -j ACCEPT
>
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p icmp  \
>              --icmp-type time-exceeded \
>              -d $IPADDR -j ACCEPT
>
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p icmp  \
>              --icmp-type parameter-problem \
>              -d $IPADDR -j ACCEPT
>
>
>     ipchains -A output -i $EXTERNAL_INTERFACE -p icmp  \
>              -s $IPADDR fragmentation-needed -j ACCEPT
>
>     ipchains -A output -i $EXTERNAL_INTERFACE -p icmp  \
>              -s $IPADDR source-quench -j ACCEPT
>
>     ipchains -A output -i $EXTERNAL_INTERFACE -p icmp  \
>              -s $IPADDR echo-request -j ACCEPT
>
>     ipchains -A output -i $EXTERNAL_INTERFACE -p icmp  \
>              -s $IPADDR parameter-problem -j ACCEPT
>
> #
> --------------------------------------------------------------------------
--
> # Enable logging for selected denied packets
>
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p tcp  \
>              --destination-port 0:19 -j DENY -l
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p tcp  \
>              --destination-port 24 -j DENY -l
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p tcp  \
>              --destination-port 26:78 -j DENY -l
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p tcp  \
>              --destination-port 81:109 -j DENY -l
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p tcp  \
>              --destination-port 112 -j DENY -l
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p tcp  \
>              --destination-port 114:136 -j DENY -l
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p tcp  \
>              --destination-port 140:142 -j DENY -l
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p tcp  \
>              --destination-port 144:442 -j DENY -l
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p tcp  \
>              --destination-port 444:1023 -j DENY -l
>
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p udp  \
>              --destination-port 0:110 -j DENY -l
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p udp  \
>              --destination-port 112:160 -j DENY -l
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p udp  \
>              --destination-port 163:634 -j DENY -l
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p udp  \
>              --destination-port 636:1023 -j DENY -l
>
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p udp  \
>              --destination-port $UNPRIVPORTS -j DENY -l
>
>
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p icmp  \
>              --icmp-type 5 -j DENY -l
>     ipchains -A input  -i $EXTERNAL_INTERFACE -p icmp  \
>              --icmp-type 13:255 -j DENY -l
>
>     ipchains -A output -i $EXTERNAL_INTERFACE  -j REJECT
>
> #
> --------------------------------------------------------------------------
--
>
> echo "done"
>
> exit 0
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