This is a firewall that uses IPTables.
You don't need to know iptables to use it...
Put the following into a text file.
Edit the "definitions" section to match your system.
Make it executable. Execute it.
(There are more complex version if you have a specific issue - but basically this won't let anything through wot you don't ask for.)
# mdh firewall
# Jon "maddog" Hall
# Load appropriate modules.
# remove existing rules
iptables -t nat --flush
MYNET=192.168.23.0/24 # likely IPs for your LAN
LANFACE=eth0 # whatever network device you use for LAN (if any)
WEBFACE=ppp0 # will be whatever network device connects to the internet
# WEBIP= # gateway IP, used for a dual-homed host
### Rules ###
# Set up a default DROP policy for the built-in chains.
iptables -P INPUT DROP
iptables -P FORWARD DROP
iptables -P OUTPUT DROP
# Allow unlimited traffic on the loopback interface.
iptables -A INPUT -i lo -j ACCEPT
iptables -A OUTPUT -o lo -j ACCEPT
# Allow only initiated traffic in
iptables -A INPUT -m state --state RELATED,EXISTING -j ACCEPT
# Allow SSH connections
iptables -A INPUT -t tcp -j ACCEPT -dport 22
# Allow IP Forwarding and use NAT for outgoing connections.
# (Only use for dual homed host acting as an internet gateway.)
# iptables -P FORWARD ACCEPT
# iptables -A POSTROUTING -t NAT -o $WEBFACE -j SNAT --to $WEBIP
# Allow network traffic through ethernet
iptables -A INPUT -i $LANFACE -s $MYNET -j ACCEPT
# Allow all traffic out
# Any other output rule should go /before/ this one
iptables -A OUTPUT -m state --state NEW,RELATED,EXISTING -j ACCEPT
The file manager in DSL is the text based fluxbox. There are graphical file managers available through DSL's tools. Take your pick.