Hosts file updater.

#!/bin/bash
# Filename: hosts-update ## file name changed, see "(bug #38022)"
# Version: 030711
# Author: robz
# The hosts file, simple text file that associates IP addresses with hostnames,
# http://en.wikipedia.org/wiki/Hosts_%28file%29 also some more reading and the
# zipped source file http://winhelp2002.mvps.org/hosts.htm
# The script will backup Ubuntu's original hosts file, it must be the original
# to not a modded one, this is insurance so if it all goes pear shaped you'll
# have a clean file escape route, just use as a template and copy it over.
# This script needs to run as root, or automate by dropping it in cron weekly
# and doing "sudo chmod 755 /etc/cron.weekly/hosts-update" in a terminal.
# In case you where wondering, apparently with "127.0.0.1" your browser will
# wait for a timeout hence the editing to "0.0.0.0" which will go straight to
# "404 not found" without waiting.

# EXCLUDES list for any sites you really want but are listed so won't load.
# To exclude a range just list the common part of the pattern, i.e. "666.com"
# will affect many of the addresses whereas "xs.666.co.ruok" is more exclusive,
# case matters by the way Google/google.
EXCLUDES="
troganviriidownload.doh
www.skankyhookers.ick
malwaredrivebyselfservice.eek
deaddodgysoftwarez.duh
google-analytics
googleadservices
adservices.google
adsenseshare.com
"                                                       # Don't block these.
URLHOSTS="http://winhelp2002.mvps.org/hosts.zip"        # Hosts download site.
BAKHOSTS="/etc/hosts.bak"                               # Insurance file.
INMAILTO="robz1@$HOSTNAME root@$HOSTNAME"               # Error/or not mail.

if [ ! -e "$BAKHOSTS" ]; then
    cp /etc/hosts "$BAKHOSTS"                           # Backup original file.
    chmod 444 "$BAKHOSTS"                               # Make it read only.
fi

cd /tmp

# Wget the new hosts file.
if [ ! -e "hosts.zip" ]; then wget -q -i -T 60 "$URLHOSTS"; fi
if [ -e "hosts.zip" ]; then
    echo -e "New hosts file installed, be aware:-\
    \nThis may affect web access to some previously ok websites." | \
    mail -s "[HOSTS FILE] Good download." $INMAILTO
    zenity --notification --text "New Hosts file - Check web access" & disown
else echo -e "Non critical: The weekly download of hosts.zip has failed.\
    \nRun hosts-update.sh as root to install the latest hosts file." | \
    mail -s "[HOSTS FILE] Failed download." $INMAILTO
    exit 1
fi

unzip -c "$(basename "$URLHOSTS")" HOSTS Hosts hosts 2>/dev/null > RAWHOSTS
sed -i 's/.$//' RAWHOSTS                                # Convert dos to unix.

# Create hybrid hosts file.
cat > /tmp/hosts << EOF
#-----------------------------------------------------------------------------
# This hosts block list was created on $(date)
# using the script "hosts-update" by robz.
# It combines the original Ubuntu hosts file saved as "$BAKHOSTS"
# and the latest the hosts file from: $URLHOSTS
#-----------------------------------------------------------------------------

# Start of default hostfile list text copied from "$BAKHOSTS"

$(cat $BAKHOSTS)

# End of default hostfile list text, what follows is supplemental.
#
# Any failure to connect to a previously ok website may be traced to an entry
# in the following list. Modifications to the list should be double hash ##
# commented out rather than deleted.
#
$(sed 's/127.0.0.1/0.0.0.0/g' RAWHOSTS | \
sed -ne '1,/of lines/!p' -e '1,/of entries/!p')

EOF

# Implement excludes list to comment out addresses you don't want to block.
for MODHOSTS in $EXCLUDES; do
sed -i '/'$MODHOSTS'/ s/^\([^## ]\)/## \1/g' hosts
done
mv -f hosts /etc/hosts                                   # Overwrite old hosts.