I just got a warning from Linode that the MongoDB instance on Fix This Code was world-usable.

To fix this in sixty seconds or less, use the “ufw” firewall package.

> sudo aptitude install ufw
The following NEW packages will be installed:
  ufw 
0 packages upgraded, 1 newly installed, 0 to remove and 0 not upgraded.
Need to get 143kB of archives. After unpacking 823kB will be used.
Get:1 http://us.archive.ubuntu.com/ubuntu/ maverick/main ufw all 0.30.0-1ubuntu2 [143kB]
Fetched 143kB in 0s (148kB/s)
Preconfiguring packages ...
Selecting previously deselected package ufw.
(Reading database ... 38857 files and directories currently installed.)
Unpacking ufw (from .../ufw_0.30.0-1ubuntu2_all.deb) ...
Processing triggers for man-db ...
Processing triggers for ureadahead ...
Setting up ufw (0.30.0-1ubuntu2) ...

Creating config file /etc/ufw/before.rules with new version

Creating config file /etc/ufw/before6.rules with new version

Creating config file /etc/ufw/after.rules with new version

Creating config file /etc/ufw/after6.rules with new version
Processing triggers for python-central ...

> sudo ufw allow ssh
Rules updated

> sudo ufw allow http
Rules updated

> sudo ufw enable
Command may disrupt existing ssh connections. Proceed with operation (y|n)? y
Firewall is active and enabled on system startup