We'll warn you up front that this isn't an article: it's a
presentation converted to HTML over 35 pages. That said, if you're
curious about security issues businesses face, this is an
interesting overview that covers network sniffing (with screenshots
of ethereal in action against a hypothetical CEO's POP client) and
other internal threats and offers some resources for where to start
looking for open source security tools.
It lingers a little overlong on screenshots of defacements and
offers no particular remedy for them, either, but overall it's
still informative as an overview.
The "license" granted for reuse allows presentation provided the
contents aren't altered in any way.