The Internet is too big and complicated to monitor activities and since it's mostly an open public ground, organizations and individuals are responsible for their security issues. The question is; are we safe behind anti-virus software? Do we consider what goes on when those LED's on our ADSL modems blink? Or how many of us really check security or system logs on Windows or network devices? I guess not many people do that.
But we do not acknowledge the Internet as something complex and tough. So maybe we can continue assuming it's as easy as it was and keep ourselves secure at the same time. There's a simple way to do that, called "packet filtering" which comes by with most of the network devices having a WAN interface, including ADSL modems. It basically stops all inbound traffic from the Internet unless you allow it specifically, or open a 'path' by sending data via a specific port which is blocked for inbound by default. Take port 80 for example, nobody from google.com can connect to your computer by default, but when you open your browser and point it to http://www.google.com you simply begin a two-way traffic, and this allows inbound data to your PC.
It's a simple and effective way to protect many PCs connected to the Internet. Such that you'll know what can not get into your PC.
On the other hand you can even monitor all of the traffic, inbound and outbound, any protocol and any port connection using an expensive but effective solution called "ISA Server" . You can even block any program or traffic that can be potentially used by a program with it. But this solution mostly is for organizations that have to maintain security for many PCs.
As the conclusion, security is an important topic, and there are many web pages that can give you detailed information on what to use and how to use to maintain secure connections. You can check manufacturers' pages, like Microsoft, Cisco, US Robotics, LinkSys etc. You can also check my web page http://techpilgrim.awardspace.com for a brief entry on that topic.
Until next time, stay secure.