Millions of personal computers now connect to the Internet through various means. These can include standard modems, ISDN or DSL connections, or broadband cable modems. Telecommunication costs are often low enough that users can stay connected to the Internet for hours. For cable modem, ISDN and DSL users the connection is always on -- allowing the personal computer to act as a server or to perform time-intensive tasks when the user is away. Standard modems require use of a telephone session, but second phone lines with local calling plans are inexpensive enough that many modem users have dedicated lines for their use - again allowing for very long connections.
The problem is that any computer with a live Internet connection is potentially vulnerable to outside attack. The TCP/IP networking software in the computer may allow network ports to be open or available. A hacker with the right software can scan entire subnets of Penn State (including the modem pools) looking for open ports. If one is found it can be exploited by the hacker for their purposes. (One source reports that the entire University is scanned from outside a number of times each day.)
According to D. Ian Hopper, "computer hackers, once satisfied to test their skills on large companies, are turning their sights on home computers that are faster [and] more powerful...The hackers can steal your identity, destroy your data or use your computer to launch attacks on Web sites or your friends." ("Hackers Turn to Home Computers," D. Ian Hopper, AP Technology Writer, 1/3/02).
The obvious risks include potential destruction or copying of important data files and/or programs. Credit card numbers, financial information, and system and network passwords are only a few of the items of private information that can be stolen when a hacker gains access to your computer.
An even more insidious threat comes from hackers who would use your computer as a launching platform for cyber attacks. In February of 2000, a number of large Web sites including CNN, E*Trade, and ZDNet became the victims of denial-of-service (DOS) attacks. A DOS attack happens when a site is flooded by fake outside service requests. The flood of requests overwhelm the service -- effectively preventing legitimate users from access.
In this particular attack, the hackers involved took time to plant software on dozens of computers to which they had gained illicit entry. Most of these computers were in academia, but that is merely a convenience issue. Academic network security, once among the worst in the world, is now beginning to tighten up. Now home systems are at the forefront of vulnerability. Given the current war on terrorism, and the need for increased homeland security, this becomes a very important issue.
Luckily, there is help available. A firewall is a program (or sometimes a piece of hardware) that acts as a network filter. Firewalls can detect and either stop or permit incoming and outgoing network communications. They come in many sizes, from large expensive firewalls intended to protect entire company networks to small personal firewalls for home use. Many firewalls can be configured to block only specific kinds of traffic, or traffic from certain domains. Many firewalls can also tell you when a program on your computer wants to communicate through the network without your awareness.
It is absolutely essential that users of high-speed connections, such as cable modems, ISDN or DSL lines install a firewall. The always-on nature of these connections, and the temptation to allow the computer to act as a server when unattended, make them prime targets for attack. The author also recommends that modem users install a personal firewall. You will be surprised to find that even modem connections are scanned from outside. You will also be surprised when you see how often your current software tries to connect to the outside world. (Often this is OK, but you would want to know.)
There are many firewalls available. The author's favorite, Zone Alarm Personal, is available free for download from http://www.tucows.com. It is a simple firewall that is easy to install and configure. One tip however - after you first install a firewall you may have to grant permissions for many of your current applications to communicate. This can be done on an as-needed basis, and many firewalls will remember your choice so you only have to do it once for a given application.
The bottom line is to protect yourself. Installing a firewall can allow you to sleep easily at night, even if your computer is still doing work on the Internet.