What is computer security?

Unauthorised people who try to break into computers, either in a local network or using the Internet are called intruders. They may not care about your identity. Often they want to gain control of your computer so they can use it to launch attacks on other computer systems. Having control of your computer gives them the ability to hide their true location as they launch attacks, often against high-profile computer systems such as government or financial systems. Even if you have a computer connected to the Internet only to play the latest games or to send email to friends and family, your computer may be a target.

Unfortunately, intruders are always discovering new vulnerabilities (informally called "holes") to exploit in computer software. The complexity of software makes it increasingly difficult to fully test. When holes are discovered, computer vendors will make patches to fix them. However, it is up to the user to find and install the patches. Most of the incident reports of computer break-ins received at CERTCC and AusCERT could have been prevented if system administrators and users kept patches up-to-date.

Trojan Horse

Back Door and Remote Administration Programs

On Windows systems, two tools commonly used by intruders are BackOrifice and Netbus. These are known as back door or remote administration programs; once installed, they allow other people to access and control your computer. We recommend that you review the CERT vulnerability note about Back Orifice. This document describes how it works, how to detect it, and how to protect your systems from it:

Denial of Service

Another form of attack is called a Denial of Service (DoS) attack. This type of attack causes your computer to crash or to become so overloaded that you are unable to use it. In most cases, the latest patches will prevent the attack. The following document describes Denial of Service attacks in greater detail.

What can I do to better secure a computer running Windows 95/98?

Prevention

The best way to secure your computer is to prevent intruders from attacking your system in the first place. To do this, install current patches for your operating system and your applications. Beyond patches, be aware of the types of attacks and vulnerabilities used by intruders, install only the applications you really need, and back up your data regularly.

As there is an increase in digital subscriber line (xDSL) and cable modems more home computers are constantly connected to the Internet. Consider setting up a firewall to prevent intruders from breaking into your computer. A simple firewall for home use could be put together using an old 486 computer (very cheap) running Linux (free). The following document discusses how to setup a firewall with Linux.

Virus Protection

Computer viruses are another wide spread problem. They spread easily through floppy disks, email, or by programs downloaded from the Internet. They can cause problems ranging from reformatting your hard drive to changing data. Once created, viruses spread without help from their creators. You can get them from people at the office, using computers at school, or in a document emailed to you by a friend.

To protect yourself, we recommend that you install a virus scanning/detecting/cleaning program. The following Computer Virus Resources document has a number of links to information about computer viruses, hoaxes, and chain letters.

Where can I get updates and patches?

Windows 95

Windows 98

• Use the Microsoft Windows Update, which is part of the Start menu.

Microsoft Office

Internet Explorer

Netscape

• If you are using Navigator 4.02 or higher, you can use the SmartUpdate. Go to the Help menu and then select Software Updates.
• Also review the information about security available under the Help menu.

Other sources for updates and patches

• Most product documentation offers a method to get updates and patches. You should be able to obtain updates from the vendor's Web site. Read the manuals or browse the vendor's Web site for more information.

How do I find out if there is a new patch for an application?

Some vendors offer a mailing list service that automatically sends you mail when updates become available. Look on your vendor's Web site for information about automatic notification. If no mailing list is offered you may need to check periodically for updates.

If you have data on your system that you would like to keep more secure than Windows 95/98 allows, choose another operating system that offers better security. Consider using Microsoft Windows NT or a version of Unix.

What security concerns are there with...

MS Office?

Web browsers store pieces of information called "cookies" on your computer. Although these are meant to be a useful tool, they can also be used to gather information about your browsing habits, favorite sites, etc. It is possible to change the settings to notify you of the cookies being written to your computer or to completely disable cookies. The following CIAC Information Bulletin has further information on Internet cookies.

There are various security issues to be aware of when you use email. First, messages you send pass through many computers across the Internet. Any one of these systems could have someone reading the mail that passes through it. To prevent strangers from reading your email, the best method is to encrypt your messages. The most popular method to encrypt email is to use a program called Pretty Good Privacy (PGP) or Gnu Privacy Guard (GnuPG). These programs offer many options for encrypting files. Some email programs also offer easy methods for encrypting and unencrypting messages within the application. For further information about GnuPG and PGP, visit the following web sites.

Wingate?

Wingate is a popular package that allows a number of computers on a LAN to share a single Internet address. Wingate could be configured to allow an intruder to use a Wingate server to conceal their true location. Further information can be found in the following vulnerability note.

Where else can I get information about computer security?

In what locations should I be concerned about computer security?

• Office -- Do you know the computer security policy at your office?
• School -- Are these systems scanned for possible computer viruses?
• Friends and Family -- Do you know what software others are installing on your computer?