Security on the Internet / Intrusion into your system

Resource sharing

Most operating systems will allow resource sharing on network connected computers. Although this characteristic is very useful on a local network, it can open the gate to your system when connected to the Internet. By activating the disk sharing function, you allow every one on the Internet to access your personal or business files and expose your computer to complete deletion of its data and programs.

To grant to others unrestricted access to your computer proves particularly risky. If, for some reason, you must absolutely do so, please ensure it is done applying appropriate safety measures:

• Protect access to your resources with a password difficult to decipher.
• Do not leave the sharing function permanently activated, and deactivate without delay.
• Limit the authorization granted to bare essential.

For example, if you want to share your printer with a co-worker, do not grant this permission to the whole world. You may soon run out of paper ! Granting access to your hard disk may prove even more treacherous. When you are connected to the Internet, you should always grant it in read only and in a well circumscribed sub-directory.

In this respect, pay particular attention to your operating system's messages. Windows Browser and Finder under MacOS version 8 or a later version, for example, will display icons, from time to time, announcing that the resource sharing function is activated in your systemÊ:

		Disk sharing under Windows
		Folder sharing under Windows
		Folder sharing under Macintosh (Mac OS 8 or a later version)

Trojan horse 

The Trojan Horse is often utilized for unlawful intrusion into an information processing system. Because of the importance of this threat and its noted frequency, we devoted an entire page to the subject and strongly suggest you become familiar with it.

Web servers and other services

Certain software install an HTTP server on your computer to display Web pages. In particular, it is the case of a few Web page editors such as Microsoft Front Page. Apart from the fact that it is specifically prohibited to circulate data from any type of server onto the Internet network in Vidéotron's service contract governing the use of your internet access, the installation of such servers in your system often opens doors to intruders. It is the case, in particular, of many CGI programs installed implicitly on Web servers or later developed by programmers.

Rather than expose yourself to intrusions and their unsuspected consequences, use the space provided for your personal Web page on the Canoë server (included with your Vidéotron Internet access, except for Découverte subscribers).

There are other types of servers and services that provide an entry into your system. Unless you are familiar with configuration, download of the latest updates, keeping regularly informed of the latest security breaches which are discovered periodically, the installation of Proxy servers, FTP (particularly FTP anonymous), SMTP, Sendmail and remote servers (rsh, rlogin, etc.) and others, those services are likely to create significant breaches of security. Do not use such services.

Remote control software

Certain pcAnywhere-type software give the possibility to carry out debugging services by granting the person remote control of a distant computer. Through this link, the keyboard, the mouse and the screen of the person who takes control become an extension, so to speak, of those of the distant computer. This type of software is often used by mobile users to access files they cannot carry or to connect to the office network from a distance.

Although this software makes it possible to carry out a completely legitimate remote control, if it were so agreed between two users, it goes without saying that this type of access must absolutely be protected by a username and a password difficult to decipher. Any failure to this basic security measure would be an open invitation to hackers, who will not miss taking advantage of the breach. Indeed, communication ports used by software of this type are frequently probed by hackers in search of unauthorized means of access.

Another problem frequently encountered with this software comes from incomplete configuration. When you do not specify the IP address of the computer to be reached at the time of an attempt at remote control, certain software send their request to all computers of a same sub-network (class C), therefore sweeping a whole class of addresses. It is the case, in particular, of at least one version of pcAnywhere. Cyber surfers who have protected their access with specialized tools will record such an operation as an illicit attempt at intrusion on your part, which could lead to complaints. With this type of software, it is therefore important to specify, in the configuration, the IP address of the user with whom you have agreed on such an operation before activating the remote control function.

Specialized tools

Specialized tools such as firewalls make it possible to protect your computer from intrusions. It is advisable, however, to note that a hasty installation or an incomplete configuration of the software could create breaches. If you must absolutely open certain accesses to your system, it is recommended that you familiarize with the implied concepts and read the documentation provided by manufacturers. A few resources are suggested below:

Windows
	Shields UP! ConSeal ® PC FIREWALL Norton Internet Security
Macintosh
	NetBarrier The DoorStop Firewall
Unix
	Tripwire
	Linux Shadow Password HOWTO

Permanent connection

High-speed Internet access offers many advantages, among which you can note that you do not have to reconnect every time you wish to connect to the Internet. Contrary to the commuted telephone link, you are indeed on Internet as soon as your computer is on and that your operating system is in action.

In all cases of permanent connection, whether it involves a cable modem link via a local network at work or differently, you must remember that unless you deactivate it when it is not needed, the resource sharing function in your system remains active, even when you are no longer using the Internet. If you must absolutely activate the resource sharing function, take the necessary measures and deactivate it as soon as possible. It is also recommended not to leave your computer connected to the Internet at all times without an adequate protection.

In summary:

• Do not activate your computer resource sharing when you are connected to the Internet.
• If you must absolutely activate your resource sharing function:
  • protect its access with a password which is difficult to decipher;
  • limit permissions granted to bare essential (printing, restricted files, read only);
  • do not leave resource sharing permanently activated, and deactivate without delay;
• Pay attention to your operating system's messages (  et under Windows, under Mac OS 8).
• Do not install Web, Proxy, FTP servers, or other services granting access to your computer.
• If you use a remote control software similar to pcAnywhere :
  • protect your computer access with a username and a password difficult to decipher;
  • specify in your configuration the IP address of the user to whom you have granted remote control access prior to activating the remote control function.
• If you must absolutely open certain accesses to your system, consider specialized protection tools and get familiar with their configuration.
• Do not leave your computer connected to the Internet at all times without adequate protection.