Viruses
What is a virus?
What is a trojan horse?
Tips for avoiding viruses.
What IIT has done.
Checklist for safe computing.
Where you can get more info.
What is a virus?
A computer virus is a self-replicating program containing code that explicitly copies itself and that can "infect" other programs by modifying them or their environment such that a call to an infected program implies a call to a (possibly evolved) copy of the virus. There are two special categories of viruses that are common today, macro viruses and worms. Computer viruses are never "naturally occurring"; they are always man-made. Once created and released, however, their spread is not directly under human control.
- Macro Viruses
A macro is a piece of code that can be embedded in a data file. Some word processors (e.g., Microsoft Word) and spreadsheet programs (e.g., Microsoft Excel) allow you to attach macros to the documents they create. In this way documents can control and customize the behavior of the programs that created them or even extend the capabilities of the program. For example, a macro attached to a Microsoft Word document might be executed every time the document is saved and cause the text of the document to be run through an external spell checking program.
A macro virus is a virus that exists as a macro attached to a data file. In most respects macro viruses are like all other viruses. The main difference is that they are attached to data files rather than executable programs. By some estimates 75% of all computer viruses now in existence are macro viruses. Word macro viruses continue to cause most of the problems at St. Olaf. Unless otherwise necessary, you may wish to disable macro processing.
- Worms
Worms are very similar to viruses in that they are computer programs that replicate themselves and often, but not always, contain some functionality that will interfere with the normal use of a computer or a program. The difference is that unlike viruses, worms exist as separate entities; they do not attach themselves to other files or programs. Because of their similarity to viruses, worms are often also referred to as viruses.
What is a Trojan Horse?
A "trojan horse" is a program that does something undocumented which
the programmer intended, but that the user would not approve of if he
or she knew about it. According to some people, a virus is a particular
case of a Trojan Horse, namely one which is able to spread to other programs
(i.e., it turns them into Trojans too). According to others, a virus
that does not do any deliberate damage (other than merely replicating)
is not a Trojan. Finally, despite the definitions, many people use the
term "Trojan" to refer only to a non-replicating malicious program.
Some tips for avoiding computer viruses
A computer virus is a program and not a microorganism, but it is infectious and can be highly complex. Viruses implant instructions in other programs or storage devices that can attack, scramble, or erase computer data. The virulence of computer viruses lies in their ability to replicate themselves and spread from system to system. Few computing systems seem to be immune to infection.
High risk behaviors
The following activities are among the most common ways of getting computer viruses. Minimizing the frequency of these activities will reduce your risk of getting a computer virus:
- Freely sharing computer programs and system disks
- Downloading executable software from public-access bulletin boards
- Opening email attachments from people you don't know
Signs of a virus infection
If your computer begins to do things out of the ordinary, or if it stops being able to do things it has always done in the past, it may be infected by a virus. It is important, though, to distinguish between virus symptoms and those that come from corrupted system files, which can look very similar. Remain calm and objective, and rule out more standard causes before suspecting a virus.
What IIT has done
IIT has made virus detection software available on St. Olaf-owned computers.
- All desktop machines should have Symantec Anti-Virus installed. Virus definitions are automatically updated on desktop machines.
- Installed Symantec Anti-Virus software on the central servers to scan all files on the network for virus infections
- All incoming e-mail is scanned for viruses and the virus (usually found as an attachment to a message) is removed before delivery.
If you don't have virus detection software on your desktop computer, you can install it. If you need assistance installing it, contact your IIT staff representative, come to RML251, or call the HelpDesk (x3830)
A checklist for safe computing
Prevention is a matter of vigilance and avoiding contact with unknown disks. It is usually the unwary who get computer viruses. Following is a list of some recommendations for safe computing:
- Make sure your office computer and your home computer have virus detection software. There are two general functions that anti-virus programs perform: scanning for and removing viruses in files on disks, and monitoring the operation of your computer for virus-like activity (either known actions of specific viruses or general suspicious activity). Most anti-virus packages contain routines that can perform each kind of task.
- Regularly back up your files. Viruses are one more very good reason to back up your files.
- Keep your original application and system disks locked (or write protected). This will prevent the virus from spreading to your original disks.
- If you must insert one of your "application-floppies" into an unknown machine, lock (write protect) it first, and unlock your application disk only after verifying that the machine is "clean".
- Obtain public-domain software from reputable sources. Check newly downloaded software thoroughly using reputable virus detection software on a locked floppy disk for any signs of infection before you copy it to a hard disk. This can also help protect you from Trojan Horse programs.
- Open email attachments only from people you know. And even when you do that, be on the lookout for virus-infected attachments.
- Quarantine infected systems. If you discover a system is infected with a virus, immediately isolate it from other systems. In other words, disconnect it from any network it is on and don't allow anyone to move files from it to another system. Once the system has been disinfected, you can copy or move files.
(Note: if you back up a file that is already infected with a virus, you can re-infect your system by restoring files from the backup copies. Check your backup files with virus scanning software before using them.)
Where you can get information about current viruses
If you want to learn more about viruses we recommend:Where you can get information about current virus hoaxes
Final thought
Be sure to contact your IIT staff representative, come to RML251, or call the HelpDesk (x3830) if you need further assistance concerning computer viruses.