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New computer viruses
seem to make the news just about every month. Since this trend is likely
to continue, it’s important to understand what computer viruses
are, how they work, and what you can do to protect your computer from
becoming infected.
What is a
computer virus?
A computer virus is a software program that copies itself to your computer
without your knowledge and causes some unexpected and usually unwelcome
change to your computer. A virus can damage data, cause your computer
to crash, play a joke, or display unwanted messages.
Viruses can be transmitted to a computer from a disk,
a CD, a website, an e-mail attachment, a shared network drive, or a
file downloaded from the Internet. Some viruses inflict their damage,
also referred to as their "payload," as soon as the code is
executed. Other viruses may lie dormant until a specific event activates
the code.
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Common
types of computer viruses
A variety of computer viruses can infect a machine. The most common
types of viruses are explained below. Keep in mind, however, that a
particular virus may also share the characteristics of one or more virus
types.
- Boot sector virus
The boot sector is the area on a disk containing programs that are
executed when you start your computer. A boot sector virus, also known
as a system sector virus, infects the original boot sector on a floppy
disk. The virus can be transmitted to another floppy disk or to the
hard drive on a computer. Since this virus spreads before any virus
protection code on your machine can be activated, a boot sector virus
is particularly serious if the virus infects the master boot record
on a computer's hard drive. Recent boot sector viruses include Monkey
A or B and Anti Exe Ripper.
- Dropper virus
A dropper virus is an executable file (.EXE) that infects a computer
when the file is executed or run. Therefore, when a dropper file is
scanned for viruses, the scan does not detect the virus because the
virus code has not been created. The Navidad virus, which spread at
the end of 2000, is an example of a dropper virus.
- File infector
A file infector attaches itself to or associates itself with a file.
This type of virus can append itself to regular program files, overwrite
program code, and associate itself with specific program filenames.
When the infected program is run, the virus is transferred to a computer's
hard drive and, in some cases, the virus will replicate itself. File
infector viruses such as Casper, Junkie, and 2014 have infected numerous
computers.
- Macro virus
A macro is a set of instructions for automating repetitive or complex
tasks in applications, such as Microsoft Word or Excel. When a file
containing a macro virus is opened, the virus can execute destructive
commands. The Melissa virus that spread in 2000 is an example of a
macro virus.
- Stealth virus
As its name implies, a stealth virus uses one or more techniques to
avoid detection. A stealth virus can also conceal an increase in file
length by displaying the original, uninfected file length. Recent
stealth viruses include Windmill and SMILEYBO.
- Trigger
A trigger virus is activated when a particular event occurs. An event
can be identified by markers such as a date or a sequence of keystrokes.
When a trigger event occurs, it activates the virus which then infects
the computer. Anti-virus programs cannot detect a trigger virus until
that event occurs. The Chernobyl (CIH) virus activated on April 26,
1999, the 13th anniversary of the Chernobyl disaster, is an example
of a trigger virus.
- Joke program
A joke program pulls a prank when the file containing the program
is opened. Even though a joke program is not really a virus, it has
the potential to become a virus if someone modifies the code to have
the joke drop a virus on a machine. Although joke programs may be
playful in their intent, they can also be very annoying. For example,
a joke program that affected many computers in 2000 caused the CD-ROM
drive to open when a computer was started.
- Hoax
A hoax usually takes the form of an e-mail warning about a virus.
Even though a hoax is not a virus, it has the potential of becoming
a virus if someone attaches a file containing a virus to the e-mail
message. For example, you may remember the Wobbler hoax which spread
to many computers.
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Protecting
your computer
You can reduce the chances of your computer becoming infected by taking
the following precautions:
- Residence Hall
students will be given instructions for obtaining Symantec
anti-virus software when they arrive on campus. Please be sure
to remove any previously installed anti-virus software prior to
installing Temple's software.
- Note that when you buy an anti-virus program, you
should check your computer for viruses as soon as you install the
program.
- Update your anti-virus software
When you purchase anti-virus software, the program comes with the
virus information available at the time the program was packaged.
Since new viruses are created on a regular basis, you should check
often for updates to the program.
- Update files are sometimes called definitions or
"DAT" files. These files include virus definitions and fixes
so the program can recognize and remove different viruses. New DAT
files for current viruses are available for downloading from the product's
website. It is a good idea to visit the website frequently to check
for the most recent DAT files. Some anti-virus software will send
you a reminder. Remember, your protection is only as good as your
DAT files.
- You can download McAfee updates and DAT files either
from the McAfee or the Help Desk website.
- Scan your computer's hard drive
It is good virus protection practice to scan the hard drive at least
twice a month. The virus scan detects viruses on your computer and
allows you to delete suspicious files from your machine.
- Scan all disks
Before you open a document on a disk, you should scan the disk for
viruses even if you know the person who gave you the disk. Often a
person may not be aware that a disk contains a virus.
- Stay on the defensive
Many viruses are distributed via e-mail attachments. Therefore, you
must be alert and never open an e-mail attachment sent by someone
you do not know. Also, even if you know the person who sent the message,
don't open attachments that you are not expecting. Frequently, the
person who sends an e-mail containing a virus may not be aware that
his or her machine is infected. You might want to consider contacting
the sender to make sure that the attachment is legitimate.
- Check the Computer Services website
News about the latest computer viruses is available on the Computer
Services website.
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If
your machine becomes infected
If you do not have an anti-virus program on your computer and your machine
becomes infected, you should purchase anti-virus software and update
it immediately. In most cases, the anti-virus software will remove the
virus. If the software does not remove the virus, you can check anti-virus
websites, such as Symantec or McAfee, either for directions on manually
removing the virus or for programs that will remove the virus for you.
If you still cannot remove a virus from your machine, you can contact
the Computer Services Help Desk at 215-204-8000 or
send e-mail to: help@temple.edu.
The Help
Desk hours are posted on Help Desk website.
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Want to learn
more?
Computer Services periodically offers a seminar entitled "Protecting
Your Computer from Viruses." For seminar dates and times, visit
the seminar website.
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