Computer Virus, Spyware, and Annoyances FAQ

This set of frequently asked questions (FAQ)  answers questions about computer viruses, spyware, adware, and other dangerous and annoying characteristics of modern computing.  These answers are predominately aimed at home and small business users with single computers or a small to medium sized network. 

Please note that this is a rapidly changing field and there are sometimes no definitive definitions and answers for some of the questions asked.  This FAQ is our best attempt to provide an overview of the subject, but it is not a substitute for asking an expert.

1.  What is a computer virus?

2.  What are the types of viruses?

3.  What is a Trojan Horse?

4.  What is a worm?

5.  What is spyware?

6.  What is adware?

7.  Are the "pop-up" ads I get when I visit web sites the result of an adware application running on my machine?

8.  How are viruses. worms, etc. spread?

9.  What can I do to protect my computer from all of this?

10.  Where can I get information about a specific virus or hoax?

If you have any other questions, please contact us.

1.  What is a computer virus?

A computer virus is a program that infects a computer's disk drive, files, and/or programs.  A virus also replicates itself in order to infect more computers.  Many viruses simply replicate and infect and do not do any damage to the infecte4d machines.  Others can create significant amounts of damage by changing files, erasing programs (or entire disks), or by using the infected computer to attack other computers. 

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2.  What are the types of viruses?

Common types of viruses include the following.

Macro - In a macro virus the virus is contained in a "macro" or "script" that is part of a document such as a word processor file or a spreadsheet.  For example, both Microsoft Word and Microsoft Excel support macros that are, in effect, attached to a document.  Macros are small programs that perform some particular task and are very useful.   Macro viruses are spread by sharing document infected files.  After your computer is infected with a macro virus, subsequent documents you create or open may also be infected with the virus.  Macro viruses are a frequent source of virus infections.

Boot Sector - The boot sector is a special area on a hard drive or diskette that is used to start the operating system.  Boot sector viruses infect this area so that they can 1) be replicated through the sharing of disks. and 2) executed when the disk is accessed.  Note that boot sector viruses can be spread even if a diskette, foe example, is not a bootable diskette. 

Program or Executable -  These are viruses that are spread by sharing program files.  Programs files (like the exe and dll files associated with most applications) and not shared as often as documents, and this cuts down on the number of these types of viruses. 

Hoaxes  - These are not actually virus programs. They are email messages that  warn about a supposed new virus.  These false warning messages usually encourage the recipient to send the warring to everyone they know know.  Even though these hoax warnings are sent by well-meaning people and carry no real virus software, they are a real problem since they can cause large amounts of Internet traffic and unnecessary calls to tech support personnel.  

Email - These are similar in appearance to hoaxes, except they carry instructions for deleting a virus or fixing a problem created by the virus and the proposed solution actually deletes needed files or does other damage to your computer.  The theory is that you get this warning form someone you trust (perhaps the same well-meaning friend that sends out the hoaxes), you check and find the supposedly dangerous file on your machine, you decide to "fix" your computer by following the instructions, and you delete a needed file.

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3.  What is a Trojan Horse?

A Trojan Horse is a virus hidden in what appears to be a regular program.   They differ from the program or executable viruses described above because they do not try to replicate themselves.  The program in which the Trojan Horse code resides may perform an actual function and the user may not realize that their computer has been compromised.

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4.  What is a worm?

A worm is a virus that copies itself throughout a computer's disk and memory.  The difference between a regular virus and a worm is that worms exist as separate programs - they do not "hitch-hike" on other files or programs.  Worms can take advantage of automatic file sending and receiving features found on many computers and can spread itself automatically over a network from one computer to another.  Worms can replicate themselves to the point that they use up the computers resources and eventually bring the system down.

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5.  What is spyware?

Spyware is a piece of software that monitors a computer's activity with the intent of finding out about the user and their usage habits.  Spyware is often used to Often used to log a user's Internet Web surfing habits.  This information is then sent (mostly without the users knowledge or permission) to a collection site that can make decisions about ads to show the user, create a marketing profile for the user, sell the information about the user, etc. 

Spyware is often built into free downloads from the Web and the user may be giving permission for its use on a machine.  The notice of the download and the the permission is embedded in the license agreement that users often accept without reading.

There is currently a significant amount of spyware around and it is safe to say that it is installed and operating on very many computers.

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6.  What is adware?

Adware is similar to spyware in that it runs (often without your explicit knowledge or permission) on your computer.  Adware is used to occasionally display ads on your machine based on web sites you have visited or your interests as indicated by your browsing habits.   (Adware and spyware are similar enough that there are debates regarding the proper designation for many of the applications.)

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7.  Are the "pop-up" ads I get when I visit web sites the result of an adware application running on my machine?

Maybe.  Some sites use adware applications and others simply pop-up the ads (either in the current browser window or in a new window) anytime you visit.  We consider pop-ups to be in a catgory by themselves because they do not require any "helper" code (like adware) to run on your machine and because they seem to be everywhere.  Unfortunately. most of the programs that stop adware do not stop pop-ups.

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8.  How are viruses, worm, etc. spread?

A common mechaniSMfor spreading a virus is e-mail.  The virus is not in the e-mail message itself, but is in an attachment.  The attachment may be a program or may be a document infected with a macro virus. 

Another common method is by obtaining a file (either a program or document) off a floppy or CD or by downloading from the Internet.  Notice that some spyware and adware programs are downloaded when you download other programs that you want (and that you may be agreeing to this in the "fine print" of the End User License Agreement.)

Some viruses spread without user help.  They use system file transfer mechanisms or e-mail programs to replicate themselves.

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9.  What can I do to protect my computer from all of this?

Unfortunately, there is no simple answer.  There is no single solution that protects against all threats. 

The following table provides an over view of some of the actions you can take and the products we suggest you consider.

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9.  Where can I get information about a specific virus or hoax?

The Symantec Security Response web site provides information on currently active threats as well as an "encyclopedia" where you can look up virus and hoax information.

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