Ask Leo! #656 – What’s the Difference Between a “Trojan Horse”, a “Worm”, and a “Virus”?

The Ask Leo! Guide to Online Privacy

This week's ad, below, is for my new book, The Ask Leo! Guide to Online Privacy. As a newsletter subscriber I wanted to make sure you were aware of a couple of (money saving!) points:

  • Don't forget that there's a discount code in the administrative section of each emailed newsletter that'll get you 20% off, on top of the current sale price.
  • If you're an Ask Leo! Patron at the $5/month level (aka "Bronze") or higher, you already have a digital copy of the book. :-) Just login to your members.askleo.com account, visit your "My Library" page and you should see it listed there for you to download.

I appreciate your support, and I don't want you paying for more than you should. :-)

What's the Difference Between a "Trojan Horse", a "Worm", and a "Virus"?

(skip)

There's no shortage of confusing terminology in the computer biz. With the advent of malicious software, more terminology has been created that only make things less clear.

The good news is that it's not really that difficult; in fact, you needn't understand most of the details (besides, not everyone agrees on the exact meaning of each definition).

Let's run down a few terms.

Malware

The most important term to know is malware, which is short for malicious software.

The name says it all: malware is any software that has malicious intent — destroy data, send spam, hold your data for ransom, steal your information — it doesn't matter. It's all malicious, it's all software; thus, it's all malware.

You'll find malware used as a catch-all term for all flavors and varieties of software that intend some kind of harm.

Virus

In the human body, a virus is an organism that replicates, or makes copies of, itself and overwhelms the body's defenses, making it sick.

When applied to computers, the term "virus" is very similar.

  • A computer virus replicates itself in some way so as to spread within the computer, usually injecting itself into other programs within the computer.
  • A computer virus makes the infected computer "sick". In the computer sense, "sick" can mean poor performance, crashes, lost files and data, or more.

Very technically, the term virus does not necessarily imply that a piece of malicious software will replicate itself to other systems. In general use, it's assumed.

Spyware

Spyware is a type of malicious software intended not to do damage, but to collect information, or "spy", on you. Spyware might monitor and report back on your browsing habits and the programs you run, or access and send other information stored on your machine. One canonical form of spyware is the keystroke logger, which, as its name implies, records your keystrokes (and often more) and uploads this information to a third party.

Worm

A worm is a program that replicates itself to other computers. It does so by infecting media, such as USB drives, that make contact with multiple systems, transmitting itself over a network somehow, or otherwise copying itself from one computer to another.

Very technically, again, the term worm does not necessarily imply malicious intent or behavior, other than the replication. In practice, malicious intent is generally assumed.

Trojan Horse

A Trojan horse — often just a "trojan" — is a program that claims to be one thing but is, in fact, another. It uses that deception to gain access to a system that would not be given, were the true intent known.

A trojan horse is not a virus per se, but it may carry them. For example, there are trojans that claim to be patches for various problems, but instead (or in addition) install malware. Software obtained from many download sites is often a type of trojan, using the promise of the software that is desired to install additional malicious software that is not.

Phishing

I think of phishing as a kind of email-based trojan horse. It's email that looks like it comes from some official site, such as your bank, PayPal, or eBay, but actually comes from someone pretending to be them. They typically use some technique to fool you into thinking they are an official site of some sort, so you hand over sensitive information, like your username and password. Once you do so, they steal your other information, often leading to hacked accounts, identity theft, or worse.

Regardless of the terms used, protect yourself

The terms are important, but they're less important than being aware that malicious software — malware — exists, and taking the steps you need to take to keep yourself safe.

We shouldn't have to, of course. Hackers shouldn't exist, and operating systems and other software should be designed to perfectly protect us. The pragmatic reality, however, is that it remains our responsibility to keep our guard up.

What does that mean? As outlined in what I consider my most important article — Internet Safety: 7 Steps to Keeping Your Computer Safe on the Internet — it all boils down to using common sense, keeping your software as up-to-date as possible, and running up-to-date anti-malware tools regularly.

Related Links & Comments: What's the Difference Between a "Trojan Horse", a "Worm", and a "Virus"?
https://askleo.com/2201

The Ask Leo! Guide to Online Privacy

There's no avoiding the issue: privacy issues are scary, complex, and even somewhat mystifying.

The Ask Leo! Guide to Online Privacy tackles these topics in terms you can understand. The Ask Leo! Guide to Online Privacy will help you understand what's at risk, what steps to take, and what to do when you're not sure.

ON SALE!

For one week only, the digital edition of The Ask Leo! Guide to Online Privacy is 20% off!

The Ask Leo! Guide to Online Privacy

I've Been Told My Computer Has a Virus, But My Anti-Malware Program Doesn't Remove It. What Do I Do?

I get variations of this question often. Someone has correctly determined their computer has some kind of malware, either by symptoms or some other means, but the anti-malware program they're running fails to detect it — or perhaps detects it, but fails to repair it.

It's a race, folks, and sometimes your security software isn't in the lead.

Continue Reading: I've Been Told My Computer Has a Virus, But My Anti-Malware Program Doesn't Remove It. What Do I Do?
https://askleo.com/2015

Pinboard - Never Lose Bookmarks Again

You may notice I rarely talk about browser-based bookmarks (also called "favorites").

That because I rarely use them. Instead, I use Pinboard, an online service that saves my bookmarks for me.

Let's review the problems with browser-based bookmarks, and why a service like Pinboard is such a powerful alternative.

Continue Reading: Pinboard - Never Lose Bookmarks Again
https://askleo.com/28122

The Ask Leo! Tip of the Day

A feature exclusively available to Ask Leo! Patrons Bronze level & above.

More Ask Leo!

Become a Patron
Books - Business - Glossary
Facebook - YouTube - More..

Leo's Other Projects....

HeroicStories Since 1999, HeroicStories brings diverse, international voices to the world ' reminding us that people are good, that individuals and individual action matter. Stories - new and old - are published twice a week.

Not All News Is Bad - Each day I look for one story in the current news of the day with a positive bent. Just one. And I share it.

leo.notenboom.org - My personal blog. Part writing exercise, part ranting platform, it's where I write about anything and everything and nothing at all.

Help Ask Leo! Just forward this message, in its entirety (but without your unsubscribe link below) to your friends. Or, just point them at https://newsletter.askleo.com for their own FREE subscription!

Newsletter contents Copyright © 2017,
Leo A. Notenboom & Puget Sound Software, LLC.
Ask Leo! is a registered trademark ® of Puget Sound Software, LLC

Posted: June 13, 2017 in: 2017
Shortlink: https://newsletter.askleo.com/7697
« Previous post:
Next post: »

New Here?

Let me suggest my collection of best and most important articles to get you started.

Of course I strongly recommend you search the site -- there's a ton of information just waiting for you.

Finally, if you just can't find what you're looking for, ask me!

Confident Computing

Confident Computing is the weekly newsletter from Ask Leo!. Each week I give you tools, tips, tricks, answers, and solutions to help you navigate today’s complex world of technology and do so in a way that protects your privacy, your time, and your money, and even help you better connect with the people around you.

The Ask Leo! Guide to Staying Safe on the Internet – FREE Edition

Subscribe for FREE today and claim your copy of The Ask Leo! Guide to Staying Safe on the Internet – FREE Edition. Culled from the articles published on Ask Leo! this FREE downloadable PDF will help you identify the most important steps you can take to keep your computer, and yourself, safe as you navigate today’s digital landscape.



My Privacy Pledge

Leo Who?

I'm Leo Notenboom and I've been playing with computers since I took a required programming class in 1976. I spent over 18 years as a software engineer at Microsoft, and after "retiring" in 2001 I started Ask Leo! in 2003 as a place to help you find answers and become more confident using this amazing technology at our fingertips. More about Leo.