The word “malware” is derived from two terms: “malicious” and “software.” Software is what operates the hardware, or physical components, of your computer. Malicious—well, you probably know what that means. Hateful, spiteful, mean, nasty, mischievous, and, well, you get the idea. It does bad things to your computer, or makes your computer do bad things. Malware is wide-ranging enough to be categorized. Here are a few categories of malware:

Virus – Designed to disrupt legitimate programs on your computer. It has the ability to replicate itself.

Spyware – Software that may take information from your computer without your knowledge and sends it to others.

Worm – Software that does not alter files but duplicates itself in active computer memory and affects your ability to use your computer.

Trojan horse – Computer code that may be  hidden in another program. When the program is run, the malicious software installs itself on the victim’s computer.

Keylogger – A program that records the keystrokes on the victim’s computer keyboard. The information can be sent to another person who may use it to log in to a victim’s online accounts.

Screen capture – A program that takes snapshots or “captures” of your computer screen and sends them to the hackers. The program can allow the hackers to see the various websites you are visiting. Used in combination with keylogger, it can give the hackers everything they need to steal login credentials to your accounts.

Cryptolocker – A program that can encrypt or lock all of the files on a computer. It is usually used to extort victims for a ransom payment to unlock the files.

Camfecting malware – This is a software program that has a specific ability to turn on your webcam, allowing a hacker to peer at you or anyone who in the room where your computer is located. Some of the programs can activate the webcam without triggering the light that indicates the webcam is turned on.

Scareware – Software that causes messages to appear on your computer indicating that your computer is infected with malware. It is infected, by the scareware, but the hackers are not referring to that. They falsely claim there is an infection that they can fix if you pay them money.

There are a few different ways you can get malware on your computer. Many times, it involves clicking on links, attachments, or emails that surreptitiously download it to your computer. Once this happens, bad things can occur. For example, in the case of keystroke logging, the malware records keystrokes as the victim types them. It may have the capability to send them to the hackers. If these keystrokes are the usernames and passwords to your online accounts, the hackers may then have the credentials needed to log in to those accounts. How do they know what sites you were logging into? With screen capture malware. Both screen capture and keylogger work in the background and you have no idea it’s even happening. It does not affect your ability to log in to your accounts; you can still do that. But so can the hackers, because they will have your login credentials that were stolen by the keylogging software!

In many cases, the delivery system for malware is through emails. To avoid malware delivered through email, your best defense is to not click on links or attachments in emails that fall into these categories:

Emails from unknown senders. Here is a simple rule. If you receive an email from someone whose name you don’t recognize, don’t click on a link or attachment in that email.

Emails that look suspicious. If you receive an email from someone you know but all it contains is a link, don’t click on the link. It is likely, under this circumstance, that the email account of the sender has been compromised. The hackers may be trying to use the hijacked email account to spread malware.

Emails that don’t make sense. Before clicking on a link or attachment in an email, ask yourself a key question: does this email make sense? For example, I received an email in which the sender was listed as “The Internal Revenue Service.” The contents of the email indicated that my taxes from a previous year were in “arrears.” There was an attachment in the email labeled “calculations” and instructions in the email to open that attachment.

Of course, an email like this may elicit an emotional reaction from the receiver, who may think they owe the IRS some money. But if you stop and think about it, the email itself doesn’t make sense. If you really do owe money to the IRS, their first notification to you is not going to come in the form of an email. It will be physical mail delivered by the

U.S. Postal Service. Your notification will not be in the form of a text message, Facebook update, Tweet, Snapchat photo, Vine video, or email!

If the email you are reading doesn’t make sense, don’t click on anything in the email.

Besides using emails to infect victims’ computers with malware, hackers use other techniques.

Malware bundled with other software. Sometimes you may opt to download software to a computer from a website.

The software you seek may be legitimate and serve a desired purpose. However, you should only download software from a legitimate vendor’s site and make sure you know exactly what you are installing. Uncheck any boxes offering to download extra programs with your desired program. Don’t just click “OK” throughout the download process. Carefully inspect what you are agreeing to and don’t agree to anything except the software you wanted in the first place.

Peer-to-peer networks. Websites that allow you to share files with other user’s computers have known issues with spreading malware. Avoid these sites. If there are people in your family who use peer-to-peer networks, do not use the same computer that they do for sensitive tasks like online banking or even email. It would be best to have a separate computer used only for peer-to-peer activities, if you must use them at all.

Infected websites. Sometimes legitimate websites may become compromised. In this case, visitors to these sites may unknowingly have their computers infected just by visiting the sites, which can take advantage of known vulnerabilities on your computer. We have no control over the security of the websites we visit. But we do have control over our own computers’ security. Your best defense here is to keep your all of your software updated, which will reduce your vulnerabilities.

Infected removable drives. Sometimes devices we plug into our computer can contain malware. These devices include portable hard drives and USB flash drives. Your best defense is to disable auto-run features for these devices. This can be done in your computer’s settings. If you do plug a device into your computer, you should run a malware scan with your anti-virus software before any programs can run from the drive.

There are many ways (or, as security professionals say, “vectors”) for a malware attack. Your best defense for each threat vector has been described above. Besides those specific defenses, it is important that computers be protected with a general antivirus program that is kept up to date. There are many brand names in the antivirus market. There are free versions and paid versions. Generally, it has not been proven that any one brand works better at defending your computer than another, nor that the free versions are less secure. However, paid versions of antivirus programs usually offer more features that could provide more protection under certain circumstances.

If you have a Windows PC, you might also consider the antivirus program that is included with Microsoft versions 10 and 11. It is provided for free. It is called Windows  Defender  and  it  is  included  in  the  Windows Essentials  software

If you happen to own a Mac, be advised that Apple computers are not immune to malware and users should use protective software for these products.

Remember, antivirus programs are not infallible, but they are our first line of defense and create a perimeter shield against hackers. Because of their fallibility, you do need additional protection. What is the additional protection, you ask? You. It’s your vigilance, and it’s your behavior online. Avoid risk, be careful, and keep your computer secure.