Computer security is used to protect information from unauthorized access or change
People want to keep their computers, phones, and tablets secure. That means that they do not want to have their sensitive information, like bank account data, stolen or changed without their permission.
People, governments, companies, and other organizations all want their computer systems to be secure. They also want to be able to access their computers and information whenever they need to.
Computer security is commonly referred to as having three key dimensions: Confidentiality, Integrity, and Availability.
Confidentiality means that information is secure and private from people who should not access it
Many things are done with computers now that used to be done on paper. This computerization means that there is now a vast amount of information held by computers. Much of this information should only be available to people who are allowed to have it. For example, computer systems used by doctors, hospitals, and insurance companies hold people's private information, like social security numbers and health histories. Banking systems store bank account numbers, account balances, social security numbers, and more. Corporations keep trade secrets on computer systems. And governments keep information about government employees and officials, military staff and systems, intelligence, strategies, and much more that they would not want in the hands of other countries. Private information can be stolen, sold, used for profit, or used to harm companies or countries.
For example, multiple companies have had their payment systems hacked into and credit card numbers stolen and sold to others. Hacking is when people write computer code to get into computer systems they are not supposed to access. The people who purchase these credit card numbers often create new fake credit cards from them, and then use the credit cards to purchase things that the credit card owner does not know they are paying for. Stealing credit card numbers is a type of "cybercrime". A cybercrime is an crime that is accomplished through unauthorized access of a computer system. Confidentiality means that information can only be accessed by people who should be able to access it. Confidentiality is important not only for peoples' home computers, but also large computer systems used by companies and governments.
Integrity means that information is secure from unauthorized changes
People, companies, and governments do not want their important data to be changed by someone who should not be able to change the data. For example, a bank should protect its customers' bank accounts from theft. It should not be possible to hack into the bank and move money out of accounts without permission. Stealing money by hacking accounts and moving money to places it is not supposed to be is called "cybertheft". It is a type of cybercrime.
Availability means that a system can be accessed when needed without delay
You have probably at some point tried to access a web site and have not been able to get to it. Sometimes web sites have problems that make them unavailable. The problems could be related to problems the company is having with a web site update, for example. They may have made a change that accidentally broke something. Or, sometimes there is a problem in the network, and that can cause delays and lower performance.
But, sometimes the problem is that someone is intentionally attacking the site. One type of attack is called a "Denial of Service" (DOS) attack. That means that someone is sending many, many requests to the web site, just to make the web site run slow and become unavailabile. This attack can be done by having the requests come from many different locations at once. Sometimes other sites are used to launch the attack, and those site owners may have no idea that their systems are being used for it. A Denial of Service attach from many different locations is called a "Distributed Denial of Service" or DDOS attack. The whole goal of this type of computer system attack is to bring a system down so that people cannot access it. DDOS attacks have been used to bring down news sites, like CNN, social media sites, like Facebook, commerce sites like Amazon.com, and government sites, like the White House and the Pentagon.
A computer virus is software written to do something bad to a computer system
A computer virus is a type of software program that is written to do something bad to a computer. Sometimes the type of software that is written to do bad things to computer systems is called "malware". Malware can destroy information on your computer, or force your computer to run poorly. Or, it could be used to capture passwords for bank accounts or other systems, for example by capturing what you are typing. A computer program that sits in the background capturing what you do or type is called a "trojan horse".
A virus could to trick you into thinking that your computer has a problem, maybe through a message box that comes up when you are in a web browser. Sometimes these might give you a phone number to call to help you "fix" your problem. When you call, you will be connected to someone who will ask you for personal information. Or, they may have you do something to give them remote access to your computer (which will then let them capture passwords or do other destructive things.)
Or, a virus could lock you out of your system and data until you pay someone money, a "ransom", for them to release your computer - this is called "ransomware".
Antivirus software is a type of software that is designed to protect your computer from viruses. New viruses are created all the time, so antivirus software has to be updated all of the time, too. To keep your computers safe, be careful about Internet sites you visit, don't click on links to places you don't know much about, and don't ever enter passwords on a public WiFi hot spot. If you see a message that your computer has a virus, and tells you to call a number - don't do anything, and get an adult with some computer skills to help you. And don't ever share your passwords! Any time your computer is behaving differently and doing unexpected things, you should tell an adult. You might have a computer virus.