Everyday defences: updates, antivirus, firewalls and least privilege

Good security is rarely one clever tool. It is a handful of ordinary habits that overlap, so that if one fails another catches the problem. In this lesson you will check the protection already built into your laptop, learn what each part really does, and set up the habits that stop the large majority of everyday attacks.

Defence in layers

A castle has a moat, a wall, a gate, guards and a keep. No single layer is perfect, but an attacker must get through all of them. Computer security works the same way. The layers you control are: updates that close flaws, an antivirus that spots known bad files, a firewall that controls traffic, a limited account that limits damage, careful downloading and, last of all, backups that let you recover from whatever got through.

Updates: the cheapest defence

When researchers find a flaw in software, the maker publishes a fix called a security patch, usually inside an ordinary update. Once the fix is public, criminals study it to learn what the flaw was and attack computers that have not applied it. So the days after an update appears are the most dangerous time to be out of date. Installing updates is the single most effective thing most people can do.

What antivirus and firewalls actually do

An antivirus programme compares files with a list of known bad patterns and also watches for suspicious behaviour, such as a programme suddenly locking many files. It is good at known threats and weaker against brand new ones. It does not protect you from giving your password to a fake website, because no bad file is involved.

A firewall controls which network connections are allowed in and out of your computer, like a doorman who checks who may enter. It blocks unrequested connections from outside. It does not look inside the files you willingly download.

Least privilege: do daily work with a limited account

Least privilege means giving a person or programme only the rights it needs and no more. On a computer, an administrator account can change anything, including installing software for everyone. A standard account can use programmes and save files but cannot make deep changes without a password.

If you browse the web as an administrator and a malicious file runs, it can do as much damage as you can. If you use a standard account, the damage is usually limited to your own files. Ubuntu already works this way: your daily programmes run without full rights and ask for your password for system changes. On Windows 11, the account created during setup is often an administrator, so some people create a second administrator account for installs and use a standard one for daily work.

Download safely

Most unwanted software enters through downloads. Use the safe routes in this order: the system's own store or updater (App Center on Ubuntu, Microsoft Store on Windows), then the maker's official website that you reached by typing the address or from a search result you checked. Avoid download sites that surround a download button with several others, “cracked” paid software and “free” versions of films or games. When you install, read each screen; optional extras are a common way for adware to ride along.

Backups: the last line of defence

Some attacks will get through whatever you do, and hardware also fails and gets lost. A backup is a separate copy of your important files that an attack cannot reach. Keep at least one copy off the computer, and if it is on a drive, disconnect that drive after copying so ransomware cannot reach it. The details of planning and restoring backups are in the backup lessons; here, remember that a backup you have never tested is only a hope.