There are thousands of different cyber threats and thousands of variations of those same threats. We're not looking to cover all of them, simply a detailed list of ones you might encounter during your daily life on the web.
The defining characteristic of viruses is that they are self-replicating computer programs that modify other software without user consent by injecting themselves into the said programs.
Viruses are generally, but not always, created to harbor a nefarious payload to run & gather data - such as usernames, passwords, emails, contacts, etc.
However, not all viruses carry a destructive payload and attempt to hide. It's sad to say - but some viruses are created to be "annoying" and make the user's life a bit harder by having to remove them. That is not to say you should never remove them, all viruses should be considered destructive & removed as soon as detection occurs.
Most people also use the term "virus" to cover an umbrella of things, such as malware. Malware is not a virus, but the code can originate from a virus payload - meaning a virus can be downloaded onto a computer & runs its code to self-replicate; somewhere in that code is the payload for the malware. Once that code is run, the malware is installed onto the machine.
Malware, meaning Malicious Software, is any software intentionally designed to cause disruption to a computer, server, client, or computer network, leak private information, gain unauthorized access to information or systems, deprive access to information, or knowingly interferes with the user's security and privacy.
Many types of malware exist - including worms, Trojan horses, ransomware, spyware, adware, and scareware. These are the most common you might come across. I'll briefly touch on each one:
- Worm - A worm is a standalone computer program that replicates itself to spread to other computers
- Trojan horse - a Trojan horse is any malware that misleads users of its true intent. You might think you're downloading a fun free game - but in reality, you're installing malware.
- Ransomware - Ransomware is a type of malware from cryptovirology that encrypts all of the user's data & threatens to publish the user's data or permanently block access to it unless a ransom is paid. This is especially dangerous because de-encryption is nearly impossible & only 29% of users who actually pay the ransom get their data back.
- Spyware - is software that aims to gather information about a person or organization and send it to another entity. A common term for this is "keylogger", something that records your keystrokes & sends them to another user.
- Adware - is software that generates revenue for its developer by automatically generating online advertisements in the user interface of the software or on a screen presented to the user during the installation process. Typically, when you install a program that includes adware - you'll start seeing advertisement pop-ups on your desktop.
- An expanded point on this: You might think, "huh, this has happened after I've installed software I knew was safe?". Some manufacturers include adware in their otherwise safe-to-use applications to advertise new products to you.
- Botnet - A botnet is a group of devices, each of which runs one or more bots. Botnets can be used to perform Distributed Denial-of-Service (DDoS) attacks (see next point), steal data, send spam, and allow the attacker to access the device(s) & access their network connection.
- DDoS (Distributed Denial-of-Service) - denial-of-service attack (DoS attack) is an attack where the attack makes a machine or network resource unavailable to its users by temporarily or indefinitely disrupting the services of a host connected to a network. Denial of service is typically done by flooding the targeted machine or resource with fake requests as to overload the system. In a distributed denial-of-service attack (DDoS attack), the incoming traffic flooding the victim originates from many different sources (such as a botnet).
- Man-in-the-middle: is where the attacker secretly relays (and possibly alters) the communications between two parties who believe that they are directly communicating with each other, as the attacker has inserted themselves between the two parties. One example of a MITM attack is active eavesdropping, in which the attacker makes independent connections with the victims and relays messages between them to make them believe they are talking directly to each other over a private connection when in fact, the entire conversation is controlled by the attacker.
There are many cyber threats, it would be impossible to include all of them in one article. As long as you practice safe practices on the internet & implement good personal policies for computer use, you'll be as safe as you possibly can be.