As the internet has become more integrated into society over the years, the presence of malware (short for 'malicious software) has increased as well. We may have much better ways of defending ourselves from them today, but even the most savvy computer user who practices the safest of browsing habits can still end up being infected with malware occasionally.
Most people have heard the words 'spyware', 'virus' and 'trojan' thrown around a lot, but most don't realize there are actual differences between them. Here's a quick rundown of the most popular forms of malware out there today.
Spyware - Most malware today exists as spyware. Unlike viruses and trojans which are built to disable a computer, spyware usually does not harm your computer aside from slowing it down a bit. Its purpose is usually to extract vital information from your computer such as credit card numbers, bank account info, passwords and other information that could supply someone with the ability to steal your identity and your money.
Adware - Adware are programs that install themselves on your system and then spam it with advertisements. Sometimes they will even disable your system and request that you pay money to get rid of the 'virus' preventing it from working by using the companies fake anti-virus software. Adware can get automatically downloaded to your system while browsing any website and can be viewed through pop-up windows or through a bar that appears on a computer screen automatically. Adwares are common because many companies hire coders to create them for marketing purposes.
Virus - A virus is a program written to enter to your computer and either damage or alter your files in some way. This can cause corruption or delete data so viruses are generally the most dangerous type of malware. It can also copy itself onto any other vulnerable machines on your network meaning one virus can potentially disable an entire household of computers.
Trojans - These are similar to viruses but the key difference is that they do not replicate themselves. It is a destructive program that appears as a genuine application. Trojans can also open a backdoor entry in your network or firewall which gives malicious users/programs access to your system, allowing confidential and personal information to be stolen without you ever knowing. They can be hidden in a free/trial software or other files that you download.
Keyloggers - A keylogger or 'keystroke logger' is a program that monitors each keystroke a user types on their keyboard and sends the data of those keystrokes to a third party so they can analyze it for passwords and other sensitive information. They are the leading cause of account hijackings with games, PayPal accounts, etc and they can be especially hard to detect with just normal anti-virus measures.
Worms - Worms make copies of themselves again and again on the local drive, network shares, etc. Unlike a virus, its only purpose is to reproduce itself again and again eventually taking up the entire hard drive. They usually do not need to attach themselves to executable and instead spread themselves by exploiting vulnerabilities in operating systems.
Malware is one of the major causes of slow downs and they usually operate under the radar so it won't necessarily be obvious that you are infected with them until it's too late. Luckily, many infections can be eliminated and the damage reversed by a professional.