As stated earlier in this chapter, malware is an extremely broad term that blankets a range of software packages. We can say that malware is anything that steals resources, time, identity, or just about anything else while it is in operation. In order to understand what malware is, let’s look at the major types before we delve deeper into the mechanics of each:
- Viruses are by far the best-known form of malicious software. This type of malware is designed to replicate and attach itself to other files resident on the system. Typically, viruses require some sort of user action to initiate their infectious activities.
- Worms are a successor to viruses. The worm has been around in some shape or form since the late 1980s. The first worms were primitive by today’s standards, but they had a characteristic that is still seen today: the ability to replicate on their own very quickly. Worms that have emerged over the past decade or so have been responsible
for some of the most devastating denial-of-service attacks known.
- Trojan horses are a special type of malware that relies in large part on socialengineering techniques to start infecting a system and causing harm while appearing to look like a legitimate program. Similar to a virus in many respects, this malware relies on the user being somehow enticed into launching the infected program or wrapper, which in turn starts the Trojan.
- Rootkits are a modern form of malware that can hide within the core components of a system and stay undetected by modern scanners. What makes rootkits most devastating is that they can be extremely difficult to detect and even more difficult to remove.
- Spyware is malware designed to gather information about a system or a user’s activities in a stealthy manner. Spyware comes in many forms; among the most common are keyloggers.
- Adware is malware that may replace home pages in browsers, place pop-up ads on a user’s desktop, or install items on a victim’s system that are designed to advertise products or services.