Summary

Malware, short for "malicious software", is a term used to describe any software or program intentionally developed to attack and destroy a computer system's integrity by exploiting security holes in either one of the installed applications or the operating system itself.

Purpose

Many early malicious programs were developed only as experiments or pranks generally intended to be harmless. However, with the widespread use of Internet, malicious software has come to be designed for a profit motive, such as making unauthorized transfer of funds, stealing of personal and confidential information, etc.

Major Types of Malware

Viruses

The most widely known type of malware is a computer virus. The term computer virus is used for a piece of code that attaches itself to the system in such a way that allows it to self-replicate anytime the executable program, to which it is attached, is used.

Many viruses often contain payloads that may erase the data files or damage them to such an extent that the data would become completely useless.

The most common categories of a computer virus include Boot Sector Virus, File Virus, and Multipartite Virus. To learn more about individual categories of viruses, follow this link.

Worms

A computer worm, in concept, is the same as a virus. A worm reproduces and spreads itself but, unlike a computer virus, it actively transmits itself over a network and does not attach to any executable program.

Although the terms virus and worm are sometimes used interchangeably, but the difference between the two is the manner in which they spread. A virus requires user intervention to spread, whereas a worm spreads automatically.

Trojans

Trojan, widely known as Trojan Horse program, is a piece of code that disguise itself to a computer user as something desirable, but infact contains a malicious payload which causes damage to the computer.

One of the most common ways that spyware is distributed is as a Trojan horse, bundled with a piece of desirable software that the user downloads from the Internet. When the user installs the software, the spyware is installed alongside.

Rootkits

Once a malicious program is installed on a system, it is essential that it stay concealed, to avoid detection and disinfection. Techniques known as rootkits allow this concealment, by modifying the host operating system so that the malware is hidden from the user. Rootkits can prevent a malicious process from being visible in the system's list of processes, or keep its files from being read.

Originally, a rootkit was a set of tools installed by a human attacker on a Unix system where the attacker had gained administrator (root) access. Today, the term is used more generally for concealment routines in a malicious program.

Spyware

Any non-replicating software installed on a computer that tracks a user's activity without his/her knowledge can be classified as a spyware.

Spyware runs hidden in the background and monitors a user's Internet surfing habits, such as the kind of websites being visited, files being downloaded, etc. Spyware may also gather a user's confidential information such as e-mail addresses, credit card information, bank account details, login information, or any other useful information that can be sold to third-parties.

The collected information is then typically used with adwares to target the most relevant advertisement based on the likings of the user.

Adware

Adware is a short form of advertisement supported software. It started as a way for developers to recover their development costs while still offering their software free of charge or at a reduced price.

Soon after, softwares such as Gator started using it to collect personal information from its users withour their knowledge, including all websites visited and portions of credit card numbers, in order to target and display ads on the computers of web surfers.

External Links

1. Well-known adware programs/programs distributed with adware
2. Information on computer malware, worms and any self-replicating programs.