Originally posted on wibc.com ob 06/11/2012
What is Malware?
Malware, short for malicious software, is software designed to secretly access a computer system without the owner’s informed consent. Malware includes computer viruses, worms, trojan horses, spyware, dishonest adware, scareware, crimeware, most rootkits, and other malicious and unwanted software or program.
Notice the use of words “informed consent” in above definition. This means malware is not defined based on its functionality only. For example, if you download and install a keylogger yourself for your own purpose, it might not classify as a malware.
What is Spyware?
Spyware is a type of malware that can be installed on computers, and which collects small pieces of information about users without their knowledge. The presence of spyware is typically hidden from the user, and can be difficult to detect. While the term spyware suggests software that secretly monitors the user’s computing, the functions of spyware extend well beyond simple monitoring. Spyware programs can collect various types of personal information, such as Internet surfing habits, sites that have been visited, etc.
Going by this logic, it would mean even the cookies that websites install can fall in this category.
What is Adware?
Adware is quite specific to displaying unwanted ads. Adware, or advertising-supported software, is any software package which automatically plays, displays, or downloads advertisements to a computer. These advertisements can be in the form of a pop-up.
What is a Rootkit?
Rootkits are one of the most technically advanced malware. They are what people normally perceive as viruses.
A rootkit is software that enables continued privileged access to a computer while actively hiding its presence from administrators by subverting standard operating system functionality or other applications. Once a rootkit is installed, it allows an attacker to mask the ongoing intrusion and maintain privileged access to the computer by circumventing normal authentication and authorization mechanisms.
And here is the most scary part about Rootkits:
Rootkit detection is difficult because a rootkit may be able to subvert the software that is intended to find it. Detection methods include using an alternate, trusted operating system, behavioral-based methods, signature scanning, difference scanning, and memory dump analysis.
Removal can be complicated or practically impossible, especially in cases where the rootkit resides in the kernel. Reinstallation of the operating system may be the only alternative.
Of course, there are some rootkit scanners that help detect rootkits.
What is a Virus?
This is the most popularly used term by security software, but probably also the least understood one. A computer virus is a computer program that can copy itself and infect a computer. A true virus can spread from one computer to another (in some form of executable code) when its host is taken to the target computer; for instance because a user sent it over a network, the Internet or carried it on a removable medium such as a floppy disk, CD, DVD or USB drive.
The most important part of above definition is “can copy itself.” This is what separates a virus from other type of malware listed above. And this is the feature that makes it most dangerous: Viruses can easily spread themselves to multiple computers. A single virus infection in a corporate network can cause havoc with the entire network. Do make sure you always have a good antivirus program.
What is a Trojan Horse?
This is a less commonly used term, but the software that it represents is equally dangerous. A Trojan horse, or Trojan, is malware that appears to perform a desirable function for the user to run or install but instead facilitates unauthorized access of the user’s computer system. It is a harmful piece of software that looks legitimate. Users are typically tricked into loading and executing it on their systems.
What is a Worm?
The definition of Worm looks too similar to that of a Virus, but the definition also points out differences between both:
A computer worm is a self-replicating malware computer program. It uses a computer network to send copies of itself to other nodes (computers on the network) and it may do so without any user intervention. This is due to security shortcomings on the target computer. Unlike a virus, it does not need to attach itself to an existing program. Worms almost always cause at least some
harm to the network, even if only by consuming bandwidth, whereas viruses almost always corrupt or modify files on a targeted computer.
Polymorphic malware :
To avoid detection, polymorphic malware constantly changes it’s own code, often using encryption with a variable key. This stealthy technique poses a problem for typical scanners.
There is one other catagory that some consider undesirable on their computers and most antivirus services will identify them. These programs are known as PUPS, short for Potentially Unwanted Programs, and include such things as keyloggers, ad supported programs, etc.
Keyloggers are programs that record each keystroke on a computer. PUPS are programs that can be used for good reasons or bad reasons. Since antivirus services have no way of knowing how the PUP is being used, it detects and warns of the existing PUP.