Virus, Trojans, Worms, Malware and Spyware

They Affect us all. But do you know what they are?

WHAT IS A COMPUTER VIRUS

Source: From Wikipedia, the free encyclopedia

A computer virus is a computer program that can copy itself and infect a computer without the permission or knowledge of the user. The term "virus" is also commonly but erroneously used to refer to other types of malware, adware and spyware programs that do not have the reproductive ability. A true virus can only spread from one computer to another when its host (some form of executable code) is taken to the target computer, for instance because a user sent it over a network or the Internet, or carried it on a removable medium such as a floppy disk, CD, or USB drive. Viruses can increase their chances of spreading to other computers by infecting files on a network file system or a file system that is accessed by another computer.

Viruses are sometimes confused with computer worms and Trojan horses, which are technically different. A worm can spread itself to other computers without needing to be transferred as part of a host, and a Trojan horse is a program that appears harmless but has a hidden agenda. Worms and Trojans, like viruses, may cause harm to either a computer system's hosted data, functional performance, or networking throughput, when they are executed. Some viruses and other malware have symptoms noticeable to the computer user, but most are surreptitious. This makes it hard for the average user to notice, find and disable and is why specialist anti-virus programs are now commonplace.

Most personal computers are now connected to the Internet and to local area networks, facilitating the spread of malicious code. Today's viruses may also take advantage of network services such as the World Wide Web, e-mail, Instant Messaging and file sharing systems to spread, blurring the line between viruses and worms. Furthermore, some sources use an alternative terminology in which a virus is any form of self-replicating malware.

WHAT IS A COMPUTER TROJAN

Source: From Wikipedia, the free encyclopedia

In the context of computing and software, a Trojan horse, also known as a trojan, is a form of malware that appears to perform a desirable function but in fact performs undisclosed malicious functions that allow unauthorized access to the host machine. As such, a computer worm or virus may also be classed as a Trojan horse if they display these characteristics.

The term is derived from the classical story of the Trojan Horse.

Trojan horse payloads are almost always designed to cause harm, but can also be harmless. They are classified based on how they breach and damage systems. The six main types of Trojan horse payloads are:

* Remote Accessing
* Data Destruction
* Downloader
* Server Trojan(Proxy, FTP , IRC, Email, HTTP/HTTPS, etc.)
* Security software disabler
* Denial-of-service attack (DoS)

Some examples of damage are:

* Erasing or overwriting data on a computer
* Re-installing itself after being disabled
* Encrypting files in a cryptoviral extortion attack
* Corrupting files in a subtle way
* Upload and download of files
* Copying fake links, which lead to false websites, chats, or other account based websites, showing any local account name on the computer falsely engaging in untrue context
* Falsifying records of downloading software, movies, or games from websites never visited by the victim.
* Allowing remote access to the victim's computer. This is called a RAT (remote access trojan)
* Spreading other malware, such as viruses (this type of trojan horse is called a 'dropper' or 'vector')
* Setting up networks of zombie computers in order to launch DDoS attacks or send spam.
* Spying on the user of a computer and covertly reporting data like browsing habits to other people (see the article on spyware)
* Making screenshots
* Logging keystrokes to steal information such as passwords and credit card numbers
* Phishing for bank or other account details, which can be used for criminal activities
* Installing a backdoor on a computer system
* Opening and closing CD-ROM tray
* Playing sounds, videos or displaying images
* Calling using the modem to expensive numbers, thus causing massive phone bills
* Harvesting e-mail addresses and using them for spam
* Restarting the computer whenever the infected program is started
* Deactivating or interfering with anti-virus and firewall programs
* Deactivating or interfering with other competing forms of malware
* Randomly shutting off the computer
* Installing a virus
* Slowing down your computer
* Displaying pornographic sites

WHAT IS A COMPUTER WORM

Source: From Wikipedia, the free encyclopedia

A computer worm is a self-replicating computer program. It uses a network to send copies of itself to other nodes (computers on the network) and it may do so without any user intervention. 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, if only by consuming bandwidth, whereas viruses almost always corrupt or modify files on a targeted computer.

Many worms that have been created are only designed to spread, and don't attempt to alter the systems they pass through. However, as the Morris worm and Mydoom showed, the network traffic and other unintended effects can often cause major disruption. A "payload" is code designed to do more than spread the worm - it might delete files on a host system (e.g., the ExploreZip worm), encrypt files in a cryptoviral extortion attack, or send documents via e-mail. A very common payload for worms is to install a backdoor in the infected computer to allow the creation of a "zombie" under control of the worm author - Sobig and Mydoom are examples which created zombies. Networks of such machines are often referred to as botnets and are very commonly used by spam senders for sending junk email or to cloak their website's address. Spammers are therefore thought to be a source of funding for the creation of such worms,and worm writers have been caught selling lists of IP addresses of infected machines. Others try to blackmail companies with threatened DoS attacks.

Backdoors can be exploited by other malware, including worms. Examples include Doomjuice, which spreads better using the backdoor opened by Mydoom, and at least one instance of malware taking advantage of the rootkit and backdoor installed by the Sony/BMG DRM software utilized by millions of music CDs prior to late 2005.

Beginning with the very first research into worms at Xerox PARC there have been attempts to create useful worms. The Nachi family of worms, for example, tried to download and install patches from Microsoft's website to fix vulnerabilities in the host system — by exploiting those same vulnerabilities. In practice, although this may have made these systems more secure, it generated considerable network traffic, rebooted the machine in the course of patching it, and did its work without the consent of the computer's owner or user.

Other worms, such as XSS worms have been written for research to determine the factors of how worms spread, such as social activity and change in user behavior.

Still, more worms do very little, or are pranks, such as one that sends the popular image macro of an owl with the phrase "O RLY?" to a print queue in the infected computer.

Most security experts regard all worms as malware, whatever their payload or their writers' intentions.

WHAT IS SPYWARE

Source: From Wikipedia, the free encyclopedia

Spyware is computer software that is installed surreptitiously on a personal computer to intercept or take partial control over the user's interaction with the computer, without the user's informed consent.

While the term spyware suggests software that secretly monitors the user's behavior, 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, but can also interfere with user control of the computer in other ways, such as installing additional software, and redirecting Web browser activity. Spyware is known to change computer settings, resulting in slow connection speeds, different home pages, and/or loss of Internet or functionality of other programs. In an attempt to increase the understanding of spyware, a more formal classification of its included software types is captured under the term privacy-invasive software.

In response to the emergence of spyware, a small industry has sprung up dealing in anti-spyware software. Running anti-spyware software has become a widely recognized element of computer security best practices for Microsoft Windows desktop computers. A number of jurisdictions have passed anti-spyware laws, which usually target any software that is surreptitiously installed to control a user's computer. The US Federal Trade Commission has placed on the Internet a page of advice to consumers about how to lower the risk of spyware infection, including a list of "dos" and "don'ts."

The first recorded use of the term spyware occurred on October 16, 1995 in a Usenet post that poked fun at Microsoft's business model. Spyware at first denoted hardware meant for espionage purposes. However, in early 2000 the founder of Zone Labs, Gregor Freund, used the term in a press release for the ZoneAlarm Personal Firewall. Since then, "spyware" has taken on its present sense. According to a 2005 study by AOL and the National Cyber-Security Alliance, 61 percent of surveyed users' computers had some form of spyware. 92 percent of surveyed users with spyware reported that they did not know of its presence, and 91 percent reported that they had not given permission for the installation of the spyware. As of 2006, spyware has become one of the preeminent security threats to computer systems running Microsoft Windows operating systems. Computers where Internet Explorer (IE) is the primary browser are particularly vulnerable to such attacks not only because IE is the most widely-used, but because its tight integration with Windows allows spyware access to crucial parts of the operating system.

Before Internet Explorer 7 was released, the browser would automatically display an installation window for any ActiveX component that a website wanted to install. The combination of user naiveté towards malware and the assumption by Internet Explorer that all ActiveX components are benign, led, in part, to the massive spread of spyware. Many spyware components would also make use of exploits in Javascript, Internet Explorer and Windows to install without user knowledge or permission.

The Windows Registry contains multiple sections that by modifying keys values allows software to be executed automatically when the operating system boots. Spyware can exploit this design to circumvent attempts at removal. The spyware typically will link itself from each location in the registry that allows execution. Once running, the spyware will periodically check if any of these links are removed. If so, they will be automatically restored. This ensures that the spyware will execute when the operating system is booted even if some (or most) of the registry links are removed.