Malware, short for malicious software, (sometimes referred to as pestware[1]) is a software designed to harm or secretly access a computer system without the owner's informed consent. The expression is a general term used by computer professionals to mean a variety of forms of hostile, intrusive, or annoying software or program code.[2]
Software is considered to be malware based on the perceived intent of the creator rather than any particular features. Malware includes computer viruses, worms, trojan horses, spyware, dishonest adware, scareware,crimeware, most rootkits, and other malicious and unwanted software or program. In law, malware is sometimes known as a computer contaminant, for instance in the legal codes of several U.S. states, including California andWest Virginia.[3][4]
Preliminary results from Symantec published in 2008 suggested that "the release rate of malicious code and other unwanted programs may be exceeding that of legitimate software applications."[5] According to F-Secure, "As much malware [was] produced in 2007 as in the previous 20 years altogether."[6] Malware's most common pathway from criminals to users is through the Internet: primarily by e-mail and the World Wide Web.[7]
The prevalence of malware as a vehicle for organized Internet crime, along with the general inability of traditional anti-malware protection platforms (products) to protect against the continuous stream of unique and newly produced malware, has seen the adoption of a new mindset for businesses operating on the Internet: the acknowledgment that some sizable percentage of Internet customers will always be infected for some reason or another, and that they need to continue doing business with infected customers. The result is a greater emphasis on back-office systems designed to spot fraudulent activities associated with advanced malware operating on customers' computers.[8]
On March 29, 2010, Symantec Corporation named Shaoxing, China, as the world's malware capital.[9]
Malware is not the same as defective software, that is, software that has a legitimate purpose but contains harmful bugs. Sometimes, malware is disguised as genuine software, and may come from an official site. Therefore, some security programs, such as McAfee may call malware "potentially unwanted programs" or "PUP". Though a computer virus is malware that can reproduce itself, the term is often used erroneously to refer to the entire category.
Many early infectious programs, including the first Internet Worm and a number of MS-DOS viruses, were written as experiments or pranks. They were generally intended to be harmless or merely annoying, rather than to cause serious damage to computer systems. In some cases, the perpetrator did not realize how much harm his or her creations would do. Young programmers learning about viruses and their techniques wrote them simply for practice, or to see how far they could spread. As late as 1999, widespread viruses such as the Melissa virus and the David virus appear to have been written chiefly as pranks. The first mobile phone virus, Cabir, appeared in 2004.
Hostile intent related to vandalism can be found in programs designed to cause harm or data loss. Many DOS viruses, and the Windows ExploreZip worm, were designed to destroy files on a hard disk, or to corrupt the file system by writing invalid data to them. Network-borne worms such as the 2001 Code Red worm or the Ramen worm fall into the same category. Designed to vandalize web pages, worms may seem like the online equivalent to graffiti tagging, with the author's alias or affinity group appearing everywhere the worm goes.[citation needed]
Since the rise of widespread broadband Internet access, malicious software has been designed for a profit, for examples forced advertising. For instance, since 2003, the majority of widespread viruses and worms have been designed to take control of users' computers for black-market exploitation.[10] Infected "zombie computers" are used to send email spam, to host contraband data such as child pornography [11], or to engage in distributed denial-of-serviceattacks as a form of extortion.[12]
Another strictly for-profit category of malware has emerged in spyware -- programs designed to monitor users' web browsing, display unsolicited advertisements, or redirect affiliate marketing revenues to the spyware creator. Spyware programs do not spread like viruses; they are, in general, installed by exploiting security holes or are packaged with user-installed software, such as peer-to-peer applications.
The best-known types of malware, viruses and worms, are known for the manner in which they spread, rather than any other particular behavior. The termcomputer virus is used for a program that has infected some executable software and, when run, causes the virus to spread to other executables. Viruses may also contain a payload that performs other actions, often malicious. On the other hand, a worm is a program that actively transmits itself over a network to infect other computers. It too may carry a payload.
These definitions lead to the observation that a virus requires user intervention to spread, whereas a worm spreads itself automatically. Using this distinction, infections transmitted by email or Microsoft Word documents, which rely on the recipient opening a file or email to infect the system, would be classified as viruses rather than worms.
Some writers in the trade and popular press misunderstand this distinction and use the terms interchangeably.
Before Internet access became widespread, viruses spread on personal computers by infecting the executable boot sectors of floppy disks. By inserting a copy of itself into the machine code instructions in these executables, a virus causes itself to be run whenever a program is run or the disk is booted. Early computer viruses were written for the Apple II and Macintosh, but they became more widespread with the dominance of the IBM PC and MS-DOS system. Executable-infecting viruses are dependent on users exchanging software or boot-able floppies, so they spread rapidly in computer hobbyist circles.
The first worms, network-borne infectious programs, originated not on personal computers, but on multitasking Unix systems. The first well-known worm was the Internet Worm of 1988, which infected SunOS and VAX BSD systems. Unlike a virus, this worm did not insert itself into other programs. Instead, it exploited security holes (vulnerabilities) in network server programs and started itself running as a separate process. This same behaviour is used by today's worms as well.
With the rise of the Microsoft Windows platform in the 1990s, and the flexible macros of its applications, it became possible to write infectious code in the macro language of Microsoft Word and similar programs. These macro viruses infect documents and templates rather than applications (executables), but rely on the fact that macros in a Word document are a form of executable code.
Today, worms are most commonly written for the Windows OS, although a few like Mare-D[13] and the Lion worm[14] are also written for Linux and Unixsystems. Worms today work in the same basic way as 1988's Internet Worm: they scan the network and leverage vulnerable computers to replicate. Because they need no human intervention, worms can spread with incredible speed. The SQL Slammer infected thousands of computers in a few minutes.[15]
For a malicious program to accomplish its goals, it must be able to run without being shut down, or deleted by the user or administrator of the computer system on which it is running. Concealment can also help get the malware installed in the first place. When a malicious program is disguised as something innocuous or desirable, users may be tempted to install it without knowing what it does. This is the technique of the Trojan horse or trojan.
In broad terms, a Trojan horse is any program that invites the user to run it, concealing a harmful or malicious payload. The payload may take effect immediately and can lead to many undesirable effects, such as deleting the user's files or further installing malicious or undesirable software. Trojan horses known as droppers are used to start off a worm outbreak, by injecting the worm into users' local networks.
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. Spyware authors who attempt to act in a legal fashion may include an end-user license agreement that states the behavior of the spyware in loose terms, which the users are unlikely to read or understand.
Once a malicious program is installed on a system, it is essential that it stays concealed, to avoid detection and disinfection. The same is true when a human attacker breaks into a computer directly. Techniques known as rootkits allow this concealment, by modifying the host's 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, allowing the attacker to gain administrator (root) access. Today, the term is used more generally for concealment routines in a malicious program.
Some malicious programs contain routines to defend against removal, not merely to hide themselves, but to repel attempts to remove them. An early example of this behavior is recorded in the Jargon File tale of a pair of programs infesting a Xerox CP-V time sharing system:
Similar techniques are used by some modern malware, wherein the malware starts a number of processes that monitor and restore one another as needed. In the event a user running Microsoft Windows is infected with such malware, if they wish to manually stop it, they could use Task Manager's 'processes' tab to find the main process (the one that spawned the "resurrector process(es)"), and use the 'end process tree' function, which would kill not only the main process, but the "resurrector(s)" as well, since they were started by the main process. Some malware programs use other techniques, such as naming the infected file similar to a legitimate or trustworthy file (expl0rer.exe VS explorer.exe).
A backdoor is a method of bypassing normal authentication procedures. Once a system has been compromised (by one of the above methods, or in some other way), one or more backdoors may be installed in order to allow easier access in the future. Backdoors may also be installed prior to malicious software, to allow attackers entry.
The idea has often been suggested that computer manufacturers preinstall backdoors on their systems to provide technical support for customers, but this has never been reliably verified. Crackers typically use backdoors to secure remote access to a computer, while attempting to remain hidden from casual inspection. To install backdoors crackers may use Trojan horses, worms, or other methods.
During the 1980s and 1990s, it was usually taken for granted that malicious programs were created as a form of vandalism or prank. More recently, the greater share of malware programs have been written with a profit motive (financial or otherwise) in mind. This can be taken as the malware authors' choice to monetize their control over infected systems: to turn that control into a source of revenue.
Spyware programs are commercially produced for the purpose of gathering information about computer users, showing them pop-up ads, or altering web-browser behavior for the financial benefit of the spyware creator. For instance, some spyware programs redirect search engine results to paid advertisements. Others, often called "stealware" by the media, overwrite affiliate marketing codes so that revenue is redirected to the spyware creator rather than the intended recipient.
Spyware programs are sometimes installed as Trojan horses of one sort or another. They differ in that their creators present themselves openly as businesses, for instance by selling advertising space on the pop-ups created by the malware. Most such programs present the user with an end-user license agreement that purportedly protects the creator from prosecution under computer contaminant laws. However, spyware EULAs have not yet been upheld in court.
Another way that financially motivated malware creators can profit from their infections is to directly use the infected computers to do work for the creator. The infected computers are used as proxies to send out spam messages. A computer left in this state is often known as a zombie computer. The advantage to spammers of using infected computers is they provide anonymity, protecting the spammer from prosecution. Spammers have also used infected PCs to target anti-spam organizations with distributed denial-of-service attacks.
In order to coordinate the activity of many infected computers, attackers have used coordinating systems known as botnets. In a botnet, the malware ormalbot logs in to an Internet Relay Chat channel or other chat system. The attacker can then give instructions to all the infected systems simultaneously. Botnets can also be used to push upgraded malware to the infected systems, keeping them resistant to antivirus software or other security measures.
It is possible for a malware creator to profit by stealing sensitive information from a victim. Some malware programs install a key logger, which intercepts the user's keystrokes when entering a password, credit card number, or other information that may be exploited. This is then transmitted to the malware creator automatically, enabling credit card fraud and other theft. Similarly, malware may copy the CD key or password for online games, allowing the creator to steal accounts or virtual items.
Another way of stealing money from the infected PC owner is to take control of a dial-up modem and dial an expensive toll call. Dialer (or porn dialer) software dials up a premium-rate telephone number such as a U.S. "900 number" and leave the line open, charging the toll to the infected user.
Data-stealing malware is a web threat that divests victims of personal and proprietary information with the intent of monetizing stolen data through direct use or underground distribution. Content security threats that fall under this umbrella include keyloggers, screen scrapers, spyware, adware, backdoors, andbots. The term does not refer to activities such as spam, phishing, DNS poisoning, SEO abuse, etc. However, when these threats result in file download or direct installation, as most hybrid attacks do, files that act as agents to proxy information will fall into the data-stealing malware category.
Does not leave traces of the event
Frequently changes and extends its functions
Thwarts Intrusion Detection Systems (IDS) after successful installation
Thwarts disk encryption
Thwarts Data Loss Prevention (DLP)
There is a group of software (Alexa toolbar, Google toolbar, Eclipse data usage collector, etc) that send data to a central server about which pages have been visited or which features of the software have been used. However differently from "classic" malware these tools document activities and only send data with the user's approval. The user may opt in to share the data in exchange to the additional features and services, or (in case of Eclipse) as the form of voluntary support for the project. Some security tools report such loggers as malware while others do not. The status of the group is questionable. Some tools like PDFCreator are more on the boundary than others because opting out has been made more complex than it could be (during the installation, the user needs to uncheck two check boxes rather than one). However also PDFCreator is only sometimes mentioned as malware and is still subject of discussions.
In this context, as throughout, it should be borne in mind that the “system” under attack may be of various types, e.g. a single computer and operating system, a network or an application.
Various factors make a system more vulnerable to malware:
An oft-cited cause of vulnerability of networks is homogeneity or software monoculture.[21] For example, Microsoft Windows or Apple Mac have such a large share of the market that concentrating on either could enable a cracker to subvert a large number of systems, but any total monoculture is a problem. Instead, introducing inhomogeneity (diversity), purely for the sake of robustness, could increase short-term costs for training and maintenance. However, having a few diverse nodes would deter total shutdown of the network, and allow those nodes to help with recovery of the infected nodes. Such separate, functional redundancy would avoid the cost of a total shutdown, would avoid homogeneity as the problem of "all eggs in one basket".
Most systems contain bugs, or loopholes, which may be exploited by malware. A typical example is the buffer-overrun weakness, in which an interface designed to store data, in a small area of memory, allows the caller to supply more data than will fit. This extra data then overwrites the interface's own executable structure (past the end of the buffer and other data). In this manner, malware can force the system to execute malicious code, by replacing legitimate code with its own payload of instructions (or data values) copied into live memory, outside the buffer area.
Originally, PCs had to be booted from floppy disks, and until recently it was common for this to be the default boot device. This meant that a corrupt floppy disk could subvert the computer during booting, and the same applies to CDs. Although that is now less common, it is still possible to forget that one has changed the default, and rare that a BIOS makes one confirm a boot from removable media.
In some systems, non-administrator users are over-privileged by design, in the sense that they are allowed to modify internal structures of the system. In some environments, users are over-privileged because they have been inappropriately granted administrator or equivalent status. This is primarily a configuration decision, but on Microsoft Windows systems the default configuration is to over-privilege the user. This situation exists due to decisions made by Microsoft to prioritize compatibility with older systems above security configuration in newer systems[citation needed] and because typical applications were developed without the under-privileged users in mind. As privilege escalation exploits have increased this priority is shifting for the release of MicrosoftWindows Vista. As a result, many existing applications that require excess privilege (over-privileged code) may have compatibility problems with Vista. However, Vista's User Account Control feature attempts to remedy applications not designed for under-privileged users, acting as a crutch to resolve the privileged access problem inherent in legacy applications.
Malware, running as over-privileged code, can use this privilege to subvert the system. Almost all currently popular operating systems, and also many scripting applications allow code too many privileges, usually in the sense that when a user executes code, the system allows that code all rights of that user. This makes users vulnerable to malware in the form of e-mail attachments, which may or may not be disguised.
Given this state of affairs, users are warned only to open attachments they trust, and to be wary of code received from untrusted sources. It is also common for operating systems to be designed so that device drivers need escalated privileges, while they are supplied by more and more hardware manufacturers.
Over-privileged code dates from the time when most programs were either delivered with a computer or written in-house, and repairing it would at a stroke render most antivirus software almost redundant. It would, however, have appreciable consequences for the user interface and system management.
The system would have to maintain privilege profiles, and know which to apply for each user and program. In the case of newly installed software, an administrator would need to set up default profiles for the new code.
Eliminating vulnerability to rogue device drivers is probably harder than for arbitrary rogue executables. Two techniques, used in VMS, that can help are memory mapping only the registers of the device in question and a system interface associating the driver with interrupts from the device.
Other approaches are:
Such approaches, however, if not fully integrated with the operating system, would reduplicate effort and not be universally applied, both of which would be detrimental to security.
As malware attacks become more frequent, attention has begun to shift from viruses and spyware protection, to malware protection, and programs have been developed to specifically combat them.
Anti-malware programs can combat malware in two ways:
Real-time protection from malware works identically to real-time antivirus protection: the software scans disk files at download time, and blocks the activity of components known to represent malware. In some cases, it may also intercept attempts to install start-up items or to modify browser settings. Because many malware components are installed as a result of browser exploits or user error, using security software (some of which are anti-malware, though many are not) to "sandbox" browsers (essentially babysit the user and their browser) can also be effective in helping to restrict any damage done.
The notion of a self-reproducing computer program can be traced back to when presented lectures that encompassed the theory and organization of complicated automata.[22] Neumann showed that in theory a program could reproduce itself. This constituted a plausibility result in computability theory. Fred Cohen experimented with computer viruses and confirmed Neumann's postulate. He also investigated other properties of malware (detectability, self-obfuscating programs that used rudimentary encryption that he called "evolutionary", and so on). His 1988 doctoral dissertation was on the subject of computer viruses.[23] Cohen's faculty advisor, Leonard Adleman (the A in RSA) presented a rigorous proof that, in the general case, algorithmically determining whether a virus is or is not present is Turing undecidable.[24] This problem must not be mistaken for that of determining, within a broad class of programs, that a virus is not present; this problem differs in that it does not require the ability to recognize all viruses. Adleman's proof is perhaps the deepest result in malware computability theory to date and it relies on Cantor's diagonal argument as well as the halting problem. Ironically, it was later shown by Young and Yung that Adleman's work in cryptography is ideal in constructing a virus that is highly resistant to reverse-engineering by presenting the notion of a cryptovirus.[25] A cryptovirus is a virus that contains and uses a public key and randomly generated symmetric cipher initialization vector(IV) and session key (SK). In the cryptoviral extortion attack, the virus hybrid encrypts plaintext data on the victim's machine using the randomly generated IV and SK. The IV+SK are then encrypted using the virus writer's public key. In theory the victim must negotiate with the virus writer to get the IV+SK back in order to decrypt the ciphertext (assuming there are no backups). Analysis of the virus reveals the public key, not the IV and SK needed for decryption, or the private key needed to recover the IV and SK. This result was the first to show that computational complexity theory can be used to devise malware that is robust against reverse-engineering.
Another growing area of computer virus research is to mathematically model the infection behavior of worms using models such as Lotka–Volterra equations, which has been applied in the study of biological virus. Various virus propagation scenarios have been studied by researchers such as propagation of computer virus, fighting virus with virus like predator codes,[26][27] effectiveness of patching etc.
Grayware[28] (or Greynet) is a general term sometimes used as a classification for applications that behave in a manner that is annoying or undesirable, and yet less serious or troublesome than malware.[29] Grayware encompasses spyware, adware, dialers, joke programs, remote access tools, and any other unwelcome files and programs apart from viruses that are designed to harm the performance of computers on your network. The term has been in use since at least as early as September 2004.[30]
Grayware refers to applications or files that are not classified as viruses or trojan horse programs, but can still negatively affect the performance of the computers on your network and introduce significant security risks to your organization.[31] Often grayware performs a variety of undesired actions such as irritating users with pop-up windows, tracking user habits and unnecessarily exposing computer vulnerabilities to attack.
Published by NationalTechExpress.com - An IT Consulting firm located in Miami, Florida, serving residents and small business owners in Miami, Pinecrest, Coconut Grove, Coral Gables, South Miami, Palmetto Bay, Kendall with effective computer repair, PC & MAC, network & systems administration, and more computer technical support services. To schedule a FREE consultation, call 305-254-5050 or contact us now »