Computer virus is a computer program that can copy itself and infect a computer without permission or knowledge of the user. The original virus may modify the copies or the copies may modify themselves, as occurs in a metamorphic virus. A virus can only spread from one computer to another when its host is taken to the uninfected computer, for instance by a user sending it over a network or the Internet, or by carrying it on a removable medium such as a floppy disk, CD, or USB drive. Additionally, viruses can spread 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. A worm can spread itself to other computers without needing to be transferred as part of a host, and a Trojan horse is a file that appears harmless until executed.

Many 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, 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.

Some viruses are programmed to damage the computer by damaging programs, deleting files, or reformatting the hard disk. Others are not designed to do any damage, but simply replicate themselves and perhaps make their presence known by presenting text, video, or audio messages. Even these benign viruses can create problems for the computer user. They typically take up computer memory used by legitimate programs. As a result, they often cause erratic behavior and can result in system crashes. In addition, many viruses are bug-ridden, and these bugs may lead to system crashes and data loss.

But the goodnews is, you can actually prevent such infection by installing antivirus programs in your computer and have updated virus definition.

You can find many good antivirus programs in the market and installation is easy.

PC World magazine has highlighted some top antivirus performer.

Take a look at this review:

1. Kaspersky antivirus 6

8. Trend Micro Antivirus Plus Antispyware 2007

The facts about MALWARE

Malware is software designed to infiltrate or damage a computer system without the owner's infomed consent. It is a portmanteau of the words "malicious" and "software". 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.

Many normal computer users are however still unfamiliar with the term, and most never use it. Instead, "computer virus" is used in common parlance and often in the general media to describe all kinds of malware, though not all malware is a virus. Another term that has been recently coined for malware is badware, perhaps due to the anti-malware initiative Stopbadware or corruption of the term "malware".

Software is considered malware based on the perceived intent of the creator rather than any particular features. It includes computer viruses, worms, trojan horses, spyware, dishonest adware, and other malicious and unwanted software. In law, malware is sometimes known as a computer contaminant, for instance in the legal codes of California, West Virginia, and several other U.S. states.

Malware should not be confused with defective software, that is, software which has a legitimate purpose but contains harmful bugs.

The facts about TROJANS

In the context of computer software, a Trojan horse is a program that installs malicious software while under the guise of doing something else. Though not limited in their payload, Trojan horses are more notorious for installing backdoor programs which allow unauthorized non permissible remote access to the victim's machine by unwanted parties - normally with malicious intentions. Unlike a computer virus, a Trojan horse does not propagate by inserting its code into other computer files. The term is derived from the classical myth of the Trojan Horse. Like the mythical Trojan Horse, the malicious code is hidden in a computer program or other computer file which may appear to be useful, interesting, or at the very least harmless to an unsuspecting user. When this computer program or file is executed by the unsuspecting user, the malicious code is also executed resulting in the set up or installation of the malicious Trojan horse program.

Often the term is shortened to simply Trojan.

There are two common types of Trojan horses. One is ordinary software that has been corrupted by a hacker. A hacker inserts malicious code into the program that executes while the program is used or modified. Examples include various implementations of weather alerting programs, computer clock setting software, and peer-to-peer file sharing utilities. The other type of Trojan is a standalone program that masquerades as something else, like a game or image file, in order to trick the user into executing the file or program.

Trojan horse programs cannot operate autonomously, in contrast to some other types of malware, like viruses or worms. Trojan horse programs depend on actions by the intended victims. As such, if Trojans replicate and distribute themselves, each new victim must run the Trojan.

In the field of computer architecture, 'Trojan Horse' can also refer to security loopholes that allow kernel code to access anything for which it is not authorized.

The facts about WORM

A computer worm is a self-replicating computer program. It uses a network to send copies of itself to other nodes (computer terminals 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 always harm the network (if only by consuming bandwidth), whereas viruses always infect or corrupt files on a targeted computer.

The facts about ADWARE

Adware or advertising-supported software is any software package which automatically plays, displays, or downloads advertising material to a computer after the software is installed on it or while the application is being used.

The facts about PHISHING

In computing, phishing is an attempt to criminally and fraudulently acquire sensitive information, such as usernames, passwords and credit card details, by masquerading as a trustworthy entity in an electronic communication. eBay, PayPal and online banks are common targets. Phishing is typically carried out by email or instant messaging, and often directs users to enter details at a website, although phone contact has also been used. Phishing is an example of social engineering techniques used to fool users. Attempts to deal with the growing number of reported phishing incidents include legislation, user training, public awareness, and technical measures.

The first recorded mention of the term phishing is on the alt.online-service.America-online Usenet newsgroup on January 2, 1996, although the term may have appeared earlier in the print edition of the hacker magazine 2600. A phishing technique was described in detail as early as 1987, in a paper and presentation delivered to the International HP Users Group, Interex. The term phishing is a variant of fishing, probably influenced by phreaking, and alludes to the use of increasingly sophisticated baits used in the hope of a "catch" of financial information and passwords. The word may also be linked to leetspeak, in which ph is a common substitution for f.The popular theory that it is a portmanteau of password harvesting is an example of folk etymology.

The facts about KEYLOGGER

Keystroke logging (often called keylogging) is a diagnostic tool used in software development that captures the user's keystrokes. It can be useful to determine sources of error in computer systems and is sometimes used to measure employee productivity on certain clerical tasks.

Such systems are also highly useful for law enforcement and espionage—for instance, providing a means to obtain passwords or encryption keys and thus bypassing other security measures. However, keyloggers are widely available on the Internet and can be used by private parties to spy on the computer usage of others.

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, but can also interfere with user control of the computer in other ways, such as installing additional software, redirecting Web browser activity, or diverting advertising revenue to a third party. 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.

History and development

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% of surveyed users' computers had some form of spyware. 92% of surveyed users with spyware reported that they did not know of its presence, and 91% 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. In an estimate based on customer-sent scan logs, Webroot Software, makers of Spy Sweeper, said that 9 out of 10 computers connected to the Internet are infected. 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 flaws in Javascript, Internet Explorer and Windows to install without user knowledge or permission.

The registry also contains numerous locations that allow software to be executed automatically when the operating system boots. Spyware often exploits this design to help it circumvent attempts at removal. The spyware typically will link itself from each of 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.

Spyware, adware and tracking:

The term adware frequently refers to any software which displays advertisements, whether or not the user has consented. Programs such as the Eudora mail client display advertisements as an alternative to shareware registration fees. These classify as "adware" in the sense of advertising-supported software, but not as spyware. Adware in this form does not operate surreptitiously or mislead the user, and provides the user with a specific service.

Although most adware is spyware in a different sense for a different reason: it displays advertisements related to what it finds from spying on you. Claria Corporation's Gator Software and Exact Advertising's BargainBuddy are examples. Visited Web sites frequently install Gator on client machines in a surreptitious manner, and it directs revenue to the installing site and to Claria by displaying advertisements to the user. The user receives many pop-up advertisements.

Other spyware behavior, such as reporting on websites the user visits, occurs in the background. The data is used for "targeted" advertisement impressions. The prevalence of spyware has cast suspicion upon other programs that track Web browsing, even for statistical or research purposes. Some observers describe the Alexa Toolbar, an Internet Explorer plug-in published by Amazon.com, as spyware, and some anti-spyware programs such as AdAware report it as such. Many of these adware distributing companies are backed by millions of dollars of adware-generating revenues. Adware and spyware are similar to viruses in that they can be malicious in nature, however, people are now profitting from these threats making them more and more popular.

Similarly, software bundled with free, advertising-supported programs such as P2P act as spyware, (and if removed disable the 'parent' program) yet people are willing to download it. This presents a dilemma for proprietors of anti-spyware products whose removal tools may inadvertently disable wanted programs. For example, recent test results show that bundled software (WhenUSave) is ignored by popular anti spyware program AdAware, (but removed as spyware by most scanners) because it is part of the popular (but recently decommissioned) Edonkey client. To address this dilemma, the Anti-Spyware Coalition has been working on building consensus within the anti-spyware industry as to what is and isn't acceptable software behavior. To accomplish their goal, this group of anti-spyware companies, academics, and consumer groups have collectively published a series of documents including a definition of spyware, risk model, and best practices document.

Spyware, virus and worm:

Unlike viruses and worms, spyware does not usually self-replicate. Like many recent viruses, however, spyware — by design — exploits infected computers for commercial gain. Typical tactics furthering this goal include delivery of unsolicited pop-up advertisements; theft of personal information (including financial information such as credit card numbers); monitoring of Web-browsing activity for marketing purposes; or routing of HTTP requests to advertising sites.

Routes of infection:

Spyware does not directly spread in the manner of a computer virus or worm: generally, an infected system does not attempt to transmit the infection to other computers. Instead, spyware gets on a system through deception of the user or through exploitation of software vulnerabilities.

Most spyware is installed without users' knowledge. Since they tend not to install software if they know that it will disrupt their working environment and compromise their privacy, spyware deceives users, either by piggybacking on a piece of desirable software such as Kazaa, or tricking them into installing it (the Trojan horse method). Some "rogue" anti-spyware programs masquerade as security software, while being spyware themselves.

The distributor of spyware usually presents the program as a useful utility — for instance as a "Web accelerator" or as a helpful software agent. Users download and install the software without immediately suspecting that it could cause harm. For example, Bonzi Buddy, a spyware program targeted at children, claims that:

He will explore the Internet with you as your very own friend and sidekick! He can talk, walk, joke, browse, search, e-mail, and download like no other friend you've ever had! He even has the ability to compare prices on the products you love and help you save money! Best of all, he's FREE!

Spyware can also come bundled with shareware or other downloadable software, as well as music CDs. The user downloads a program and installs it, and the installer additionally installs the spyware. Although the desirable software itself may do no harm, the bundled spyware does. In some cases, spyware authors have paid shareware authors to bundle spyware with their software. In other cases, spyware authors have repackaged desirable free software with installers that add spyware.

A third way of distributing spyware involves tricking users by manipulating security features designed to prevent unwanted installations. Internet Explorer prevents websites from initiating an unwanted download. Instead, it requires a user action, such as clicking on a link. However, links can prove deceptive: for instance, a pop-up ad may appear like a standard Windows dialog box. The box contains a message such as "Would you like to optimize your Internet access?" with links which look like buttons reading Yes and No. No matter which "button" the user presses, a download starts, placing the spyware on the user's system. Later versions of Internet Explorer offer fewer avenues for this attack.

Some spyware authors infect a system through security holes in the Web browser or in other software. When the user navigates to a Web page controlled by the spyware author, the page contains code which attacks the browser and forces the download and installation of spyware. The spyware author would also have some extensive knowledge of commercially-available anti-virus and firewall software. This has become known as a "drive-by download", which leaves the user a hapless bystander to the attack. Common browser exploits target security vulnerabilities in Internet Explorer and in the Sun Microsystems Java runtime.

The installation of spyware frequently involves Internet Explorer. Its popularity and history of security issues have made it the most frequent target. Its deep integration with the Windows environment and scriptability make it an obvious point of attack into Windows. Internet Explorer also serves as a point of attachment for spyware in the form of Browser Helper Objects, which modify the browser's behaviour to add toolbars or to redirect traffic.

In a few cases, a worm or virus has delivered a spyware payload. Some attackers used the Spybot worm to install spyware that put pornographic pop-ups on the infected system's screen.By directing traffic to ads set up to channel funds to the spyware authors, they profit personally.

A spyware program is rarely alone on a computer: an affected machine can rapidly be infected by many other components. Users frequently notice unwanted behavior and degradation of system performance. A spyware infestation can create significant unwanted CPU activity, disk usage, and network traffic, all of which slow the computer down. Stability issues, such as application or system-wide crashes, are also common. Spyware which interferes with networking software commonly causes difficulty connecting to the Internet.

In some infections, the spyware is not even evident. Users assume in those situations that the issues relate to hardware, to Windows installation problems, or a virus. Some owners of badly infected systems resort to contacting technical support experts, or even buying a new computer because the existing system "has become too slow". Badly infected systems may require a clean reinstallation of all their software in order to return to full functionality.

Only rarely does a single piece of software render a computer unusable. Rather, a computer is likely to have multiple infections. As the 2004 AOL study noted, if a computer has any spyware at all, it typically has dozens of different pieces installed. The cumulative effect, and the interactions between spyware components, cause the symptoms commonly reported by users: a computer which slows to a crawl, overwhelmed by the many parasitic processes running on it. Moreover, some types of spyware disable software firewalls and anti-virus software, and/or reduce browser security settings, thus opening the system to further opportunistic infections, much like an immune deficiency disease. Some spyware has disabled or even removed competing spyware programs, on the grounds that more spyware-related annoyances make it even more likely that users will take action to remove the programs. One spyware maker, Avenue Media, even sued a competitor, Direct Revenue, over this; the two later settled with an agreement not to disable each others' products.

Some other types of spyware (Targetsoft, for example) modify system files so they will be harder to remove. Targetsoft modifies the "Winsock" Windows Sockets files. The deletion of the spyware-infected file "inetadpt.dll" will interrupt normal networking usage. Unlike users of many other operating systems, a typical Windows user has administrative privileges, mostly for convenience. Because of this, any program the user runs (intentionally or not) has unrestricted access to the system too. Spyware, along with other threats, has led some Windows users to move to other platforms such as Linux or Apple Macintosh, which are less attractive targets for malware. This is because these programs are not granted unrestricted access to the operating system by default, though some allege it's mainly due to the far smaller number of machines installed with these operating systems making spyware development potentially less profitable for these platforms. As with other operating systems, Windows users too are able to follow the principle of least privilege and use non-administrator least user access accounts, or to reduce the privileges of specific vulnerable Internet-facing proceses such as Internet Explorer (through the use of tools such as DropMyRights). However as this is not a default configuration, few users do this.

Advertisements:

Many spyware programs display advertisements. Some programs simply display pop-up ads on a regular basis; for instance, one every several minutes, or one when the user opens a new browser window. Others display ads in response to specific sites that the user visits. Spyware operators present this feature as desirable to advertisers, who may buy ad placement in pop-ups displayed when the user visits a particular site. It is also one of the purposes for which spyware programs gather information on user behavior. Pop-ups are one of users' most common complaints about spyware.

Many users complain about irritating or offensive advertisements as well. As with many banner ads, many spyware advertisements use animation or flickering banners which can be visually distracting and annoying to users. Pop-up ads for pornography often display indiscriminately. Links to these sites may be added to the browser window, history or search function. When children are the users, this could possibly violate anti-pornography laws in some jurisdictions.

A further issue in the case of some spyware programs has to do with the replacement of banner ads on viewed web sites. Spyware that acts as a web proxy or a Browser Helper Object can replace references to a site's own advertisements (which fund the site) with advertisements that instead fund the spyware operator. This cuts into the margins of advertising-funded Web sites.

"Stealware" and affiliate fraud:

A few spyware vendors, notably 180 Solutions, have written what the New York Times has dubbed "stealware", and what spyware-researcher Ben Edelman terms affiliate fraud, a form of click fraud. Stealware diverts the payment of affiliate marketing revenues from the legitimate affiliate to the spyware vendor.

Spyware which attacks affiliate networks places the spyware operator's affiliate tag on the user's activity—replacing any other tag, if there is one. The spyware operator is the only party that gains from this. The user has their choices thwarted, a legitimate affiliate loses revenue, networks' reputations are injured, and vendors are harmed by having to pay out affiliate revenues to an "affiliate" who is not party to a contract.

Affiliate fraud is a violation of the terms of service of most affiliate marketing networks. As a result, spyware operators such as 180 Solutions have been terminated from affiliate networks including LinkShare and ShareSale.

Identity theft and fraud:

In one case, spyware has been closely associated with identity theft. In August 2005, researchers from security software firm Sunbelt Software believed that the makers of the common CoolWebSearch spyware had used it to transmit "chat sessions, user names, passwords, bank information, etc.", but it turned out that "it actually (was) its own sophisticated criminal little trojan that's independent of CWS." This case is currently under investigation by the FBI.

The Federal Trade Commission estimates that 27.3 million Americans have been victims of identity theft, and that financial losses from identity theft totaled nearly $48 billion for businesses and financial institutions and at least $5 billion in out-of-pocket expenses for individuals.

Spyware-makers may commit wire fraud with dialer program spyware. These can reset a modem to dial up a premium-rate telephone number instead of the usual ISP. Connecting to these suspicious numbers involves long-distance or overseas charges which invariably result in high call costs. Dialers are ineffective on computers that do not have a modem, or are not connected to a telephone line.

Digital rights management:

Some copy-protection technologies have borrowed from spyware. In 2005, Sony BMG Music Entertainment was found to be using rootkits in its XC digital rights management technology, Like spyware, not only was it difficult to detect and uninstall, it was so poorly written that most efforts to remove it could have rendered computers unable to function. Texas state attorney general Greg Abbott filed suit, and three separate class-action suits were filed. Sony BMG later provided a workaround on its website to help users remove it.

Beginning in April 25, 2006, Microsoft's Windows Genuine Advantage Notifications application installed on most Windows PCs as a "critical security update". While the main purpose of this deliberately non-uninstallable application is making sure the copy of Windows on the machine was lawfully purchased and installed, it also installs software that has been accused of "phoning home" on a daily basis, like spyware. It can be removed with the RemoveWGA tool.

Spyware and cookies:

Anti-spyware programs often report Web advertisers' HTTP cookies, the small text files that track browsing activity, as spyware. While they are not always inherently malicious, many users object to third parties using space on their personal computers for their business purposes, and so many anti-spyware programs offer to remove them.

Examples of spyware

These common spyware programs illustrate the diversity of behaviors found in these attacks. Note that as with computer viruses, researchers give names to spyware programs which may not be used by their creators. Programs may be grouped into "families" based not on shared program code, but on common behaviors, or by "following the money" of apparent financial or business connections. For instance, a number of the spyware programs distributed by Claria are collectively known as "Gator". Likewise, programs which are frequently installed together may be described as parts of the same spyware package, even if they function separately.

• CoolWebSearch, a group of programs, takes advantage of Internet Explorer vulnerabilities. The package directs traffic to advertisements on Web sites including coolwebsearch.com. It displays pop-up ads, rewrites search engine results, and alters the infected computer's hosts file to direct DNS lookups to these sites.

• Internet Optimizer, also known as DyFuCa, redirects Internet Explorer error pages to advertising. When users follow a broken link or enter an erroneous URL, they see a page of advertisements. However, because password-protected Web sites (HTTP Basic authentication) use the same mechanism as HTTP errors, Internet Optimizer makes it impossible for the user to access password-protected sites.

• Zango (formerly 180 Solutions) transmits detailed information to advertisers about the Web sites which users visit. It also alters HTTP requests for affiliate advertisements linked from a Web site, so that the advertisements make unearned profit for the 180 Solutions company. It opens pop-up ads that cover over the Web sites of competing companies.

• HuntBar, aka WinTools or Adware.Websearch, was installed by an ActiveX drive-by download at affiliate Web sites, or by advertisements displayed by other spyware programs — an example of how spyware can install more spyware. These programs add toolbars to IE, track aggregate browsing behavior, redirect affiliate references, and display advertisements.

• Movieland, also known as Moviepass.tv or Popcorn.net, is a movie download service that has been the subject of thousands of complaints to the Federal Trade Commission (FTC), the Washington State Attorney General's Office, the Better Business Bureau, and others by consumers claiming they were held hostage by its repeated pop-up windows and demands for payment. The FTC has filed a complaint against Movieland.com and eleven other defendants (list), charging them with having "engaged in a nationwide scheme to use deception and coercion to extract payments from consumers." The complaint alleges that the software repeatedly opened oversized pop-up windows that could not be closed or minimized, accompanied by music that lasted nearly a minute, demanding payment of at least $29.95 to end the pop-up cycle; and claiming that consumers had signed up for a three-day free trial but did not cancel their membership before the trial period was over, and were thus obligated to pay.

Legal issues related to spyware:

Criminal law:

Unauthorized access to a computer is illegal under computer crime laws, such as the U.S. Computer Fraud and Abuse Act, the U.K.'s Computer Misuse Act and similar laws in other countries. Since the owners of computers infected with spyware generally claim that they never authorized the installation, a prima facie reading would suggest that the promulgation of spyware would count as a criminal act. Law enforcement has often pursued the authors of other malware, particularly viruses. However, few spyware developers have been prosecuted, and many operate openly as strictly legitimate businesses, though some have faced lawsuits.

Spyware producers argue that, contrary to the users' claims, users do in fact give consent to installations. Spyware that comes bundled with shareware applications may be described in the legalese text of an end-user license agreement (EULA). Many users habitually ignore these purported contracts, but spyware companies such as Claria claim these demonstrate that users have consented.

Despite the ubiquity of EULAs and of "clickwrap" agreements, under which a single click can be taken as consent to the entire text, relatively little case law has resulted from their use. It has been established in most common law jurisdictions that a clickwrap agreement can be a binding contract in certain circumstances. This does not, however, mean that every such agreement is a contract or that every term in one is enforceable.

Some jurisdictions, including the U.S. states of Iowa and Washington, have passed laws criminalizing some forms of spyware. Such laws make it illegal for anyone other than the owner or operator of a computer to install software that alters Web-browser settings, monitors keystrokes, or disables computer-security software.

In the United States, lawmakers introduced a bill in 2005 entitled the Internet Spyware Prevention Act, which would imprison creators of spyware.

Civil law

Former New York State Attorney General and now current Governor Eliot Spitzer has pursued spyware companies for fraudulent installation of software.^] In a suit brought in 2005 by Spitzer, the California firm Intermix Media, Inc. ended up settling by agreeing to pay US$7.5 million and to stop distributing spyware.

The hijacking of Web advertisements has also led to litigation. In June 2002, a number of large Web publishers sued Claria for replacing advertisements, but settled out of court.

Courts have not yet had to decide whether advertisers can be held liable for spyware which displays their ads. In many cases, the companies whose advertisements appear in spyware pop-ups do not directly do business with the spyware firm. Rather, they have contracted with an advertising agency, which in turn contracts with an online subcontractor who gets paid by the number of "impressions" or appearances of the advertisement. Some major firms such as Dell Computer and Mercedes-Benz have sacked advertising agencies which have run their ads in spyware.

Libel suits by spyware developers

Litigation has gone both ways. Since "spyware" has become a common pejorative, some makers have filed libel and defamation actions when their products have been so described. In 2003, Gator (now known as Claria) filed suit against the website PC Pitstop for describing its program as "spyware". PC Pitstop settled, agreeing not to use the word "spyware", but continues to describe harm caused by the Gator/Claria software. As a result, other antispyware and antivirus companies have also used other terms such as "potentially unwanted programs" or greyware to denote these products.

Remedies and prevention:

As the spyware threat has worsened, a number of techniques have emerged to counteract it. These include programs designed to remove or to block spyware, as well as various user practices which reduce the chance of getting spyware on a system.

Nonetheless, spyware remains a costly problem. When a large number of pieces of spyware have infected a Windows computer, the only remedy may involve backing up user data, and fully reinstalling the operating system.

Anti-spyware programs:

Many programmers and some commercial firms have released products designed to remove or block spyware. Steve Gibson's OptOut, mentioned above, pioneered a growing category. Programs such as Lavasoft's Ad-Aware SE and Patrick Kolla's Spybot - Search & Destroy rapidly gained popularity as effective tools to remove, and in some cases intercept, spyware programs. More recently Microsoft acquired the GIANT AntiSpyware software, rebranding it as Windows AntiSpyware beta and releasing it as a free download for Genuine Windows XP and Windows 2003 users. In early spring, 2006, Microsoft renamed the beta software to Windows Defender, and it was released as a free download in October 2006. Microsoft currently ships the product for free with Windows Vista. Other well-known anti-spyware products include:

• 	PC Tools's Spyware Doctor		Sunbelt Software's Counterspy
  	Trend Micro's HijackThis		Webroot Software's Spy Sweeper
  	ParetoLogic's Anti-SpywareXoftSpy SE

Major anti-virus firms such as Symantec, McAfee and Sophos have come later to the table, adding anti-spyware features to their existing anti-virus products. Early on, anti-virus firms expressed reluctance to add anti-spyware functions, citing lawsuits brought by spyware authors against the authors of web sites and programs which described their products as "spyware". However, recent versions of these major firms' home and business anti-virus products do include anti-spyware functions, albeit treated differently from viruses. Symantec Anti-Virus, for instance, categorizes spyware programs as "extended threats" and now offers real-time protection from them (as it does for viruses). Recently, the anti-virus company Grisoft, creator of AVG Anti-Virus, acquired anti-spyware firm Ewido Networks, re-labeling their Ewido anti-spyware program as AVG Anti-Spyware. This shows a trend by anti virus companies to launch a dedicated solution to spyware and malware. Zone Labs, creator of Zone Alarm firewall have also released an anti spyware program.

Anti-spyware programs can combat spyware in two ways:

1. They can provide real time protection against the installation of spyware software on your computer. This type of spyware protection works the same way as that of anti-virus protection in that the anti-spyware software scans all incoming network data for spyware software and blocks any threats it comes across.

2. Anti-spyware software programs can be used solely for detection and removal of spyware software that has already been installed onto your computer. This type of spyware protection is normally much easier to use and more popular. With this spyware protection software you can schedule weekly, daily, or monthly scans of your computer to detect and remove any spyware software that has been installed on your computer. This type of anti-spyware software scans the contents of the windows registry, operating system files, and installed programs on your computer and will provide a list of any threats found, allowing you to choose what you want to delete and what you want to keep.

Such programs inspect the contents of the Windows registry, the operating system files, and installed programs, and remove files and entries which match a list of known spyware components. Real-time protection from spyware works identically to real-time anti-virus protection: the software scans disk files at download time, and blocks the activity of components known to represent spyware. In some cases, it may also intercept attempts to install start-up items or to modify browser settings. Because many spyware and adware are installed as a result of browser exploits or user error, using security software (some of which are antispyware, though many are not) to sandbox browsers can also be effective to help restrict any damage done.

Earlier versions of anti-spyware programs focused chiefly on detection and removal. Javacool Software's SpywareBlaster, one of the first to offer real-time protection, blocked the installation of ActiveX-based and other spyware programs.

Like most anti-virus software, many anti-spyware/adware tools require a frequently-updated database of threats. As new spyware programs are released, anti-spyware developers discover and evaluate them, making "signatures" or "definitions" which allow the software to detect and remove the spyware. As a result, anti-spyware software is of limited usefulness without a regular source of updates. Some vendors provide a subscription-based update service, while others provide updates free. Updates may be installed automatically on a schedule or before doing a scan, or may be done manually.

Not all programs rely on updated definitions. Some programs rely partly (for instance many antispyware programs such as Windows Defender, Spybot's TeaTimer and Spysweeper) or fully (programs falling under the class of Hips such as BillP's WinPatrol), on historical observation. They watch certain configuration parameters (such as certain portions of the Windows registry or browser configuration) and report any change to the user, without judgment or recommendation. While they do not rely on updated definitions, which may allow them to spot newer spyware, they can offer no guidance. The user is left to determine "what did I just do, and is this configuration change appropriate?"

Windows Defender's Spynet attempts to alleviate this through offering a community to share information, which helps guide both users, who can look at decisions made by others, and analysts, who can spot fast-spreading spyware. A popular generic spyware removal tool used by those with a certain degree of expertise is HijackThis, which scans certain areas of the Windows OS where spyware often resides and presents a list with items to delete manually. As most of the items are legitimate windows files/registry entries it is advised for those who are less knowledgeable on this subject to post a HijackThis log on the numerous antispyware sites and let the experts decide what to delete.

If a spyware program is not blocked and manages to get itself installed, it may resist attempts to terminate or uninstall it. Some programs work in pairs: when an anti-spyware scanner (or the user) terminates one running process, the other one respawns the killed program. Likewise, some spyware will detect attempts to remove registry keys and immediately add them again. Usually, booting the infected computer in safe mode allows an anti-spyware program a better chance of removing persistent spyware. Killing the process tree can also work.

A new breed of spyware (Look2Me spyware by NicTechNetworks is a good example) is starting to hide inside system-critical processes and start up even in safe mode. With no process to terminate they are harder to detect and remove. Sometimes they do not even leave any on-disk signatures. Rootkit technology is also seeing increasing use^] as is the use of NTFS alternate data streams. Newer spyware programs also have specific countermeasures against well known anti-malware products and may prevent them from running or being installed, or even uninstall them. An example of one that uses all three methods is Gromozon, a new breed of malware. It uses alternate data streams to hide. A rootkit hides it even from alternate data streams scanners and actively stops popular rootkit scanners from running.

Fake anti-spyware programs:

Malicious programmers have released a large number of fake anti-spyware programs, and widely distributed Web banner ads now spuriously warn users that their computers have been infected with spyware, directing them to purchase programs which do not actually remove spyware — or worse, may add more spyware of their own.

The recent proliferation of fake or spoofed antivirus products has occasioned some concern. Such products often bill themselves as antispyware, antivirus, or registry cleaners, and sometimes feature popups prompting users to install them. They are called rogue software.

Known offenders include:

• errorsafe (AKA system doctor)
• Pest Trap
• SpyAxe
• AntiVirus Gold
• SpywareStrike
• Spyware Quake
• WorldAntiSpy
• Spylocked
• SpyShredder
• SysProtect
• Spy Sheriff
• Spy Wiper
• PAL Spyware Remover
• PSGuard
• Malware
• WinAntiVirus Pro 2006
• WinFixer
• Spydawn
• ContraVirus
• UltimateCleaner
• MagicAntiSpy
• AV System Care
• Registrycleanerxp.com
• SecurePCcleaner
• PCSecuresystem

On 2006-01-26, Microsoft and the Washington state attorney general filed suit against Secure Computer for its Spyware Cleaner product. On 2006-12-04, the Washington attorney general announced that Secure Computer had paid $1 million to settle with the state. As of that date, Microsoft's case against Secure Computer remained pending.

Security practices:

To deter spyware, computer users have found several practices useful in addition to installing anti-spyware programs.

Many system operators install a web browser other than IE, such as Avant or Opera or Mozilla Firefox. Although these have also suffered some security vulnerabilities, their comparatively small market share compared to Internet Explorer makes it uneconomic for hackers to target users on those browsers.Though no browser is completely safe, Internet Explorer is at a greater risk for spyware infection due to its large user base as well as vulnerabilities such as ActiveX.

Some ISPs — particularly colleges and universities — have taken a different approach to blocking spyware: they use their network firewalls and web proxies to block access to Web sites known to install spyware. On March 31, 2005, Cornell University's Information Technology department released a report detailing the behavior of one particular piece of proxy-based spyware, Marketscore, and the steps the university took to intercept it. Many other educational institutions have taken similar steps. Spyware programs which redirect network traffic cause greater technical-support problems than programs which merely display ads or monitor users' behavior, and so may more readily attract institutional attention.

Some users install a large hosts file which prevents the user's computer from connecting to known spyware related web addresses. However, by connecting to the numeric IP address, rather than the domain name, spyware may bypass this sort of protection.

Spyware may get installed via certain shareware programs offered for download. Downloading programs only from reputable sources can provide some protection from this source of attack. Recently, CNet revamped its download directory: it has stated that it will only keep files that pass inspection by Ad-Aware and Spyware Doctor.

Notable programs distributed with spyware

• Bonzi Buddy
• Dope Wars
• ErrorGuard
• Grokster
• Kazaa
• Morpheus
• RadLight
• WeatherBug
• EDonkey2000
• Sony's Extended Copy Protection involved the installation of spyware from audio compact discs through autorun. This practice sparked considerable controversy when it was discovered.
• WildTangent. The antispyware program CounterSpy used to say that it's okay to keep WildTangent, but it now says that the spyware Winpipe is "possibly distributed with the adware bundler WildTangent or from a threat included in that bundler"

Notable programs formerly distributed with spyware:

• AOL Instant Messenger (AOL Instant Messenger still packages Viewpoint Media Player, and WildTangent)
• DivX (except for the paid version, and the "standard" version without the encoder). DivX announced removal of GAIN software from version 5.2.
• FlashGet (trial version prior to program being made freeware)