When you surf the Internet, this is the software that displays, plays or downloads advertising onto your computer. It’s a cousin of spyware. Adware is an annoyance more than a security risk, but it may run without your knowledge and also may track and relay information about your Web browsing habits without your consent.

A type of data scrambling -- or encryption -- that makes information unintelligible to unauthorized users. Asymmetric encryption deploys two sets of keys (keys are pieces of information that control an algorithm). One is a widely-known public key that encodes messages. The other key is private so that only the recipient can ultimately unscramble the data.

An extra copy of a computer file kept away from the original in case of a computer meltdown. Backup is essential to recover files in case the original is lost or damaged.

An attack on your computer that combines several different attack modes, such as a worm, a Trojan horse, and a keylogger -- all rolled into one. Needless to say, to defend against such an attack, you must have a combination of security tools and protection layers.

The word is derived from the term Web log. This is a Web site where a person displays journal entries or commentary about news, politics, food or other topics on an ongoing basis. Some bloggers also let others post entries on their blog.

Named after 10th century Danish King Harald Blatan (Bluetooth), who was known as a uniter, these are wireless standards that allow for short-range communication between different devices. Bluetooth enables PDAs, mobile phones, laptops, printers, game consoles, and other electronic devices to connect and exchange data. However, security flaws can expose Bluetooth-enabled devices to attack.

Jargon for a group of computers that have been compromised and brought under the control of a person to launch attacks, send spam or conduct other malicious acts.

Derived from the word robot, a bot is an automated software program that performs or simulates human actions on the Internet. Bots are used for legitimate purposes by search engines and Instant Messaging (IM) programs. They can also be used nefariously to take control of computers, launch attacks, and compromise data. 

Software programs on your computer that make it easy to explore the World Wide Web. Browsers translate encoded files into the images, sounds, text and other elements you view on the Internet. Popular browsers include Microsoft’s Internet Explorer, Mozilla’s Firefox, Safari and Opera.

A trusted third party -- often a technology company -- that holds the public “keys” to code-scrambling technologies, also known as encryption. The certificate authority issues digital certificates to validate that a public key belongs to a certain person or entity. A second key to the code, the private key, is used by the recipient to crack the code and decipher the information.

An online forum in which people communicate with each other by exchanging typed messages in real time. Some chat rooms use moderators to monitor behavior and stop any disruptive or unruly conduct.  

A group of two or more computers linked by cables or wireless signals or both, which can communicate with one another using network protocols. Networks can also include other devices, including printers, routers, and network hubs.

A small file placed on your computer when you visit a Web page. Cookies remember you and your preferences when you revisit that page, facilitating virtual shopping carts, page customization, and targeted advertising. They can also be used to track your movements through cyberspace, which some consider a violation of privacy. But they can’t read your hard drive or damage your computer.

The science of using mathematical equations to protect the contents of digital data. Cryptography keeps digital information confidential through encryption, authentication or by controlling access. It’s already used in ATM cards, online shopping and creating computer passwords.

Reducing a data file’s size by encoding its contents. Compression is used to maximize storage space on a computer and speed transmission of a file over the Internet. Compressed files are often placed in an archive file and must be extracted and decompressed before use; others are used in a compressed state. Common compression archive formats include .zip, .sit, .tar, .jar, and .cab.  

A physical reorganization of data on your computer hard drive. The pieces of each file are put closer together and placed in a more logical order. This makes hard drives operate faster and have more storage space.

In certain types of code scrambling, or encryption, a digital certificate validates that a public “key” to the code is owned by the entity sending the scrambled data. Digital certificates are issued by a certificate authority. They contain the public key as well as verification that the certificate is authentic and comes from the sender.

A special code that’s attached to digitally transmitted messages to verify the sender’s identity. Similar to a handwritten signature, the idea is to guarantee that the person sending the transmission is really who he/she claims. These are widely used in electronic commerce.

An Internet address for a Web site. For example, the domain name coca-cola is the address for The Coca Cola Company’s Web site. Every domain name also has a suffix, or top level domain, such as .com, .gov or .org.

Manipulation of the domain name system to redirect traffic from a legitimate Web address to an imposter Web site. Used to perpetrate phishing and other types of malicious attacks by sending users to the phony Web site without warning.

Stands for Denial-of-Service: a malicious attack designed to flood a computer or network with useless traffic in order to render it unusable by clients. The attack is perpetrated by unleashing malicious code that simply shuts down resources.

To copy data, a file, image or other material and save it to a diskette, CD or onto your computer hard drive.

The scrambling of data into a secret code. Encryption is a security method which makes information unreadable to anyone who doesn’t have a “key” to decipher the data. It’s commonly used to secure online purchases and other transactions.

A compilation of data that is stored on a computer under a unique name. Files are stored in hierarchies under folders, directories or catalogs. 

File Transfer Protocol: a set of communication rules for transferring files between computers over the Internet. FTP works in a similar way to HTTP, which enables the transfer of Web pages to a user’s browser. 

GIF stands for Graphics Interchange Format. GIFs are an image file format popular on the Internet because they can be compressed without losing image quality. However, as GIFs are limited to 256 colors, they are unsuitable for digital photos but fine for illustrations.

HTTP rules for passing information to a server that’s secured using encryption and/or authentication measures. The Web site addresses offering secure HTTP connections begin with https://.

Slang for a person with exceptional programming skills and technical knowledge. The term has commonly come to stand for someone who gains unauthorized access to computer systems for malicious or criminal purposes. In the programming community, however, such persons are termed “crackers” and the label “hacker” is a complimentary term referring to well-respected, skilled programmers.  

Hypertext Markup Language: the standard computer language used to create and format Web pages. Controls the layout, design, and display of text, hyperlinks, images, and other media on most Web pages. 

The standard code used in HTML to signal a hyperlink or format change. These tags are usually bracketed by < and >.

Hypertext Transfer Protocol: the communication rules for controlling how Web browsers and servers pass information back and forth over the Internet. Web site addresses begin with http://, but most Web browsers default to the http protocol -- meaning you don’t have to type that code before the www.whatever.com you are looking for on the Web. 

A clickable word, phrase, or image that takes you from one Web page to another Web page on the Internet. Hyperlinks are created using HTML tags, and when displayed in a browser, they’re typically underlined or visually distinct with a color.

Short for Instant Message, a program that allows two or more people to communicate with one another over the Internet in real time. While most IM exchanges are in text, some IM programs also offer streaming audio-visual conferencing and voice. IM can also refer to messages sent by instant messaging, or to the act of sending an instant message.

This is when the size of an image file is reduced, while maintaining acceptable visual quality. Used extensively on the Web, JPEG and GIF are common compressed image file formats. 

A public, worldwide network connecting millions of computers and computer networks. The World Wide Web, email, instant messaging, chat rooms, and many other online services and data transmissions are facilitated by the Internet.

Internet Protocol address, a unique identifier for each computer or other device on a network, including the Internet. The concept is similar to a phone number. IP addresses consist of a string of numbers that allow computers, routers, printers, and other devices to recognize one another and communicate.

This is short for Joint Photographic Experts Group, a popular compressed file format for digital photos. JPEGs are favored on the Web because they can be compressed while maintaining high resolution. Many digital cameras create JPEGs by default when you download images onto your computer. The file extension for JPEGs is .jpg or .jpeg.

A type of surveillance software that monitors and captures every keystroke a user types into a computer keyboard. They can record email, Web browsing, instant messages and any other information you type. Sometimes used by employers to make sure employees are using work computers for business. But increasingly embedded into spyware and used to gather passwords, user names, and other private information for nefarious purposes.

Malicious software designed to disrupt or damage computer systems or data. Includes viruses, worms, Trojan horses, and some keyloggers, spyware, adware and bots. While some malware is circulated simply to disrupt activities, increasingly criminals are using these programs to invade privacy, steal information, or infiltrate computers without permission. 

Stands for mpeg audio layer 3, a compressed audio file format, popular for playing sound and music recordings over handheld and desktop audio players, such as the iPod.

A security method requiring both parties to confirm a transaction to prove their identities. On the Web, this would require both a consumer’s Web browser and a business’ Web server to prove their identities to one another, thus ensuring both the seller and buyer are legitimate. Used on financial and commerce sites, mutual authentication can help prevent phishing and other kinds of fraud. 

A hardware or software device, (or combination of the two), that prevents unauthorized Internet users from gaining access to private networks.  

Hardware that connects computers to one another on a local network.

Short for Personal Digital Assistant, a handheld device combining computing applications, Internet, mobile phone, address books and other features. Many PDAs connect to the Web, send email, and synchronize with home computers; some work as cellular phones.

Software installed on an end-user’s personal computer that controls access and communications to and from the computer and the Internet or a local network. Blocks hackers and other unauthorized traffic, while allowing authorized traffic through.

An attempt to obtain personal or private information (most often financial-related) from Internet surfers by hijacking a Web site’s domain name, or URL, and redirecting users to an imposter Web site. At the Web site, fraudulent requests for private information are made.

The sending of email or instant messages intended to mislead people into divulging confidential information, such as passwords and bank account numbers. Typically routes unsuspecting users to phony Web sites to make fraudulent requests for information. 

A podcast is a regularly updated set of mp3 audio files available for download from the Internet. 

In data scrambling, or encryption, an unpublished key used to decipher messages encoded using a corresponding public key.

In data scrambling, or encryption, a key made available to anyone who wants to send a coded message to the owner of the key. The owner of the public key uses his or her private key to unscramble messages.

A data-scrambling technique using public keys to encrypt messages, digital signatures to validate the integrity of messages, and digital certificates to authenticate the identity of public key owners.

A set of standards and services designed to support data-scrambling using public key cryptography. PKI uses digital certificates issued by certificate authorities to authenticate public keys and the entities that own them.

Using backup files to restore original data that has been damaged or lost by a computer crash, failure, virus or other mishap. 

A hardware device that connects at least two networks, such as an organization’s local area network and the Internet. The router directs traffic from one network to the appropriate destination on the other. Some routers have network firewalls and other features built into them.

RSS stands for Really Simple Syndication: a way for an Internet user to get feeds of content from news sites, blogs and other Web sites with fast-changing information. Look for a tiny orange rectangle with the initials RSS on Web sites. By clicking on the box, you can sign up for an RSS feed from a Web site and get updated information automatically sent to your Web browser, email or a designated Web page.

Simple Mail Transfer Protocol: the de facto standard for sending email messages over the Internet.

The practice of deceiving users into divulging private information. A social engineer often uses the telephone or Internet to convince trusting individuals to turn over information so that it can be stolen for scams. Often associated with phishing, pharming, spam, and other Internet-based cons.

Unsolicited email, usually sent in bulk to a large number of random accounts. Spam often contains ads for products or services, including pornography and counterfeit medicines. Also used in phishing scams and other online fraud. The amount of spam can be minimized using software that filters out email from known spammers. 

This is spam sent to your Instant Messaging (IM) account. Spim is usually sent in bulk to a large number of IM accounts at once and often contains ads and links to product Web pages. It may also be used in phishing scams or to spread malware.

Spam over Internet telephony. These are unsolicited phone calls to people who use Voice over Internet Protocol (VoIP), a way to place calls through your computer connection. 

A type of software that monitors what you do on your computer and then relays that information to someone else over the Internet. Some programs track what kind of Web sites you visit and the results are shared with advertising agencies. Other kinds of spyware tracks what you type in an attempt to capture credit card numbers or passwords.  

A code-scrambling -- or encryption -- method that uses the same secret key (a piece of information that controls a secret algorithm) to scramble and unscramble messages. 

Named after the giant hollow wooden horse of Trojan War myth, this is a malicious program disguised as legitimate software. It sometimes gives a perpetrator the power to take remote control of your computer. It also may attack data or systems. 

Uniform Resource Locator: a Web site or Web page’s address (for example: CNN or CNN-Sports). Browsers use URLs to identify and download Web pages from the Web servers where they’re located so that you get to the right page on the Web.

A phony Web site that poses as a legitimate site. URL spoofing is an attempt to masquerade or closely mimic the Web address displayed in a Web browser’s address bar. It’s used in phishing attacks and other online scams to make an imposter Web site seem legitimate. Sometimes the fake site’s URL is spelled similar to the spoofed site.

A self-replicating computer program that infects files, programs, and computer systems. Some computer viruses are malicious and can damage data, computers and systems.

Voice over Internet Protocol: telephone conversations that takes place over the Internet instead of land-based telephone networks. Some services are free, others charge for more reliable connections that are more like traditional phone calling.

A program for personal computers used to navigate the Internet. Web browsers primarily use a computer language called Hypertext Transfer Protocol to communicate, hence most Web addresses begin with “http.”

A program that automatically browses the Web. Many legitimate Web sites, including search engines, deploy Web crawlers to download a vast number of Web sites, which are then indexed to make searches more efficient. Crawlers can also be used to do Web site maintenance or to harvest email addresses for spam purposes.

A digital page, accessible via the Internet, that contains text, images, video or audio. A Web page is one of often many pages that are combined to create a Web site.

Wireless fidelity, a play on the term hi-fidelity, refers to wireless networks, devices, or anything associated with 802.11 wireless technology. The Wi-Fi standard for wireless network communication is developed by the Institute of Electrical and Electronics Engineers (IEEE). There are several versions, or modulations, of 802.11.  802.11b and 802.11g are among the most popular. 

A public space where you can connect to the Internet by using a wireless-enabled device such as a laptop.  Some Wi-Fi hotspots have no security measures in place, while others secure transmission standards.

An interactive graphic component that a computer user can interact with, like a button, check box, window, or text box. 

A global information-sharing service available over the Internet. The Web is made up of a worldwide collection of computers, or Web servers, which make text documents, pictures, audio, video and other types of information available to the public. 

The name was adapted from “The Shockwave Rider,” a science fiction novel. Worm has come to refer to a malicious program that can copy and propagate itself over the Internet using email programs or other transport tools. A worm may also compromise the security of an infected computer or cause system and data damage.

Stands for Wi-Fi Protected Access. WPA is part of the 802.11 IEEE wireless standards. It’s an extension and improvement of the WEP security protocol, offering better scrambling of data and user authentication measures. The Wi-Fi standard for wireless network communication is developed by the Institute of Electrical and Electronics Engineers (IEEE). There are several versions, or modulations, of 802.11.  802.11b and 802.11g are among the most popular.

WPA2 enhances the WPA security protocol in the 802.11 IEEE wireless standards. WEP, WPA, and WPA2 are all still in use, but WPA and WPA2 offer better protection. The Wi-Fi standard for wireless network communication is developed by the Institute of Electrical and Electronics Engineers (IEEE). There are several versions, or modulations, of 802.11.  802.11b and 802.11g are among the most popular.

Stands for Extensible Markup language. XML is a computer language that Web programmers use to format text and other information so it can be shared on the Web. Unlike HTML, another markup language, it does not have a fixed set of formatting tags. Instead, it is a language that gives programmers the flexibility to create their own markup tags so that they can organize and present information in innovative ways.