An attack combining a number of traditional attack methods, like a worm, a Trojan horse, and a keylogger. Most require a combination of security tools and protection layers to defend.

Named after 10th century Danish King, Harald Blatand (Bluetooth), who was known as a uniter: a conventional set of wireless standards for short-range communication between wireless headsets, phones, PDAs, keyboards, and other disparate devices. Bluetooth supports a number of security measures, but it has flaws which can expose Bluetooth-enabled devices to attack.

A "bot" is a type of malware that allows an attacker to take control over an affected computer. Also known as "Web robots", bots are usually part of a network of infected machines, known as a "botnet", which is typically made up of victim machines that stretch across the globe.

A group of computers which have been compromised and brought under the control of an individual; the individual uses malware installed on the compromised computers to launch denial-of-service attacks, send spam, or perpetrate other malicious acts.

In public key cryptography, a trusted third party who authenticates entities and their public keys. To do so, certificate authorities issue digital certificates, which validate that a public key belongs to the person whose digital signature is listed on the certificate.

An online forum where groups can exchange comments in real time. Many chat rooms use moderators to monitor behavior and control access. However, chat room users can join anonymously, and sexual predators have used that anonymity to disguise themselves and target unsuspecting children and teens.

A small text file placed on your computer when you visit a web page. Used to remember you and your preferences when you revisit that page or to track your browsing activities, cookies facilitate virtual shopping carts, page customization, and targeted advertising. They are not programs and cannot read your hard drive or cause damage to your computer.

Cybercrime is motivated by fraud, typified by the bogus emails sent by "phishers" that aim to steal personal information. The tools driving their attacks and fueling the blackmarket are crimeware - bots, Trojan horses, and spyware.

Process of reorganizing information on your hard drive by placing parts of files in a more logical order and in closer proximity to one another. Fragmentation can slow down your computer; when defragmented, drives are faster and have larger areas of free space.

Also called public key certificate or identity certificate: In public key cryptography, validates that a public key is owned by the entity sending encrypted or digitally signed data with that key. Digital certificates are issued by a certificate authority and contain the sender’s public key plus a digital signature verifying that the certificate is authentic and that the key belongs to the sender.

Used in public key cryptography to validate the integrity of encrypted data and to confirm both the identity of a digital certificate holder and the authenticity of the certificate itself.

Denial-of-Service: an attack on a computer or network in which bandwidth is flooded or resources are overloaded to the point where the computer or network's services are unavailable to clients. Can also be carried out by malicious code that simply shuts down resources.

Email Spam is the electronic version of junk mail. It involves sending unwanted messages, often unsolicited advertising, to a large number of recipients. Spam is a serious security concern as it can be used to deliver Trojan horses, viruses, worms, spyware, and targeted phishing attacks.

A method of scrambling or encoding data to prevent unauthorized users from reading or tampering with the data. Only individuals with access to a password or key can decrypt and use the data. The data can include messages, files, folders, or disks.

Software that controls access and communications between a computer and the Internet or a local network. Blocks hackers and other unauthorized traffic, while allowing authorized traffic through.

File Transfer Protocol: a conventional set of communication rules for transferring files between computers on the Internet. While most Web browsers can transfer files using FTP, you can also use a dedicated FTP program, which usually provides better security features.

Graphics Interchange Format: an image file format popular on the Internet. GIFs are favored for graphics because they can be compressed without losing image quality. However, GIFs are limited to 256 colors and are therefore unsuitable for digital photos. See also, JPEG.

Commonly, a person who uses programming skills and technical knowledge to gain unauthorized access to computer systems for malicious or criminal purposes. The programming community, however, prefers to use the term cracker for such persons; they reserve hacker for any well-respected, highly skilled programmer.

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

Reducing the size of an image file, while maintaining an acceptable level of quality. Used extensively on the Web, JPEG and GIF are common compressed image file formats. See also, file compression.

Instant Message: a program that allows two or more people to communicate with one another over the Internet in real time; while most IM communications occur as text, some IM programs also offer streaming audio-visual conferencing and file exchange services. IM can also refer to messages sent by instant messaging, or to the act of sending an instant message.

Internet Protocol address: a unique identifier for each computer or other device on a network, including the Internet. Conceptually similar to a phone number, IP addresses are a string of numbers that allow computers, routers, printers, and other devices to recognize [identify] one another and communicate.

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. The file extension for JPEGs is .jpg or .jpeg. See also, GIF.

Software that monitors and captures everything a user types into a computer keyboard. Used for technical support and surveillance purposes; can also be integrated into malware and used to gather passwords, user names, and other private information.

Derived from malicious software: software designed to do harm by causing damage to systems or data, invading privacy, stealing information, or infiltrating computers without permission; includes viruses, worms, Trojan horses, and some keyloggers, spyware, adware, and bots.

mpeg audio layer 3: a compressed audio file format, popular for playing sound and music recordings over handheld and desktop audio players.

Personal Digital Assistant: a handheld computer usually containing address books, memo pads, and other personal organization software. Many PDAs can connect to the Web, send email, and synchronize with home computers; some work as cellular phones.

Phishing is essentially an online con game and phishers are nothing more than tech-savvy con artists and identify thieves. They use SPAM, malicious Web sites, email messages and instant messages to trick people into divulging sensitive information, such as bank and credit card accounts.

The process of using backups to restore original data files that have been damaged or are no longer accessible.

A hardware device that connects two networks and directs traffic from one network to the appropriate destination on the other. Often used to connect a network to the Internet, some routers have network firewalls and other features built into them.

Really Simple Syndication: an XML format used to create Web feeds of content available on news sites, blogs, and other Web sites with fast-changing information. The feeds generally contain headlines and summaries of content, and subscribers use RSS readers to view them.

Unsolicited email, usually sent in bulk to a large number of random accounts; often contain ads for products or services. Also used in phishing scams and other online fraud. Can be minimized using email filtering software.

Unsolicited instant messages, usually sent in bulk to a large number of IM accounts; often contain marketing materials and links to product Web pages. May also be used in phishing scams or to spread malware.

spam over Internet telephony; unsolicited VoIP phone calls sent in bulk over the Internet. Not yet a major annoyance or threat, but could become a serious problem as VoIP becomes more popular. See also, spam and spim.

A program that can self-replicate and infect files, programs, and computer systems; some viruses simply replicate and spread themselves, while others can also damage your computer system and data.

A program used to download, display, and navigate among Web pages. Web browsers primarily use HTTP to communicate, and they can display a variety of files types, including HTML, XML, JPEG, GIF, and MPEG. Most browsers can run small programs written in Java, ActiveX, and JavaScript, and many can encrypt transmissions for security purposes.

A bot that methodically browses the Web. Used by search engines to automatically download a vast number of Web sites, which are then indexed to make searches more efficient. Can also be used to do Web site maintenance or to harvest email addresses for spam purposes.

A file, usually in HTML format, available for retrieval by a browser on the Web. Web pages can contain text, images, and multi-media resources. They usually include hyperlinks to other Web pages or files, and some contain forms through which you can send information to the page host.

A physical area where you can use a Wi-Fi-enabled device to connect to the Internet over a public wireless network. Some hotspots have no security measures in place, while others use WEP or WPA to secure transmissions.