Adware

Software that delivers advertising to your PC, perhaps in the form of popups or sidebars with scrolling adverts.

DDoS

Distributed Denial of Service. A DoS or DDoS attack is an attempt to ?choke up? an internet connection or server, typically by flooding it with junk data. Botnets are often used for DDoS attacks ? hundreds of computers work to shut down an Internet connection or server.

Dumpster diving

The practice of sifting through garbage bins (commercial or domestic) for documents that have been thrown away as ?rubbish?, but which might be useful to the dumpster diver.

Firewall

Software or hardware that blocks network traffic. A firewall tries to distinguish ?good traffic? from ?bad traffic?. Good traffic is allowed to pass, bad traffic is blocked.

Malware

A catch-all term for software that does undesirable things to your computer. Viruses, worms and Trojans are all forms of malware.

Patch

A software update designed to fix problems in the shipped versions of products. For example, a security flaw might be found in a piece of software after it has shipped to retailers. So the software developer writes a ?patch? that fixes the flawed parts, and distributes that patch over the internet.

Phishing

Using email or a fake website to trick people into giving up private information, such as credit card details. The most common example is the email that purports to be from a bank. The email asks the receiver to go to a specific website and log in using their internet banking username and password. The site looks real enough, but in reality all it is doing is harvesting the user?s details. A technique called spear phishing is an evolution of that ? it targets specific individuals to make the phishing attempt sound more plausible.

Script kiddie

A person who uses readily available internet tools to perform basic attacks on computer systems. For instance, a person who uses a downloadable port scanner to find vulnerabilities (such as file shares and open directories on a Windows system), then perhaps uses a downloaded password hacking program to access those vulnerabilities.

Spam

Unwanted email (the equivalent of junk mail), usually advertising, sent out by mass mailers. A spam filter detects and removes spam from email inboxes.

Spyware

Software that sits on your computer and monitors your activity, creating and possibly sending reports to hostile parties.

Trojan

A type of program that installs malicious software (such as viruses) while under the pretence of doing something else. Over time, the term Trojan has become almost synonymous with a type of virus that sits resident on the computer to create a ?backdoor? that hackers can exploit to get into the host system. The Trojan on an infected system will often advertise itself to the creator of the Trojan or other parties, although a good software firewall will prevent that advertisement from getting out (and it will also stop remote hackers from getting in a accessing the backdoor)

Vaccine

A program that injects itself into an executable program to perform a signature check and warns if there have been any changes.

Virus

Malicious software that ?infects? a computer system, causing it to do undesirable things (like deleting files, dialling 1800 numbers on the modem or sending private data to remote parties over the internet). Anti-virus software detects and removes viruses.

Worm

A form of virus that replicates itself over a network. When a worm infects a system, it will use that system to try and infect other systems. The classical example is the email worm; the worm sends out a copy of itself to every user in the host PC?s email address book (and the recipients, seeing that the sender is someone they know, might be inclined to trust the email enough to open the file).

Zombie

A ?zombie? is a computer with a remote control Trojan installed. It works normally, but the Trojan remains as a silent agent, waiting for its ?master? (often the creator of the Trojan) to take control of the system. A bot is an application running on a zombie, installed by the zombie master to undertake some task ? often a denial of service attack (see DDoS opposite) or sending out spam. A botnet is a group of bots infected by the same Trojan, and can be used in conjunction to perform distributed attacks.