U-W

Unauthorized access

A user gains access without permission to a network, system, application, data, or other resource.

Vaccine

A program that injects itself into an application in order to perform a signature check and provide a warning if alterations are detected .

Victim

A machine or system that is attacked .

Virtual network perimeter

A network that appears to be a single protected network behind firewalls, which actually encompasses encrypted virtual links over untrusted networks.

Virtual Private Network (VPN)

A way of using a public network (typically the Internet) to link two sites of an organization. A VPN is typically set up by protecting the privacy and integrity of the communication line using a secret session key. The secret session key is usually negotiated using the public keys of the two principals.

Virus

Malicious code that self-replicates and attaches itself to an application or other executable and leaves no obvious signs of its presence. The new copy of the virus is executed when a user executes the new, copied host program. The virus may include an additional "payload" that triggers when specific conditions, such as time of day or specific date are met. For example, some viruses display a text string on a particular date. There are many types of viruses, such as variants, overwriting, resident, stealth, and polymorphic.

Virus hoax

An urgent warning message about a nonexistent virus.

Vulnerability

A weakness in a system, application, or network that is subject to exploitation or misuse. An exploitable flaw or weakness in an information infrastructure.

Vulnerability analysis

An evaluation of vulnerabilities in an information infrastructure.

Vulnerability assessment

A complete, orderly examination of an information system and/or infrastructure to determine the adequacy of security measures, identify any security vulnerabilities, gather data that will be used to predict the effectiveness of any proposed security measures, and confirm the adequacy of such measures postimplementation.

War dialer

A program that autodials a list of numbers and records those that answer with handshake responses, indicating possible entry points to networked systems.

War-driving

The process of using a war dialer in a wireless or mobile environment where the hacker is often moving from location to location scanning for vulnerable computer systems and cataloging those numbers that return a handshake response so a crack can be attempted at a later time to try to infiltrate the system.

Wide Area Network (WAN)

A data communications network that spans any distance and is usually provided by a public carrier. Users gain access to the two ends of the circuit, and the carrier handles the transmission and other services in between.

Worm

1. A self-replicating, self-propagating, self-contained program that uses networking mechanisms to spread itself. 2. An insidious, self-contained program that replicates from machine to machine across network connections, often clogging networks as it spreads . 3. A self-replicating program, self-contained executable, able to propagate without need of a host program. The program creates a copy of itself and causes the copy to execute without user intervention. Worms commonly use network services to propagate to other host systems.