Uauth: User authentication
User authentication (Uauth) is a method to control access to certain restricted areas of information or a system by requiring user identification such as user name and password.

UDP Flood
A UDP Flood Attack is possible when an attacker sends a UDP packet to a random port on the victim system. When the victim system receives a UDP packet, it will determine what application is waiting on the destination port. When it realizes that there is no application that is waiting on the port, it will generate an ICMP packet of destination unreachable to the forged source address. If enough UDP packets are delivered to ports on victim, the system will go down.

UDP Scan
UDP Scan, also known as UDP port scan, refers to performing port scans to determine which UDP ports are open. UDP scan can be used by attackers to launh attacks or for legitimate reasons.

UDP port scanning
UDP port scanning is the process of performing port scans to determine which User Datagram Protocol (UDP) ports are open. UDP scan can be used by attackers to launh attacks or for legitimate reasons.

UDP tunneling
UDP tunneling refers to a method of using User Datagram Protocol (UDP) to establish a covert channel.

Unprotected Share
In Windows terminology, a "share" is a mechanism that allows a user to connect to file systems and printers on other systems. An "unprotected share" is one that allows anyone to connect to it.

Untrusted Process
Untrusted Process is a system process that cannot affect the state of system security through incorrect or malicious operation, usually because its operation is confined by a security kernel.

URI: Uniform Resource Identifier
URI is the generic term for all types of names and addresses that refer to objects on the World Wide Web.

URL Poisoning
URL poisoning, also known as location poisoning, is a method of tracking Web user behavior by adding an identification (ID) number to the page address (Uniform Resource Locator) line of the Web browser when a user visits a particular site. This ID number can then be used to determine which pages on the site the user visits thereafter.

URLScan
URLScan is a tool for securing Microsoft Internet Information Services (IIS).

User
In computing and networking, a user is a person, organization entity, or automated process that accesses a system, whether authorized to do so or not.

URL: Uniform Resource Locator
The global address of documents and other resources on the World Wide Web. The first part of the address indicates what protocol to use, and the second part specifies the IP address or the domain name where the resource is located. For example, http://www.pcwebopedia.com/index.html .

User Contingency Plan
User Contingency Plan is the alternative methods of continuing business operations if IT systems are unavailable.

User Profile
In a Windows environment, a user profile is a record of user-specific data that defines the user's working environment. The record can include display settings, application settings, and network connections. What the user sees on his or her computer screen, as well as what files, applications and directories they have access to, is determined by how the network administrator has set up the user's profile.

User Profiling
User profiling is a mechanism to assign several descriptive features to a user. User profiling involves developing a profile of the user concerned. The profile can be built by a history of events and actions. It therefore involves monitoring the user's behavior. Any behavior "out-of-character" would trigger a silent alarm to an administrator who could investigate further.

User2sid
User2sid  is a tool for obtaining the security identifier (SID) associated with a user name.

UserDump
UserDump is a tool for enumerating user accounts on Microsoft Windows–based systems.

User-level security
User-level security refers to protecting shared resources using user authentication.

UTM: Unified Threat Management
Unified Threat Management(UTM) refers to the technologies in the firewall appliance that not only guards against intrusion but performs content filtering , spam filtering, intrusion detection and anti-virus duties traditionally handled by multiple systems. Rather than administer multiple systems that handle Anti-virus, Content Filtering, Intrusion Detection and Spam Filtering, companies can use a Unified Threat Management (UTM) Firewall Appliance that integrates all of the above into a single rack mountable network appliance.

UUdecode: UNIX-to-UNIX Decode
UNIX-to-UNIX decode (Uudecode) is a method of decoding ASCII files that were encoded using UNIX-to-UNIX encoding (Uuencode).

UUE: UUEncode
UNIX-to-UNIX encoding (Uuencode) is a method of converting binary files to ASCII so they can be sent over the Internet over the UUCP mail system. Since UUCP converted characters between various computer's character sets, uuencode was used to convert the data to fairly common characters that were unlikely to be "translated" and thereby destroy the file. The program uudecode reverses the effect of uuencode, recreating the original binary file exactly. uuencode/decode became popular for sending binary files by e-mail and posting to usenet newsgroups etc. It has now been largely replaced by MIME.