R

radio frequency (RF)

The part of the radio spectrum that a device uses.

radio frequency interference (RFI)

The byproduct of electrical processes, similar to electromagnetic interference. The major difference is that RFI is usually projected across a radio spectrum.

RADIUS

See Remote Authentication Dial-In User Service (RADIUS).

RAID

See Redundant Array of Independent (or Inexpensive) Disks (RAID).

RAID levels

The different types of RAID, such as RAID-0, RAID-1, and so on.

RAS

See Remote Access Server (RAS).

RBAC

See Role-Based Access Control (RBAC).

RC5

See Rivest Cipher 5 (RC5).

Redundant Array of Independent (or Inexpensive) Disks (RAID)

A configuration of multiple hard disks used to provide fault tolerance, should a disk fail, or gains in efficiency. Different levels of RAID exist.

registration authority (RA)

An organization that offloads some of the work from a certificate authority (CA). An RA system operates as a middleman in the process. The RA can distribute keys, accept registrations for the CA, and validate identities. The RA doesn't issue certificates; that responsibility remains with the CA.

relying party

The person receiving a certificate.

remote access protocol

Any networking protocol that is used to gain access to a network over public communication links.

remote access server (RAS)

A computer that has one or more modems installed to enable remote connections to the network.

Remote Authentication Dial-In User Service (RADIUS)

A mechanism that allows authentication of dial-in and other network connections. RADIUS is commonly used by Internet service providers (ISPs) and in the implementation of virtual private networks (VPNs).

replay attack

Any attack where the data is retransmitted repeatedly (often fraudulently or maliciously). In one such possibility, a user can replay a web session and visit sites intended only for the original user.

replication

The process of copying directory information to other servers to keep them all synchronized.

repository

A database or database server where the certificates are stored.

repudiation attack

An attack in which the intruder modifies information in a system.

Request for Comments (RFC)

A document creation process and a set of practices that originated in 1969 and is used for proposed changes to Internet standards.

response

How you react to an event.

restricted information

Information that isn't made available to all and to which access is granted based on some criteria.

retrovirus

A virus that attacks or bypasses the antivirus software installed on a computer.

reverse DNS

Using an IP address to find a domain name rather than using a domain name to find an IP address (normal DNS). Pointer (PTR) records are used for the reverse lookup, and often reverse DNS is used to authenticate incoming connections.

reverse engineering

The process of re-creating the functionality of an item by first deciding what the result is and then creating something from scratch that serves the same purpose.

revocation

The process of canceling credentials that have been lost or stolen (or are no longer valid). With certificates, revocation is accomplished with a Certificate Revocation List (CRL).

RIP

See Routing Information Protocol (RIP).

risk analysis

An evaluation of each risk that can be identified. Each risk should be outlined, described, and evaluated on the likelihood of it occurring.

risk assessment

An evaluation of how much risk you and your organization are willing to take. An assessment must be performed before any other actions—such as how much to spend on security in terms of dollars and manpower—can be decided.

Rivest Cipher 5 (RC5)

A cipher algorithm created by Ronald Rivest (for RSA) and known for its speed. It works through blocks of variable sizes using three phases: key expansion, encryption, and decryption.

roaming profile

A profile downloaded from a server at each logon. When a user logs out at the end of the session, changes are made and remembered for the next time the user logs on.

rogue server

An active Dynamic Host Configuration Protocol (DHCP) server that has been added to the network and is now leasing addresses to users instead of them obtaining an address from your server.

Role-Based Access Control (RBAC)

A type of control wherein the levels of security closely follow the structure of an organization. The role the person plays in the organization (accountant, salesman, and so on) corresponds to the level of security access they have to data.

rootkit

Software program that has the ability to obtain root-level access and hide certain things from the operating system.

route

The path to get to the destination from a source.

route cost

The number of router hops between the source and the destination in an internetwork.

router

A device that connects two or more networks and allows packets to be transmitted and received between them. A router determines the best path for data packets from source to destination.

routing

A function of the Network layer that involves moving data throughout a network. Data passes through several network subnetworks using routers that can select the path the data takes. See also router.

Routing Information Protocol (RIP)

A distance-vector route discovery protocol used by Internetwork Packet Exchange (IPX) and Internet Protocol (IP). IPX uses hops and ticks to determine the cost for a particular route. See also Internetwork Packet Exchange (IPX).

routing table

A table that contains information about the locations of other routers on the network and their distance from the current router.

RSA

One of the providers of cryptography systems to industry and government. RSA stands for the initials of the three founders of RSA Security Inc.: Rivest, Shamir, and Adleman. RSA maintains a list of standards for Public Key Cryptography Standards (PKCS).

RSA

A commercial company that produces encryption software. RSA stands for Rivest, Shamir, and Adleman, the founders of the company.

RSBAC

See Rule Set-Based Access Control (RSBAC).

Rule Set-Based Access Control (RSBAC)

An open-source access control framework for the Linux kernel that uses access control modules to implement Mandatory Access Control (MAC).