[#aaasecur]: AAA (security)

The abbreviation “AAA” could have multiple meanings. In the United States of America, generations born in the 1950's and earlier may be most familiar with the term referring to an organization called the American Automobile Association. The abbreviation may also refer to a grading scale, where AA is a higher grade than A and AAA is two grades higher than A.

In the computer industry, the term often refers to “Authentication, Authorization, and Accounting”.


authentication is different than authorization.


Determining permission. Most often this is probably for a person or computer that has been successfully authenticated, although it could simply be part of some sort of audit that is checking whether permission levels are set up as desired.


The third A stands for “accounting”, although sometimes sometimes the A refers to the word “auditing” (another word starting with “a”), or even “accounting and auditing”. Regardless of which word or phrase the A stands for, the concept is the same: it relates to “logging”. Have a record of activity.

(Discussed further in the section about accounting).

See Augmented BNF.
[#acl]: Access Control List (“ACL”)

A set of rules that helps to determine whether or not access should be provided.

ACLs in Microsoft Windows

An ACL contains an Access Control Entry (“ACE”) or, more likely, multiple ACEs. There are two types of ACLs: A “descretionary ACL” (“DACL”) is what is commonly used for authorizing (determining whether or not security access should be granted). A SACL is used for auditing.


The industry of accounting typically has to do with finances, and refers to determining facts about money (like how much money is available).

The way the term applies to the computer security industry is that accounting is related to figuring out what happened (which can help to describe what a current situation is).

Really, this is a fancy way of saying “logging”. The term is used both by the BSD acct command, and by the term “AAA” (which might be a term that is most frequently used when discussing Cisco equipment that implements AAA).

The logging could refer to login requests, network connection creation, or other network activity, or other activity. See: Logs, logging user account activity.

[#apipaabr]: APIPA

An abbreviation for “Automatic Private IP Addressing”. (“IP” is itself an abbreviation within the standard meaning of the APIPA abbreviation.) See: Automatic Private IP Addressing (“APIPA”), IPv4 Link-Local Addresses (RFC 3927: Dynamic Configuration of IPv4 Link-Local Addresses), Internet Protocol Automatic Configuration (“IPAC”), Zero configuration networking (“zeroconf”, perhaps “zconf”)

[#apipa]: Automatic Private IP Addressing (“APIPA”)

For some official documentation, see: APIPA's main page, Q220874: How to use automatic TCP/IP addressing without a DHCP server. Historically Microsoft had called this “Internet Protocol Automatic Configuration” (“IPAC”).

RFC 3927 (hyperlinked below) describes standards-compliant behavior. RFC 3927: Dynamic Configuration of IPv4 Link-Local Addresses: Appendix A-3: Behavior of Microsoft Windows 98/98SE lets us know that “If Windows 98/98SE is successful at obtaining a new lease, it drops all existing connections without warning. This may cause users to lose sessions in progress.” Oh, how kind. As for some newer software, it seems to fare no better: RFC 3927: Dynamic Configuration of IPv4 Link-Local Addresses: Appendix A-4: Behavior of Microsoft Windows ME, 2K, and XP says “The autoconfiguration behavior of Windows XP, Windows 2000, and Windows ME systems is identical to Windows 98/98SE except” for some exceptions which don't mention a change to prevent dropping connections.

For some other similar technologies, see the RFC 3927 described above, Cyber Pillar's section(s) on IPv4 automatic addressing (hyperlink: improvable by getting more specific?), Zero configuration networking (“zeroconf”, perhaps “zconf”).

[#abnf]: Augmented BNF (“ABNF”)

See RFC 5234. Also, for something similar, see Extended Backus-Naur Form.

[#ahci]: Advanced Host Controller Interface (“AHCI”)
Part of SATA standard which is needed to support hot swapping, AHCI also supports the Native Command Queuing feature that improves SATA speed. It appears software support may be needed: perhaps Vista has this and XP doesn't. See http://support.microsoft.com/kb/922976. Supporting AHCI may require enabling support in a BIOS setup option where AHCI is chosen instead of Legacy/IDE compatibility mode. If one of the motherboard's features is that the motherborad provides RAID support, then RAID may be a third option (other than AHCI or Legacy/IDE compatibility mode), so choosing the “AHCI” option would involve not selecting the option for the BIOS-provided RAID. (However, using the RAID option may, or perhaps usually does, involve using AHCI.)
[#ahciabbr]: AHCI
See Advanced Host Controller Interface. (This has been related to SATA.)
[#advtch]: “Advanced Technology” (AT)

The phrase originally stood for “Advanced Technology”. Now, it typically refers to technology dating back to the time when IBM released the PC AT (which used a 286 CPU). So, like Microsoft's more recent “NT” (“New Technology”), the term's current usage does not match what the name stands for.

Note: There is a command line scheduling program called at, which is spelled like “AT” but is lowercase. However, this command has nothing to do with this “AT” acronym.

[#asset]: asset (computer security term)

The term “asset” refers to what has value. A definition that is commonly given is that an asset is “something which has value”. However, do not get too focused on the word “thing”. A physical object, such as a brand new computer, has value and, therefore, is an asset. However, intangible “things” can also have asset. Information is commonly considered to be more valuable than the computer hardware that is being used to store that information. A company's brand name may have a positive reputation, and so that reputation may be an asset. Whatever has any value, of any sort, is considered to be an asset.

[#ata]: AT Attachment (“ATA”)

(E)IDE style drives using this form of parallel communication used a communications standard called “ATA”. That standard has since been renamed, and the currently used phrase is “PATA” (which stands for “parallel ATA”). The newer standard of SATA (which stands for “serial ATA”) sends less traffic simultaneously, resulting in less interference caused by cross-talk. The lack of cross-talk allows the bits to at higher speed (by sending bits more frequently, rather than trying to send more all at once).

The phrase “AT Attachment” refers to IBM's older AT platform.

[#atapi]: ATA Packet Interface (“ATAPI”)

ATAPI was initially an add-on to an older version of the ATA standard. Since then, ATAPI became a part of a newer version of the ATA standard. The ATAPI extension provided the ability for certain SCSI packets to be communicated over the ATA interface. This allowed a fairly compatible method to support sending certain commands to drives, such as asking a drive with removable media to eject the media.

The meaning of ATAPI is “ATA Packet Interface”, where “ATA” is itself an acronym for “Advanced Technology”. So, the phrase ATAPI came from double acronymization.

[#authenct]: authenticate/authentication

Authentication is simply the process of performing the action known as “authenticate”.

Determining who a person is. See: user authentication, multifactor authentication.

[#autonosy]: autonomous system (“AS”)
Autonomous System (as centralized by IANA)

A network, or networks, where an individual authority can specify how network traffic routing operates. (The term “network” may refer to network infrastructure equipment, or may be focused less on the actual equipment and more on the network routes. The distinction being made is that even if changes occur regarding what equipment is being used, the IP networks/subnets don't change, so network routes remains part of the same AS.) Cisco documentation (Discovery 4.0 module 2 slide has noted, “The most common example of an AS is the ISP.” The customers relying on the ISP have their routes being controlled by the ISP, so multiple different customers may effectively end up being part of the same AS. All equipment in an AS routing domain may use an identical “autonomous system number” (“ASN”). This is true despite the fact that the equipment by an ISP subscriber may ultimately be owned and operated by someone other than the ISP. Since the ISP controls the routing of traffic to and from the device, the device ends up being part of the ISP's AS.

Related term:

Transit Traffic (vs. Local Traffic)

Network traffic traveling through an AS, which originated from a different AS, but is intended to travel to yet another AS. In contrast, “Local Traffic” is for traffic that is expected to end within the AS, or traffic which originated from the AS.

Other, unrelated types of Autonomous System

Some routing protocols may have an “Autonomous System”, including OSPF and EIGRP. An Autonomous System refers to a group of IP addresses and/or devices and/or routes. In concept, this might function quite similar to an AS provided by IANA. However, these Autonomous Systems are locally assigned, rather than being centralized by a global organization. This basically means that people can legitimately choose their own number to use as an AS, without concern of interfering with operations by someone else who picks the same AS.