Blacklist (computing)
Encyclopedia
In computing
, a blacklist or block list is a basic access control
mechanism that allows everyone access, except for the members of the black list (i.e. list of denied accesses). The opposite is a whitelist, which means allow nobody, except members of the white list. As a sort of middle ground, a greylist
, contains entries that are temporarily blocked or temporarily allowed. Greylist items may be reviewed or further tested for inclusion in a blacklist or whitelist.
An organization may keep a blacklist of software or websites in its computer system. Titles on the list would be banned and everything else would be allowed. For example, a school might blacklist Limewire
and ICQ
; other Internet services would still be allowed.
Computing
Computing is usually defined as the activity of using and improving computer hardware and software. It is the computer-specific part of information technology...
, a blacklist or block list is a basic access control
Access control
Access control refers to exerting control over who can interact with a resource. Often but not always, this involves an authority, who does the controlling. The resource can be a given building, group of buildings, or computer-based information system...
mechanism that allows everyone access, except for the members of the black list (i.e. list of denied accesses). The opposite is a whitelist, which means allow nobody, except members of the white list. As a sort of middle ground, a greylist
Greylisting
Greylisting is a method of defending e-mail users against spam. A mail transfer agent using greylisting will "temporarily reject" any email from a sender it does not recognize. If the mail is legitimate the originating server will, after a delay, try again and, if sufficient time has elapsed, the...
, contains entries that are temporarily blocked or temporarily allowed. Greylist items may be reviewed or further tested for inclusion in a blacklist or whitelist.
An organization may keep a blacklist of software or websites in its computer system. Titles on the list would be banned and everything else would be allowed. For example, a school might blacklist Limewire
LimeWire
LimeWire is a free peer-to-peer file sharing client program that runs on Windows, Mac OS X, Linux, and other operating systems supported by the Java software platform. LimeWire uses the gnutella network as well as the BitTorrent protocol. A free software version and a purchasable "enhanced"...
and ICQ
ICQ
ICQ is an instant messaging computer program, which was first developed and popularized by the Israeli company Mirabilis, then bought by America Online, and since April 2010 owned by Mail.ru Group. The name ICQ is a homophone for the phrase "I seek you"...
; other Internet services would still be allowed.
Examples
- Companies like GoogleGoogleGoogle Inc. is an American multinational public corporation invested in Internet search, cloud computing, and advertising technologies. Google hosts and develops a number of Internet-based services and products, and generates profit primarily from advertising through its AdWords program...
, NortonNorton-England:*Norton, County Durham*Norton, Hertfordshire*Norton, Kent*Norton, Northamptonshire*Norton, Nottinghamshire*Norton, Runcorn, Cheshire*Norton, Suffolk*Norton, Dudley, West Midlands*Norton, Worcester, Worcestershire*Norton, Doncaster, South Yorkshire...
and SucuriSucuriSucuri is a company that offers a security service that detects unauthorized changes to network assets, including web sites, DNS, Whois records, SSL certificates and others...
keep internal blacklists of sites known to have malware and they display a warning before allowing the user to click them. - Content-control softwareContent-control softwareContent-control software, also known as censorware or web filtering software, is a term for software designed and optimized for controlling what content is permitted to a reader, especially when it is used to restrict material delivered over the Web...
such as DansGuardianDansGuardianDansGuardian, written by SmoothWall Ltd and others, is content-control software: software designed to control which websites users can access. It also includes virus filtering and usage monitoring features...
and SquidGuard may work with a blacklist in order to block URLsUniform Resource LocatorIn computing, a uniform resource locator or universal resource locator is a specific character string that constitutes a reference to an Internet resource....
of sites deemed inappropriate for a work or educational environment. - An e-mail spamE-mail spamEmail spam, also known as junk email or unsolicited bulk email , is a subset of spam that involves nearly identical messages sent to numerous recipients by email. Definitions of spam usually include the aspects that email is unsolicited and sent in bulk. One subset of UBE is UCE...
filter may keep a blacklist of addresses, any mail from which would be prevented from reaching its intended destination. A popular technique for implementing blacklists is DNS blacklistingDNSBLA DNSBL is a list of IP addresses published through the Internet Domain Name Service either as a zone file that can be used by DNS server software, or as a live DNS zone that can be queried in real-time...
(DNSBL). - A firewallFirewall (computing)A firewall is a device or set of devices designed to permit or deny network transmissions based upon a set of rules and is frequently used to protect networks from unauthorized access while permitting legitimate communications to pass....
or IDS may also use a blacklist to block known hostile IPs and/or networks. An example for such a list would be the OpenBL project. - Many copy protectionCopy protectionCopy protection, also known as content protection, copy obstruction, copy prevention and copy restriction, refer to techniques used for preventing the reproduction of software, films, music, and other media, usually for copyright reasons.- Terminology :Media corporations have always used the term...
schemes include software blacklistSoftware blacklistSoftware blacklisting is a tool used by manufacturers of software and music on CD and DVD to prevent copying.Essentially the software on the disc will audit the user's computer for certain types of virtual CD and CD authoring software, or for debugging software used by warez groups to create...
ing. - Members of online auction sites may add other members to a personal blacklist. This means that they cannot bid on or ask questions about your auctions, nor can they use a "buy it now" function on your items.
- Yet another form of list is the yellow list which is a list of email server IP addresses that send mostly good email but do send some spam. Examples include Yahoo, HotmailHotmailWindows Live Hotmail, formerly known as MSN Hotmail and commonly referred to simply as Hotmail, is a free web-based email service operated by Microsoft as part of its Windows Live group. It was founded by Sabeer Bhatia and Jack Smith and launched in July 1996 as "HoTMaiL". It was one of the first...
, and GmailGmailGmail is a free, advertising-supported email service provided by Google. Users may access Gmail as secure webmail, as well via POP3 or IMAP protocols. Gmail was launched as an invitation-only beta release on April 1, 2004 and it became available to the general public on February 7, 2007, though...
. A yellow listed server is a server that should never be accidentally blacklisted. The yellow list is checked first and if listed then black list tests are ignored. - In LinuxLinuxLinux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
modprobeModprobemodprobe is a Linux program originally written by Rusty Russell and used to add a loadable kernel module to the Linux kernel or to remove an LKM from the kernel...
, theblacklist modulenameentry in a modprobe configuration file indicates that all of the particular moduleLoadable Kernel ModuleIn computing, a loadable kernel module is an object file that contains code to extend the running kernel, or so-called base kernel, of an operating system...
's internal aliases are to be ignored. There are cases where two or more modules both support the same devices, or a module invalidly claims to support a device. - Many browsers have the ability to consult anti-phishingPhishingPhishing is a way of attempting to acquire information such as usernames, passwords, and credit card details by masquerading as a trustworthy entity in an electronic communication. Communications purporting to be from popular social web sites, auction sites, online payment processors or IT...
blacklists in order to warn users who unwittingly aim to visit a fraudulent websiteInternet fraudInternet fraud refers to the use of Internet services to present fraudulent solicitations to prospective victims, to conduct fraudulent transactions, or to transmit the proceeds of fraud to financial institutions or to others connected with the scheme....
. - Many P2PPeer-to-peerPeer-to-peer computing or networking is a distributed application architecture that partitions tasks or workloads among peers. Peers are equally privileged, equipotent participants in the application...
programs support blacklists that block access from sites known to be owned by Intellectual PropertyIntellectual propertyIntellectual property is a term referring to a number of distinct types of creations of the mind for which a set of exclusive rights are recognized—and the corresponding fields of law...
holders. An example is the Bluetack blocklist set.