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Whitelist
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A whitelist or allowlist is a list or register of entities that are being provided a particular privilege, service, mobility, access or recognition. Entities on the list will be accepted, approved and/or recognized. Whitelisting is the reverse of blacklisting, the practice of identifying entities that are denied, unrecognized, or ostracized.[citation needed]
Email whitelists
[edit]Spam filters often include the ability to "whitelist" certain sender IP addresses, email addresses or domain names to protect their email from being rejected or sent to a junk mail folder. These can be manually maintained by the user[1] or system administrator - but can also refer to externally maintained whitelist services.[citation needed][2]
Non-commercial whitelists
[edit]Non-commercial whitelists are operated by various non-profit organizations, ISPs, and others interested in blocking spam. Rather than paying fees, the sender must pass a series of tests; for example, their email server must not be an open relay and have a static IP address. The operator of the whitelist may remove a server from the list if complaints are received.[citation needed][3]
Commercial whitelists
[edit]Commercial whitelists are a system by which an Internet service provider allows someone to bypass spam filters when sending email messages to its subscribers, in return for a pre-paid fee, either an annual or a per-message fee. A sender can then be more confident that their messages have reached recipients without being blocked, or having links or images stripped out of them, by spam filters. The purpose of commercial whitelists is to allow companies to reliably reach their customers by email.[citation needed]
Advertising whitelist
[edit]Many websites rely on ads as a source of revenue, but the use of ad blockers is increasingly common.[citation needed] Websites that detect an adblocker in use often ask for it to be disabled - or their site to be "added to the whitelist"[4] - a standard feature of most adblockers.[citation needed]
Network whitelists
[edit]LAN whitelists
[edit]A use for whitelists is in local area network (LAN) security. Many network admins set up MAC address whitelists, or a MAC address filter, to control who is allowed on their networks. This is used when encryption is not a practical solution or in tandem with encryption. However, it's sometimes ineffective because a MAC address can be faked.[citation needed]
IP whitelist
[edit]Firewalls can usually be configured to only allow data-traffic from/to certain (ranges of) IP-addresses.[citation needed]
Application whitelists
[edit]One approach in combating viruses and malware is to whitelist software which is considered safe to run, blocking all others.[5][6][7][8] This is particularly attractive in a corporate environment, where there are typically already restrictions on what software is approved.[citation needed]
Leading providers of application whitelisting technology include Bit9, Velox, McAfee, Lumension, ThreatLocker, Airlock Digital and SMAC.[9][10][11]
On Microsoft Windows, recent versions include AppLocker, which allows administrators to control which executable files are denied or allowed to execute. With AppLocker, administrators are able to create rules based on file names, publishers or file location that will allow certain files to execute. Rules can apply to individuals or groups. Policies are used to group users into different enforcement levels. For example, some users can be added to a report-only policy that will allow administrators to understand the impact before moving that user to a higher enforcement level.[citation needed]
Linux systems typically have AppArmor and SE Linux features available which can be used to effectively block all applications which are not explicitly whitelisted, and commercial products are also available.[12]
On HP-UX introduced a feature called "HP-UX Whitelisting" on 11iv3 version.[13]
Controversy regarding name
[edit]In 2018, a journal commentary on a report on predatory publishing[14] was released making claims that "white" and "black" are racially charged terms that need to be avoided in instances such as "whitelist" and "blacklist". The journal became mainstream in Summer 2020 following the George Floyd protests in America[15] wherein a black man was murdered by an officer, sparking protests on police brutality.
The premise of the journal is that "black" and "white" have negative and positive connotations respectively.[14] It states that since "blacklisting" was first referred to during "the time of mass enslavement and forced deportation of Africans to work in European-held colonies in the Americas," the word is therefore related to race. There is no mention of "whitelist" and its origin or relation to race.
This issue is most widely disputed in computing industries where "whitelist" and "blacklist" are prevalent (e.g. IP whitelisting[16]). Despite the commentary nature of the journal, some companies and individuals in others have taken to replacing "whitelist" and "blacklist" with new alternatives such as "allow list" and "deny list".[17] Those adopting this change consider using the "whitelist"/"blacklist" names as a code smell.[18]
Those that oppose these changes question its attribution to race, citing the same etymology quote that the 2018 journal uses.[17][19] According to the remark, the term "blacklist" evolved from the term "black book" about a century ago. The term "black book" does not appear to have any etymology or sources that support racial associations, instead originating in the 1400s as a reference to "a list of people who had committed crimes or fallen out of favor with leaders", and popularized by King Henry VIII's literal use of a black book.[20] Others also note the prevalence of positive and negative connotations to "white" and "black" in the Bible, predating attributions to skin tone and slavery.[21] It wasn't until the 1960s Black Power movement that "Black" became a widespread word to refer to one's race as a person of color in America[22] (alternate to African-American) lending itself to the argument that the negative connotation behind "black" and "blacklist" both predate attribution to race.
See also
[edit]- Blacklisting
- Blacklist (computing)
- Blackballing
- Closed platform
- DNSWL, whitelisting based on DNS
- Opt-in
References
[edit]- ^ e.g. Kindle users control the whitelist for email access. Besides Amazon itself, only e-mail addresses whitelisted by the device's registered owner can send content ("personal documents") to that device.
- ^ "IP and domain reputation". Spamhaus Project.
- ^ "Spamhaus' Blocklists".
- ^ "Adblock Instructions". Forbes. Retrieved 2017-12-09.
- ^ John Harrison, Enhancing Network Security By Preventing User-Initiated Malware Execution, Proceedings of the International Conference on Information Technology: Coding and Computing (ITCC'05) (Wireless Ad Hoc/Sensor Networks and Network Security Track), Volume II - Volume 02; pages 597-602; IEEE Computer Society Washington, DC, USA 2005.
- ^ "SANS Institute: Reading Room - Analyst Papers" (PDF). www.sans.org. Archived from the original (PDF) on 2012-03-02. Retrieved 27 August 2018.
- ^ "Dark Reading - Security - Protect The Business - Enable Access". Dark Reading. Archived from the original on 2019-12-12. Retrieved 2008-10-02.
- ^ "Application Whitelisting Gains Traction". eweek.com. 25 September 2008.
- ^ Blum, Dan (February 8, 2014). "Lessons Learned from Target Breach". Security-Architect Blog. Dan Blum. Retrieved July 18, 2014.
- ^ Vamosi, Robert (2008-07-21). "Will you be ditching your antivirus app anytime soon?". CNET. Archived from the original on 2012-10-24. Retrieved 2010-03-22.
- ^ Korobov, EVGENIY (2020-07-27). "SMAC - application whitelist platform". iqp. Archived from the original on 2020-07-27. Retrieved 2020-07-27.
- ^ Cooprider, Nathan (2016-02-03). "Live Whitelisting!". Threat Stack. Retrieved 20 December 2018.
- ^ "HP-UX Whitelisting". HP. Archived from the original on 21 December 2018. Retrieved 20 December 2018.
- ^ a b Houghton, F., & Houghton, S. (2018). "'Blacklists' and 'whitelists': a salutary warning concerning the prevalence of racist language in discussions of predatory publishing."
- ^ Taylor, Derrick Bryson (2020-07-10). "George Floyd Protests: A Timeline". The New York Times. ISSN 0362-4331. Retrieved 2020-10-14.
- ^ "IP Whitelisting - Documentation". help.gooddata.com. Archived from the original on 2020-09-30. Retrieved 2020-10-14.
- ^ a b Cimpanu, Catalin. "GitHub to replace "master" with alternative term to avoid slavery references". ZDNet. Retrieved 2020-10-14.
- ^ "Code Smell 223 - Racial Naming". Maximiliano Contieri - Software Design. 3 September 2023. Retrieved 2023-09-03.
- ^ "blacklist | Origin and meaning of blacklist by Online Etymology Dictionary". etymonline.com. Retrieved 2020-10-14.
- ^ "What is Little Black Book?". Writing Explained. Retrieved 2020-10-17.
- ^ Grammarian, Angry (22 July 2020). "Is 'master bedroom' a racist term? As language evolves, consider history and usage. | The Angry Grammarian". inquirer.com. Retrieved 2020-10-14.
- ^ Martin, Ben L. (1991). "From Negro to Black to African American: The Power of Names and Naming". Political Science Quarterly. 106 (1): 83–107. doi:10.2307/2152175. ISSN 0032-3195. JSTOR 2152175.
Whitelist
View on GrokipediaFundamentals
Definition and Purpose
A whitelist is a predefined list of approved entities, such as email addresses, IP addresses, domains, or applications, that are explicitly permitted to access resources or bypass restrictions.[1] According to the National Institute of Standards and Technology (NIST), it consists of "A list of discrete entities, such as hosts or applications that are known to be benign and are approved for use within an organization and/or information system."[7] The primary purpose of a whitelist is to enforce a "default deny" policy, under which only explicitly listed items are allowed while all others are blocked by default.[8] This approach enhances security by minimizing the attack surface and reducing exposure to untrusted or malicious elements, in contrast to permissive policies that allow broad access and rely on reactive blocking.[2] It provides fine-grained control over system interactions, simplifying monitoring and compliance efforts in environments where trust must be explicitly verified.[9] Entities attempting access are matched against the whitelist through exact comparisons or pattern-based rules, such as regular expressions applied to domains or paths.[10] Common matching attributes include file names, paths, digital signatures, or cryptographic hashes to verify authenticity.[8] Updates to the list typically require administrative oversight and approval to prevent unauthorized additions that could compromise security.[2] The concept underlying whitelisting evolved from access control lists (ACLs) in early mainframe systems, such as the Multics operating system developed starting in 1965, where ACLs associated permissions directly with resources to control user access.[11]Comparison to Blacklisting
Whitelisting operates as a positive security model, permitting only explicitly approved items or behaviors while denying all others by default, whereas blacklisting employs a negative security model that allows everything except known threats.[3][12] This fundamental distinction makes whitelisting stricter and more comprehensive in controlling access, particularly in high-risk environments where unauthorized elements pose significant threats.[3] A key advantage of whitelisting over blacklisting is its effectiveness against dynamic and unknown threats, such as zero-day attacks, by limiting the attack surface through a default-deny posture that blocks unapproved entities regardless of their novelty.[3][12] In contrast, blacklisting relies on identifying and updating lists of known bad actors, which can fail against novel malware or customized exploits.[3] However, whitelisting demands substantial ongoing maintenance to incorporate legitimate new items, such as software updates or emerging trusted sources, potentially leading to disruptions if not managed diligently; it can also prove overly restrictive in dynamic systems where frequent changes occur.[3][12] Blacklisting, while easier to implement initially, risks higher false negatives by permitting unknown risks to pass through.[3] Whitelisting is best suited for controlled, high-security settings like corporate networks, where the benefits of stringent protection outweigh maintenance costs, whereas blacklisting fits broader, less curated scenarios such as consumer email filtering, allowing greater flexibility at the expense of comprehensive coverage.[3][12] Hybrid approaches often integrate both models for layered defense, using whitelisting as the primary gatekeeper to enforce strict defaults while supplementing with blacklisting to address identified threats efficiently.[3][12]Email Whitelisting
Non-Commercial Implementations
Non-commercial implementations of email whitelisting emphasize open-source tools and community-driven practices, providing accessible options for individuals and small organizations to filter spam by explicitly approving trusted senders. A prominent example is Apache SpamAssassin, an open-source spam detection system that integrates whitelisting via configuration directives in its local.cf file, allowing patterns such as specific email addresses (e.g., [email protected]), domains (e.g., *@isp.com), or wildcards (e.g., *.domain.net) to bypass filtering.[13] The Apache SpamAssassin project further supports community-maintained whitelists through plugins and shared rule sets that users can incorporate to enhance trusted sender recognition.[14] User-managed whitelists in personal email clients offer simple, manual techniques for approving senders. In Mozilla Thunderbird, users configure junk settings to exempt messages from whitelisted address books or create filters that move approved emails to the inbox, effectively bypassing the junk folder.[15] Similarly, Microsoft Outlook enables whitelisting by adding sender email addresses or domains to the Safe Senders list in its Junk Email options, ensuring those messages are not marked as junk.[16] Community resources augment these tools with free, volunteer-curated databases for spam avoidance. DNSWL.org operates as a DNS-based whitelist, listing reputable IP addresses of mail servers to reduce false positives; it is queried in standard DNSBL format (e.g., reversed IP in list.dnswl.org) and integrated into filters like SpamAssassin for automated checks.[17] Other open DNS-based lists, maintained by collaborative efforts, allow server administrators to reference shared whitelists during email processing. Configuring server-side whitelists in open-source MTAs like Postfix involves editing access maps for sender restrictions. In the main.cf file, setsmtpd_sender_restrictions = check_sender_access hash:/etc/postfix/access; then, in the /etc/postfix/access file, define patterns such as user@domain OK for specific addresses, domain.tld OK for domains (matching subdomains if enabled), or @domain.tld OK for all users in a domain, followed by running postmap /etc/postfix/access to compile the database and reloading Postfix.[18]
These approaches, while cost-free and customizable, rely heavily on user expertise for setup and ongoing management, potentially leading to inconsistencies, and feature slower update cycles dependent on community contributions rather than dedicated commercial support.[19]
Commercial Services
Commercial email whitelisting services provide scalable, vendor-supported solutions designed for businesses handling high volumes of email traffic, offering advanced features beyond basic configurations. Major providers include Microsoft Defender for Office 365, which utilizes tenant allow/block lists to permit emails from trusted senders, domains, or IP addresses, ensuring seamless integration within Microsoft 365 ecosystems.[20] Proofpoint Essentials employs domain-based allowlisting through its Safe Sender lists, enabling organizations to bypass spam and malware checks for verified sources while maintaining robust threat detection.[21] Mimecast offers targeted whitelisting via Permitted Senders policies, allowing administrators to approve specific senders for bypassing security scans, particularly useful for verified business partners.[22] These services emphasize automation and integration to enhance efficiency for enterprise environments. Automated updates ensure whitelists remain current without manual intervention, while API integrations—such as Proofpoint's sender list API, Mimecast's permit-or-block-sender endpoint, and Microsoft’s Exchange Online PowerShell for tenant lists—facilitate dynamic management of allowlists from external systems.[23][24][20] Analytics features provide insights into whitelist efficacy, including reports on allowed versus blocked emails and false positive rates, helping administrators refine policies; for instance, Proofpoint's dashboards track sender compliance and threat evasion attempts. In enterprise use cases, these solutions integrate with Security Information and Event Management (SIEM) systems to support compliance requirements like GDPR, where whitelisting ensures controlled email flows for data protection audits.[25][26] Cost models typically range from $2 to $5 per user per month as of 2025, depending on the plan and provider; Microsoft Defender Plan 1 starts at $2 per user/month, Proofpoint Essentials Business edition at approximately $3 per user/month, and Mimecast's basic email security is quote-based but typically around $3–$4 per user per month.[27][28] The evolution of commercial email whitelisting accelerated post-2010 with the rise of cloud-based email platforms like Microsoft Office 365, launched in 2011, driving demand for integrated security services to manage increased volumes and sophisticated threats.[29] By the mid-2010s, providers incorporated AI-assisted management to automate whitelist curation and detect anomalies in sender patterns, reducing administrative overhead amid growing phishing attempts.[29] In the finance sector, adoption has been prominent for securing vendor communications; for example, a major U.S. financial institution implemented Proofpoint Email Protection, blocking over 6.6 million unwanted messages in 30 days and achieving 100% rejection of fraudulent emails, supporting regulatory compliance and operational continuity.[30]Content and Advertising Whitelisting
Advertising Whitelists
In digital advertising, whitelists refer to curated lists of approved ad networks, domains, creative formats, or publishers that are permitted to serve advertisements, often bypassing restrictions imposed by ad blockers or platform policies. These lists enable selective ad delivery to maintain user experience while allowing certain non-intrusive ads to appear. For instance, ad blockers like AdBlock Plus use whitelists to permit ads that meet specific criteria, ensuring they do not disrupt content viewing.[31][32] A primary mechanism for advertising whitelists is the Acceptable Ads initiative by eyeo GmbH, the company behind AdBlock Plus, which integrates crowdsourced input from users and third-party contributors alongside oversight by the independent Acceptable Ads Committee. Ads are evaluated against standards for unobtrusiveness, such as size limits (e.g., no more than 200 pixels high above primary content) and clear labeling as advertisements, with proposals for inclusion publicly reviewed before whitelisting. This process audits for compliance, excluding intrusive formats like pop-ups or autoplay videos, and allows approximately 90% of participants to join without fees. Industry standards further support whitelist creation, including the Interactive Advertising Bureau's (IAB) LEAN principles (Light, Encrypted, AdChoices-supported, Non-invasive), which guide publishers in developing lightweight ads to reduce blocking incentives, and Google's Ads.txt framework, which verifies authorized sellers on publisher domains to build trust in ad supply chains.[33][34][35] Whitelisting benefits publishers by recovering lost revenue from ad-blocking users—estimated at $54 billion as of 2024 industry-wide—while preserving user privacy through non-tracking, relevant ads that enhance site sustainability.[36] However, controversies arise from potential abuse, as large advertisers may disproportionately influence whitelists via payments to ad blocker operators (e.g., eyeo's undisclosed fees for some inclusions), raising concerns about fairness and enabling problematic content exposure, with studies showing privacy-focused users encountering 13.6% more problematic ads via "acceptable" exceptions.[37][38] Implementation often occurs publisher-side through ad servers like Google Ad Manager (formerly DoubleClick), where whitelists restrict ad placements to approved domains or networks, minimizing fraud and ensuring compliance. For example, integrating Ads.txt with ad servers verifies seller authorization, boosting fill rates and reducing unauthorized impressions.[39]Web Content Whitelists
Web content whitelists enable users to bypass default restrictions in browsers and security software, granting access only to pre-approved URLs deemed safe for browsing. In web browsers such as Google Chrome, administrators can configure URL allowlists through enterprise policies to permit specific sites while blocking others, ensuring controlled access in educational or organizational environments.[40] Similarly, security software like Norton Safe Web allows users to add website exclusions via browser protection settings, effectively whitelisting trusted URLs to avoid false positives in threat detection.[41] Parental control applications, such as Qustodio, provide customizable web filtering rules where parents can create personal allowlists of websites, overriding category-based blocks to suit family needs.[42] In enterprise settings, proxy servers like Blue Coat ProxySG (now part of Broadcom) support whitelisting approved web domains through content policy language, allowing granular control over HTTP/HTTPS traffic to vetted sites.[43] These tools often integrate cloud-based synchronization to propagate whitelist updates across devices in real time, maintaining consistency without manual intervention on each endpoint.[44] Inclusion on web content whitelists typically relies on safety evaluations from services like Google Safe Browsing, which flags and excludes sites associated with malware distribution, phishing attempts, or social engineering scams.[45] Sites must demonstrate absence of harmful content, such as deceptive redirects or exploit kits, to qualify as safe and eligible for whitelisting in integrated browser protections.[46] Implementing web content whitelists presents challenges in balancing user usability with robust security, particularly when handling dynamic content on websites that frequently update or generate pages algorithmically, complicating static URL assessments.[47] Maintaining accurate whitelists requires ongoing database updates to account for evolving web threats and site changes, often mitigated through cloud-synced policies but risking over-restriction if not carefully managed.[47]Network and Security Whitelisting
IP Address Whitelisting
IP address whitelisting involves configuring network firewalls to permit traffic solely from predefined IP addresses or ranges, thereby restricting access to authorized sources. In Linux systems, this is commonly achieved using iptables, where rules are added to the INPUT chain to accept packets from specified sources before a default DROP policy blocks others. For instance, a rule might allow incoming traffic on port 22 for SSH from a single IP with the commandiptables -A INPUT -s 192.168.1.100 -p tcp --dport 22 -j ACCEPT, followed by ensuring the chain policy drops unmatched traffic.[48][49] To handle ranges efficiently, Classless Inter-Domain Routing (CIDR) notation is employed, such as 192.168.1.0/24 to whitelist an entire subnet, reducing rule complexity and improving performance.[50][51] This approach ensures only trusted traffic traverses the firewall, with rules evaluated in sequence until a match occurs.[48]
Common applications of IP whitelisting include securing remote access protocols like SSH, where firewall rules limit connections to trusted administrator IPs, preventing brute-force attacks from external sources. In cloud environments, AWS Security Groups function as virtual firewalls, allowing inbound rules to whitelist specific CIDR blocks for services such as EC2 instances, ensuring API endpoints and databases are accessible only from approved networks.[52][53] Similarly, VPN gateways often incorporate IP whitelisting to validate client connections, restricting tunnel access to predefined IP ranges and enhancing secure remote workforce connectivity.[54][55]
Various tools facilitate IP whitelisting implementation. Commercial solutions like Cisco ASA use access control lists (ACLs) to define permitted IPs, where commands such as access-list whitelist extended permit ip host 192.168.1.100 any add entries to allow traffic from specific addresses before applying the list to interfaces.[56] Open-source platforms like pfSense enable whitelisting through its web-based GUI, where firewall rules specify source IPs or aliases containing CIDR ranges (e.g., 192.168.1.0/24) and set the action to "Pass" for targeted interfaces.[57][58] For dynamic scenarios, such as temporary vendor access with changing IPs, scripts can automate updates; for example, Bash scripts resolve hostnames to IPs via DNS and insert iptables rules, often integrated with cron jobs for periodic refreshes.[59][60]
From a security perspective, IP whitelisting effectively prevents unauthorized remote access by blocking traffic from unlisted sources, significantly reducing the attack surface against threats like distributed denial-of-service (DDoS) and unauthorized intrusions. However, it carries risks such as IP spoofing, where attackers forge source addresses to bypass restrictions, potentially leading to data breaches if not addressed. Mitigations include layering defenses like multi-factor authentication (MFA) and intrusion detection systems (IDS), which validate traffic beyond IP origins.[61][62][63]
Best practices for IP whitelisting emphasize regular audits to review and prune outdated entries, ensuring the list remains minimal and relevant to avoid over-permissive access. Integration with geolocation data enhances this by dynamically restricting whitelists to specific regions, combining IP ranges with databases like MaxMind GeoIP for automated regional filtering. Organizations should also employ least-privilege principles, documenting changes and testing rules to maintain efficacy without disrupting legitimate traffic.[64][65][66]
