Summary
The Spamhaus Content Hash Blocklist (HBL) is a real-time database of hashes of unsolicited bulk email content, effectively identifying and blocking spam based on message content, even from non-blacklisted IPs. It complements the Spamhaus Block List (SBL), which lists IP addresses. Unlike DCC (Distributed Checksum Clearinghouse), which identifies bulk email using checksums of message bodies without considering malicious intent, the HBL focuses on content. Vipul's Razor is a collaborative system relying on user reports and checksums, making it susceptible to manipulation. Cloudmark employs fingerprinting technology, analyzing message content, structure, and sending patterns, adapting to new spam techniques with global threat intelligence. Spamhaus also uses content matching and maintains a reputation system for persistent spam detection. Checking against blocklists like Spamhaus is crucial for email deliverability. The Razor database is used by Cloudmark.
Key findings
- Spamhaus HBL Effectiveness: Effective at blocking spam based on content, even from legitimate IPs; complements IP-based blocklists.
- DCC Focus: Identifies bulk email based on checksums, without considering malicious intent.
- Vipul's Razor Reliance: Relies on user reports, making it susceptible to manipulation and bias.
- Cloudmark Adaptability: Uses fingerprinting to adapt to new spam techniques and identify variations of known spam.
- Spamhaus Versatility: Employs content matching and reputation systems for persistent spam detection.
- Blocklist Importance: Checking against blocklists like Spamhaus is crucial for ensuring email deliverability.
Key considerations
- DCC Accuracy: Can sometimes flag legitimate bulk email as spam.
- Vipul's Razor Vulnerability: Susceptible to manipulation if a small group misreports legitimate messages.
- Spamhaus Reputation: Spamhaus is regarded as a highly effective and commonly used blocklist.
- Cloudmark Integration: Cloudmark uses The Razor database for enhanced functionality.
What email marketers say
9 marketer opinions
The Spamhaus Content Hash Blocklist (HBL) focuses on identifying spam based on message content, using hashes to detect known spam even from non-blacklisted IPs. DCC (Distributed Checksum Clearinghouse) identifies bulk email through checksums of message bodies, primarily detecting mass mailings. Vipul's Razor relies on user reports to identify spam. Cloudmark employs fingerprinting technology to analyze message content, structure, and sending patterns, incorporating global threat intelligence to adapt to new spam techniques. Accuracy and effectiveness vary, with DCC potentially flagging legitimate bulk email and Vipul's Razor susceptible to manipulation. Spamhaus is considered an effective blocklist, and checking against such lists is crucial for email deliverability.
Key opinions
- Spamhaus HBL: Identifies spam based on message content hashes, blocking spam even from IPs not on traditional blocklists; complements IP-based lists.
- DCC: Detects bulk email based on message body checksums, focusing on mass mailings rather than content analysis.
- Vipul's Razor: Relies heavily on user reports for spam identification, making it vulnerable to manipulation.
- Cloudmark: Uses fingerprinting to analyze message content and patterns, adapting to new spam techniques with global threat intelligence.
- Effectiveness: Spamhaus is a widely regarded and effective blocklist for identifying and blocking spam.
Key considerations
- DCC Accuracy: DCC may sometimes incorrectly flag legitimate bulk email due to similarities with known spam.
- Vipul's Razor Bias: Vipul's Razor can be susceptible to manipulation if a small group intentionally misreports legitimate messages.
- Deliverability: Checking against blocklists like Spamhaus is crucial for improving email deliverability.
- Adaptability: Cloudmark's strength lies in its ability to adapt to new spam techniques through fingerprinting.
Marketer view
Email marketer from Reddit answers that Vipul's Razor relies heavily on user reports, making it susceptible to manipulation or bias if a small group of users intentionally misreports legitimate messages as spam. <https://www.reddit.com/>
25 Feb 2024 - Reddit
Marketer view
Email marketer from EmailSecurityPsm explains that Cloudmark's strength lies in its ability to adapt to new spam techniques through its fingerprinting technology. It is designed to recognize variations of known spam messages. <https://emailsecuritypsm.com/email-security-vendors/>
31 Jan 2022 - EmailSecurityPsm
What the experts say
7 expert opinions
Spamhaus's content hash blocklist (HBL) is highly effective at identifying spam by analyzing message content, blocking even messages from IPs not traditionally blacklisted, and particularly targeting phishing and malware links. While DCC is primarily a bulk email filter without a reputation component, Spamhaus's HBL is suggested to be closer to Vipul's Razor (user-feedback centric) and Cloudmark (fingerprinting), with potential for evolving into a full BEC/anti-spam solution. Spamhaus also uses content matching. The Razor database, created by Vipul Ved Prakash and Jordan Ritter, is used by Cloudmark. Spamhaus also maintains a reputation system allowing for the detection of spam even when the content changes.
Key opinions
- Spamhaus HBL Effectiveness: Content hash blocklist is highly effective post-acceptance, especially against phishing/malware.
- DCC Limitations: DCC lacks a reputation component, functioning merely as a bulk/not bulk filter.
- Spamhaus HBL Comparison: HBL closer to Vipul's Razor (user-feedback) and Cloudmark (fingerprinting) than DCC; potential evolution into BEC solution.
- Content Matching: Spamhaus uses content matching to identify spam from IPs not traditionally blacklisted.
- Reputation System: Spamhaus has a reputation system that enables it to detect spam over time, even when content changes
Key considerations
- DCC Scope: DCC primarily identifies bulk mail, not inherently malicious content.
- HBL Discrete Hammer: Spamhaus is a much more discrete hammer, due to its content matching capabilities.
- Cloudmark Influence: Cloudmark uses The Razor database which provides it with some functionality.
Expert view
Expert from Email Geeks shares that Spamhaus has a content hash blocklist which is incredibly effective after mail has been accepted.
21 Apr 2025 - Email Geeks
Expert view
Expert from Email Geeks shares that The Razor database by Vipul Ved Prakash and Jordan Ritter allow Unix clients to work out of the same database used by the commercial customers of the Cloudmark system.
6 May 2023 - Email Geeks
What the documentation says
5 technical articles
The Spamhaus HBL (Hash Blocklist) is a real-time database of unsolicited bulk email content, identifying and blocking spam based on content hashes, even from non-blacklisted IPs. It differs from the Spamhaus SBL (Spamhaus Block List), which lists IP addresses of known spam sources. Vipul's Razor is a collaborative spam detection network that combines user reports and checksums, emphasizing user feedback. Cloudmark uses fingerprinting technology, creating unique message signatures based on content, structure, and sending patterns for accurate spam identification. DCC (Distributed Checksum Clearinghouse) identifies bulk email by computing checksums of message bodies and comparing them to a central database, focusing on mass mailings rather than malicious content.
Key findings
- Spamhaus HBL: Real-time database of spam content hashes; blocks spam even from legitimate IPs.
- Spamhaus HBL vs SBL: HBL lists content hashes; SBL lists IP addresses.
- Vipul's Razor: Collaborative; combines user reports and checksums; emphasizes user feedback.
- Cloudmark: Uses fingerprinting technology to create unique message signatures; allows identification of slightly modified spam.
- DCC: Identifies bulk email by checksums; detects mass mailings, not malicious intent.
Key considerations
- Content vs Source: Spamhaus HBL focuses on content; Spamhaus SBL focuses on the source IP.
- User Feedback: Vipul's Razor relies heavily on user feedback, potentially introducing bias.
- Fingerprinting Accuracy: Cloudmark's fingerprinting aims for accurate spam identification even with slight modifications.
- Bulk vs Malicious: DCC primarily identifies bulk email, not necessarily malicious content.
Technical article
Documentation from Spamhaus explains the HBL lists hashes of known spam content, whereas the SBL (Spamhaus Block List) lists IP addresses of known spam sources. The HBL can block spam even from legitimate IPs if the content matches known spam hashes. <https://www.spamhaus.com/>
3 Mar 2023 - Spamhaus
Technical article
Documentation from Apache SpamAssassin Wiki explains Vipul's Razor is a distributed, collaborative, spam detection and filtering network. It uses a combination of user reports and checksums to identify spam. It emphasizes user feedback as a primary component, differentiating it from purely content-based systems. <https://cwiki.apache.org/confluence/display/SPAMASSASSIN/UsingRazor>
8 Nov 2024 - Apache SpamAssassin Wiki
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