The SURBL Multi Blacklist is a composite blocklist (blacklist) that aggregates multiple data sources and uses a unique bitmasking system to identify IPs or domains involved in various forms of online abuse.
The SURBL Multi Blacklist is a consolidated feed of all SURBL's public data sources combined into a single, efficient blacklist. This blocklist is not a single list but a combination of several specialized lists, making it a powerful tool for identifying malicious or unwanted content sources. Its policy is to flag domains and IPs associated with unsolicited messages, phishing, malware, and other abuse.
Technically, it uses a system called bitmasking. This means a single DNS query can reveal which specific sub-lists a domain or IP appears on. The response is an IP address, like 127.0.0.X, where 'X' is a number that indicates list membership. For example, a value of 8 means the entry is on the phishing (PH) list, while a value of 64 indicates it's on the ABUSE list. If an entry is on multiple blacklists, these values are added together. A value of 80 (16 + 64) would mean the entry is on both the MW and ABUSE lists. This makes the SURBL Multi Blacklist a highly detailed and dynamic blacklist or blocklist, with data updated on average every 30 to 40 seconds.
The SURBL Multi Blacklist is operated by SURBL BV, a corporation registered in the Netherlands. The company specializes in providing near real-time reputation data feeds. This data is used by a wide range of organizations to secure email systems, web access through DNS firewalls, mobile communications, and other digital activities. The name SURBL originally stood for 'SpamCop Uri Realtime Block List' but was later updated to 'Spam Uri Realtime Block List' as the project expanded to include data from more sources.
To request removal from this blocklist, you must first use the official lookup tool on the SURBL website. You can find the removal form by visiting the SURBL Lookup page and following the instructions provided. Before you request to be delisted from this blacklist, it is critical to resolve the underlying issue that caused the listing.
Once you have taken corrective action, you can proceed with the removal request. Submitting a delisting request without fixing the problem will likely result in the request being denied.
The impact of being listed on the SURBL Multi Blacklist is considered medium. Because it is a composite blocklist used not only for email filtering but also for DNS firewalls and other security applications, a listing can have varied effects. Your email deliverability will likely suffer, with messages being blocked or sent to the spam folder by providers that use this blacklist. Beyond email, you may find that users are blocked from accessing your website if their network uses a DNS firewall that incorporates SURBL data. The specific impact depends on which of the sub-lists you are on and how the receiving system is configured to use the data from the blacklist.
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