SURBL (no longer an acronym (previously stood for 'Spam URI RBL')) is a collection of URI DNSBL lists of Uniform Resource Identifier (URI) hosts, typically web site domains, that appear in unsolicited messages. SURBL can be used to search incoming e-mail message bodies for spam payload links to help evaluate whether the messages are unsolicited. For example, if http://www.buypillswithoutprescription.com is blacklisted, then e-mail messages with a message body containing this URI may be classified as unsolicited. URI DNSBLs differ from prior DNSBLs, which commonly list mail sending IP addresses. SURBL is a specific instance of the general URI DNSBL list type.
SURBL provides several different lists from different sources:
- JP jwSpamSpy and Prolocation sites
- WS SA blacklist web sites
- AB AbuseButler web sites
- OB Outblaze URI blacklist
- SC SpamCop reported sites
- PH phishing, malware and abused sites
All lists are gathered into multi.surbl.org.
A DNS query of a domain or IP address taken from a URI can be sent in the form of spamdomain.example.multi.surbl.org or 18.104.22.168.multi.surbl.org. The multi DNS zone return records contain codes that indicate which blacklist contains the queried for domain or IP address. Many spam filters support use of SURBL. Small sites can use SURBL through public DNS, an rsync data feed is available to professional users.
SURBL was created in 2004 to replace formatted text-based lists such as WS that were previously used in SpamAssassin and distributed through web sites. The announcement of SURBL as a URI DNSBL was made April 8, 2004 to the SpamAssassin user community. SURBL is the first major list of the URI DNSBL type, later followed by uribl.com, IvmURI and Spamhaus DBL.
- DNSBL, a spam prevention method in which e-mail messages are accepted or rejected depending on the IP address of the mail server from which the message is received.