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Real-time blackhole list (RBL) is a dynamic list of IP address owners that are active spammers or spam sources. The RBL may include Internet service providers (ISP) with customers that are known spammers or ISP servers that are hijacked for spamming purposes.
RBL is also known as a DNS Black List (DNSBL).
The majority of spam is the result of online advertisements and unsolicited bulk email (UBE). When spam is delivered, the forwarding IP address is added to the RBL.
The RBL prevents system abuse by halting spam. However, the blacklisting process must be handled carefully. It cannot prohibit appropriate or authentic source connections or open-source networking. If an ISP subscribes to the RBL, the ISP may determine which IP addresses should be blocked and added to the RBL. If an IP address matches an IP address listed on the RBL, the connection is automatically dropped.
The RBL was first implemented by the Mail Abuse Prevention System (MAPS), which was acquired by Trend Micro in 2005. Trend Micro adheres to strict guidelines and policies in its continuous effort to nominate and remove spam IP addresses from its blackhole data listings.