The Spam and Open Relay Blocking System
The SORBS (Spam and Open Relay Blocking System) provides free access to its DNS-based Block List (DNSBL) to effectively block email from more than 12 million host servers known to disseminate spam, phishing attacks and other forms of malicious email. The list typically includes email servers suspected of sending or relaying spam, servers that have been hacked and hijacked, and those with Trojan infestations. In an attempt to provide preemptive protection, SORBS also lists servers with dynamically allocated IP addresses. SORBS maintains 17 distinct DNSBL zones.
Much like recent.dnsbl.sorbs.net, hosts listed in old.dnsbl.sorbs.net have been seen sending spam within the last year. This blacklist contains all data that is active in recent.dnsbl.sorbs.net and new.dnsbl.sorbs.net. old.dnsbl.sorbs.net is the final step in which a host could potentially still make an effort to be delisted. With the threshold being one year, the chances are unlikely, and more likely that this host will remain permanently listed within SORBS.