Composite Blocking List
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In computer networking, the Composite Blocking List (CBL) is a DNS-based Blackhole List of suspected E-mail spam senders.
The CBL takes its source data from very large spamtraps/mail infrastructures, and only lists IPs exhibiting characteristics such as:
- Open proxies of various sorts (HTTP, socks, AnalogX, wingate etc)
- Worms/viruses that do their own direct mail transmission
- Trojan horse or "stealth" spamware, without doing open proxy tests of any kind.
Entries automatically expire after a period of time.
The CBL does not provide public access to gathered evidence.
CBL data are used in Spamhaus XBL list.