Composite Blocking List

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.
• Misconfigured mail servers (for example, servers that send HELO with 'localhost' or a similar incorrect domain.)

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.

See also

• Comparison of DNS blacklists
• CBL Index - estimate of outgoing spam reputation

External links

• The CBL
• CBL lookup and removal page