spamd is an ISC-licensed lightweight

spam Spam may refer to: * Spam (food), a canned pork meat product * Spamming, unsolicited or undesired electronic messages ** Email spam, unsolicited, undesired, or illegal email messages ** Messaging spam, spam targeting users of instant messaging ( ...

-deferral daemon written under the umbrella of the

OpenBSD OpenBSD is a security-focused, free and open-source, Unix-like operating system based on the Berkeley Software Distribution (BSD). Theo de Raadt created OpenBSD in 1995 by forking NetBSD 1.0. According to the website, the OpenBSD project em ...

project. spamd works directly with smtp connections, and supports features such as greylisting, minimising

false positives A false positive is an error in binary classification in which a test result incorrectly indicates the presence of a condition (such as a disease when the disease is not present), while a false negative is the opposite error, where the test result ...

compared to a system that does full-body analysis. spamd is designed to work in conjunction with pf(4), and should be fully functional on any POSIX system where pf is available, i.e.

NetBSD NetBSD is a free and open-source Unix operating system based on the Berkeley Software Distribution (BSD). It was the first open-source BSD descendant officially released after 386BSD was forked. It continues to be actively developed and is a ...

FreeBSD FreeBSD is a free and open-source Unix-like operating system descended from the Berkeley Software Distribution (BSD), which was based on Research Unix. The first version of FreeBSD was released in 1993. In 2005, FreeBSD was the most popular ...

and DragonFly BSD.

Uses and features

Spamd is most useful in preventing inbound spam from reaching

mail servers Within the Internet email system, a message transfer agent (MTA), or mail transfer agent, or mail relay is software that transfers electronic mail messages from one computer to another using SMTP. The terms mail server, mail exchanger, and MX host ...

. It can also be used as a partial

application Application may refer to: Mathematics and computing * Application software, computer software designed to help the user to perform specific tasks ** Application layer, an abstraction layer that specifies protocols and interface methods used in a c ...

level proxy to ensure that external mail servers connecting to internal mail servers behave legitimately. Additionally, spamd can be very useful in preventing outgoing spam from systems that may be compromised or under the control of spammers. It can be used to block spammers with the use of the following features: *

Blacklisting Blacklisting is the action of a group or authority compiling a blacklist (or black list) of people, countries or other entities to be avoided or distrusted as being deemed unacceptable to those making the list. If someone is on a blacklist, t ...

: such as the

SPEWS The Spam Prevention Early Warning System (SPEWS) was an anonymous service that maintained a list of IP address ranges belonging to internet service providers (ISPs) that host spammers and show little action to prevent their abuse of other network ...

database or other lists of IPs, and features including small windows sizes. * Tarpitting: this can slow down spam reception considerably and hold connections open for a significant amount of time. * Greylisting: this forces email to be delayed for a configurable period, requiring the remote end to resend mail at least once in order for it to be delivered. * SpamTrapping / GreyTrapping: this is the seeding of an email address so that spammers can find it, but normal users can not. If the email address is used then the sender must be a spammer and they are black listed.

External links

*
Article: Annoying spammers with pf and spamd

Article: Don't run a mail server? Here's how you can still hurt spammers from your home PC.
(With video)

(from the original author)

OpenBSD BSD software Unix network-related software OpenBSD software using the ISC license {{Free-software-stub

Uses and features

See also

External links