Spam_BLIP

Spam BLIP stops comment and ping spam from being posted, primarily by
checking the IP address attempting to post a comment in one or more
of the public DNS blacklists. A number of options are available
to refine the check, and with the option defaults, a DNS lookup
is only performed the first time an address attempts to post a
comment; thereafter, the address might quickly ‘pass’ because it
was not listed, or quickly be rejected because it was listed.
Spam BLIP creates, and maintains, a database table for this purpose,
and database lookups are quite fast. Therefore, concerns about
DNS lookup time can be limited to an initial comment attempt.

Here are some features of Spam BLIP to consider if you are
not yet falling over yourself to get it installed:

• When WordPress is producing a page for a visitor, it checks
  whether comments are open for each post, and it allows plugins
  to “filter” the check. Spam BLIP uses that filter, but does not
  do DNS lookups at this stage, because DNS lookups can take
  perceptible time. Spam BLIP does check optional user-set
  black and white lists, and optionally existing comments that
  are marked as spam, and of course Spam BLIP’s own database records.
  Those checks are fast, so they should not have a perceptible
  effect on page loading. Furthermore, on pages with multiple
  posts, WordPress runs the filter for each, but Spam BLIP
  stores the first result, so even the fast checks are not
  repeated.

• When a comment is actually submitted, Spam BLIP does the above
  checks, then the DNS lookup only if necessary. At this stage,
  if the DNS lookup causes a perceptible delay, a real human
  (or very clever pet) making the comment should perceive it
  as mere server-side processing. As for spammer robots . . .
  let them wait.

• Spam BLIP comes configured with blacklist domains that have
  worked well during development, so a user should not need to
  be concerned with the blacklists, but there is an advanced
  option to add or delete, activate or disable (yet save)
  list domains, and configure the interpretation of a return
  from a successful lookup.

• Spam BLIP provides user-set whitelist and blacklist options.

• Spam BLIP provides options to check for pings/trackbacks, and
  for user registrations. (The option to blacklist-check user
  registration is off by default. See “Tips” under the help
  tab on the Spam BLIP settings page.)

• Spam BLIP provides options to configure a ‘Time To Live’ (TTL)
  for its database records, and a maximum number of records.
  The TTL is important because, generally, an IP address should
  not be marked permanently. Consider an ISP that quickly
  disables any account that is found to be spamming. An honest
  ISP is also a victim of spammer abuse, and will need to reuse
  addresses. DNS blacklist operators provide means for IP
  address owners to get records removed — Spam BLIP provides
  a configurable TTL for its records. (Database table maintenance
  is triggered approximately hourly by a WordPress cron event.)

• Spam BLIP will optionally check if a commenter address is a
  TOR exit node. TOR (The Onion Router) is an important protection
  for people who need or wish for anonymity. You may want to
  accept comments from TOR users (you should), but unfortunately
  spammers have exploited and abused TOR, which has led some
  DNS blacklist operators to include TOR exit node addresses
  whether or not it is known that the address is spamming. If you
  enable this option (you should), it might let some spam get
  through. In this case, mark the comment as spam, and use the
  Spam BLIP option to check existing comments marked as spam; or
  use Spam BLIP in concert with another sort of spam filter, such
  as one that analyzes comment content. (Please report any
  conflict with other, non-DNS blacklist type spam plugins.
  Note that Spam BLIP is not expected to work in concert with
  other DNS-type anti-spam plugins.)

• Spam BLIP includes a widget that will show options and records
  information. The widget might or might not be an enhancement
  to your page, but in any case it should provide feedback
  while you evaluate Spam BLIP, so it might be used temporarily.