[ Thanks to jhansonxi for this link.
]
“I reduced the DansGuardian user account and blacklist
maintenance hassles with my previous two utilities but while
working on whitelisting I found the need for a few more.“In DansGuardian (DG) terms a blacklist bans something, a
greylist allows something (overrides blacklisting) but still
filters it, and an exceptionlist allows something without filtering
(overriding greylists and blacklists). The “something” can be URLs,
IP addresses, server names, etc., depending upon the specific list
type. Blacklisting a site is easy but blacklisting a specific type
of content is very difficult and error-prone. It works the same way
as anti-malware utility definitions – if the undesirable items are
on the list, and they match a particular requested target, then
it’s blocked. If not, then it gets through. It’s a big Internet out
there and trying to block all the bad is rather difficult. “Bad” is
also relative and what is bad for one person/religious
group/company/government may not be bad for another. Whitelisting
has the opposite problems in that you gain strict control over what
is available but trying to predict where the user wants to go,
determining if that is a safe destination, and maintaining the
lists is also difficult.“I found that I needed to use both blacklisting and
whitelisting.”