Spam is flooding the Internet with many copies of the same message, in
an attempt to force the message on people who would not otherwise choose
to receive it. Most spam is commercial advertising, often for dubious
products, get-rich-quick schemes, or quasi-legal services. Spam costs the
sender very little to send -- most of the costs are paid for by the
recipient or the carriers rather than by the sender.
There are two main types of spam, and they have different effects on
Internet users. Cancellable Usenet spam is a single message sent to 20 or
more Usenet newsgroups. (Through long experience, Usenet users have found
that any message posted to so many newsgroups is often not relevant to
most or all of them.) Usenet spam is aimed at "lurkers", people
who read newsgroups but rarely or never post and give their address away.
Usenet spam robs users of the utility of the newsgroups by overwhelming
them with a barrage of advertising or other irrelevant posts. Furthermore,
Usenet spam subverts the ability of system administrators and owners to
manage the topics they accept on their systems.
Email spam targets individual users with direct mail messages. Email
spam lists are often created by scanning Usenet postings, stealing
Internet mailing lists, or searching the Web for addresses. Email spams
typically cost users money out-of-pocket to receive. Many people - anyone
with measured phone service - read or receive their mail while the meter
is running, so to speak. Spam costs them additional money. On top of that,
it costs money for ISPs and online services to transmit spam, and these
costs are transmitted directly to subscribers.
One particularly nasty variant of email spam is sending spam to mailing
lists (public or private email discussion forums.) Because many mailing
lists limit activity to their subscribers, spammers will use automated
tools to subscribe to as many mailing lists as possible, so that they can
grab the lists of addresses, or use the mailing list as a direct target
for their attacks.
(For more information about the origin of the term "spam",
and the formal definitions of Usenet spam, see J.D.Falk's excellent Net
Abuse FAQ)
