Information Technology Reference
In-Depth Information
Why is e-mail susceptible to viruses and worms?
As you may know,
spam
(in the context of email over the
Internet) is sometimes defined as the sending of unsolicited email to
others—often on a massive scale. In recent years, the volume of
spam messages has ballooned. Here are a few statistics:
On June 16, 2003, the
Seattle Times
reported that America
Online stated it was blocking 2.4 billion spam emails
every
day.
MessageLabs, an Internet filtering firm, estimated that 55%
of all emails sent in May 2003 were unsolicited messages—
up from 40% just the previous month.
In a court case filed by Earthlink against Buffalo Spammer,
the spammer sent some 825 million messages to Earthlink ISP
customers and cost Earthlink $1 million just in terms of
bandwidth.
Altogether, the generation of unsolicited messages or spam has
grown in huge proportions in just a few years. What is it about
email that makes spam the incredibly popular form of advertising
that it is? Most notably, email involves only a few pieces of infor
mation: a sender's address, a receiver's address, a subject, and a text
body, and not all of these are actually required. Of these, the only
essential item is the receiver's address, so mailers will know where
to send the message. With access to lists of email addresses, pro
grams have little difficulty putting the pieces together to generate
email; thus, the only challenge facing mass email programs is de
termining potential addresses. Once those lists are established, spam
can be distributed in huge quantities quickly and at low cost.
To gain addresses, spammers utilize at least four approaches:
Scanning Web Sites: We have already noted that search en
gines often utilize programs to follow links on the Web to browse
sites and collect pages for indexing. Much the same approach can
be used to search the Web for email addresses; programs can fol
low links throughout the Web, but store only email addresses
rather than full pages. This suggests that any email address you
post on a Web site has the potential to be identified and used as
the target of spam.
