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150 Chapter 3 • Communication Security: Remote Access and Messaging

Another common reason why a computer with antivirus software can be
infected with viruses is because the signature files have not been updated.Antivirus
software manufacturers release new signature files regularly, and it is up to users to
download and update them.To make this simple, many manufacturers provide fea-
tures to automatically update the signature files via Internet.

Zero Day Attacks
It might be observed that most viruses originate overseas. Typically, this
Head of the Class... update for their product that is “aware” of the threat and can detect its
provides antivirus vendors an opportunity to scramble and produce an

presence in an e-mail or system. However, regardless of how diligent an
administrator is in the automation and updating of antivirus software,
some viruses are released into the user community before antivirus ven-
dors can respond with a protective solutions. This is called a Zero Day
Attack, because the virus has not been propagating for even a day.
In this situation, the signature of the file/attachment can be used to
create rules on e-mail systems and directory servers (Group Policy, in
Active Directory) to block the utilization of a file with that signature. Of
course, this requires that you first get the signature of the file.

Spam

Spam is unsolicited bulk e-mail (UBE), much like the advertisements and other
junk e-mail that frequently fills home mailboxes. Spam is junk e-mail that rarely is
of any interest to users, is never requested, and is sent by people you do not know.
The origin of the name is ambiguous at best and goes back to the early days of
the Internet and Bulletin Board Systems (BBSes) run on individual computers to
which people dialed in directly. Some believe it came from computer users at the
University of California who made a derogatory comparison between the pro-
cessed lunchmeat product made by Hormel and e-mail that nobody wants. Others
believe the term comes from the song by British comedy group Monty Python,
which was about the ubiquity of spam.Whatever the exact source, spam is some-
thing that is not likely to disappear from the Internet anytime soon.
Spam often comes from lists of e-mail addresses or software that sends thou-
sands or millions of messages. Many legitimate businesses avoid soliciting customers
this way, because people do not like receiving spam.Also, many ISPs specify that
bulk e-mail is a violation of the contract between themselves and their customers,
so they can shut down sites or disable the accounts of customers who send spam.

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