A computer worm is a program
which copies
itself across a network.
A computer worm differs from
a computer
virus in that a computer worm can
run itself. A
virus
needs a host program to run,
and the virus
code runs as part of the host program. A
computer worm can spread
without a host
program, although some
modern computer
worms also use files to hide inside.
Well known examples of the
computer worm
The original computer worm
was (perhaps
accidentally) unleashed on the Internet by
Robert Tappan Morris in 1988.
TheInternet
Worm used send mail, fingerd,
and rsh/rexec
to spread itself across the
Internet.
The SQL Slammer Worm of 2003
used a
vulnerability in Microsoft SQL
Server 2000 to spread itself across the
Internet. The Blaster
Worm, also of 2003, used a
vulnerability in
Microsoft DCOM RPC to spread
itself. The Melissa worm of 1999, the
Sobig worms
of
2003 and the Mydoom worm of
2004 all
spread through e-mail. These worms
shared some
features of a trojan horse , in
that they spread
by enticing a user to open an
infected e-mail attachment.
Mydoom also attempted to
spread itself
through
thepeer-to-peer file
sharingapplicat ion KaZaA.
The Mydoom worms attempted
aDenial of
Service (DoS) attackagainst SCO
and
Microsoft.Prote cting yourself against
computer
worms
Computer worms which spread
through
vulnerabilities in network services can best
be
protected against by keeping
up-to-date in
installing patches provided by
operating system
and application vendors. This
includes worms
like SQL Slammer and Blaster.
Computer worms which spread
like trojan horses can best be defended
against by not
opening attachments in your e-
mail. These
infected attachments are not
limited to .EXE files. Microsoft Word and Excel
files can
contain
macros which spread infection.