Malware can be loosely defined as a malicious computer executable.
The definition requires some flexibility because the term can
describe a wide variety of different types of unwanted programs.
The one certainty when discussing malware is the magnitude of the
problem it poses -- the damage inflicted globally by malware is
usually measured in billions . This overview briefly covers the
history of malware, the different strains, what makes today's
computers so hospitable and what the future holds.
Malware first entered the computer lexicon when the people
responsible for chronicling such topics -- journalists, analysts
and industry pundits -- realized they needed a broader term to
describe the profusion of malicious software running rampant across
the Internet. Before malware became a commonly used term, any
dangerous software was referred to as a virus or worm, which still
holds true today in the mainstream media. What distinguishes the
term malware from words like virus and worm is that malware refers
to the intention of the software's creator rather than a particular
feature of said software. While the term may be fairly new, the
software it describes is not.
Viruses and worms
Worms have probably been around the longest, though when they first
started surfacing they were hardly as malicious as today's malware.
A worm, as well as a virus for that matter, is a self-propagating
computer program.
The first well-known worm was known as the Morris Worm and it
used an early version of the Internet and a BSD Unix flaw to
propagate itself. In the recent past, hackers would often write
these pesky programs simply to prove that it could be done. That
was before every computer on earth was networked together via the
Internet, and viruses and worms often had to be physically
distributed to computers via floppy disk.
Viruses usually distinguish themselves from worms by requiring a
host, like a Word document. Though both viruses and worms can be
spread through email, viruses and unwanted email attachments have
become synonymous. The first widespread email-distributed virus was
1999's Melissa virus, which was a macro virus that exploited
Microsoft Word and Outlook to mail itself to an infected computer's
address book. Although viruses and worms can be damaging, their
implementation is often haphazard and less beneficial to their
creators than other forms of malware, which helps explain why this
oldest form of malware is dying out.
Spyware and adware
Just as widespread email use provided an enormous highway for virus
traffic, the growth of the Internet helped spawn spyware. Spyware
is an Internet browser-based malady that is largely fueled by the
prospect of monetary gain. In its least virulent form, spyware or
adware causes sluggish systems, slow Web browsing and annoying
pop-ups. The more dangerous spyware might track browsing habits or
sensitive information and transmit that information back to its
creator.
The term spyware is most commonly used to refer to the less
damaging adware. The surreptitious activity attributed to spyware
usually requires another piece of malware like a keylogger.
Bots, Trojans and keyloggers
The most recent trends in malware are related to the increasing
criminalization of online threats. One of these threats, bots, is
either on the rise or people are just starting to realize the
dangers of being infected by one. Bot makers and distributors
infect multiple systems to create massive botnets that can be used
to launch Distributed Denial of Service attacks or as spam
distributors -- which is, unfortunately, a lucrative endeavor.
Next on the list of growing Internet threats is the Trojan
horse. By definition a Trojan horse is just a means of secretly
installing a piece of malware on a system. That malware could be as
innocuous as adware or as dangerous as a keylogger or rootkit. The
name of the game for Trojans is subversion -- sneaking their way
onto a system and delivering an unexpected and potentially
devastating payload.
Flaws and vulnerabilities
So what makes malware so pervasive? You can often chalk up the
reasons for this deluge of depravity to software bugs, but even
perfectly operating software can be susceptible to attack. For
example, lax default configurations can either open up or
exacerbate vulnerabilities -- like when Windows 2000 Server had IIS
turned on by default, which contributed to the massive damage
inflicted by Code Red worm of 2000. Often Microsoft's zeal for
introducing new functionality opens security holes in software,
especially in Internet Explorer. But Microsoft is not solely to
blame for the rise of malware. A significant number of the most
vile threats require user interaction.
The future of malware
The bad news is that malware, once characterized by harmless
viruses and annoying adware, is increasingly used for criminal
activities. So much so that it is introducing new terms to the
computer world, like crimeware. Even completely novel applications
of computer code to the crimeware cause are surfacing. A new form
of malware known as ransomware attempts to hold a user's computer
files hostage.
Gone are the days when a hacker would announce his triumph with
an obvious mass-mailing virus. Nowadays, more malware writers are
creating subversive software. They wish to sneak onto systems and
secretly acquire sensitive user information or to even enslave
vulnerable machines. While wrong-doing is on their minds, financial
gain is usually the primary incentive.