Absolute PC Security and Privacy.pdf

So, thanks to VBA, an ambitious developer can inject a virus directly into the macro code in a
Word or Excel document. When you open the document, the macro code activates, and your
system gets infected.
This is a scary thought, as you probably exchange a lot of Word and Excel documents with
your work colleagues. Theoretically, any of these documents could contain a virus infection.
Fortunately, the danger of virus-infected documents appears to have subsided, to a large
degree. There are two reasons for this. First, newer versions of Microsoft Office applications
have included built-in protection against rogue macro code; in most instances, documents
aren’t allowed to run macros without your express permission. Second, this method of
infection is relatively difficult, and most virus writers have since migrated to other forms of
infection that hold out a greater promise of success.
Note Learn more about macro viruses in Chapter 4, “Macro Viruses.”
Through Commercial Software
You’d expect some amount of risk to be associated with blindly downloading unknown files
from the Internet, but you’d think that shrink-wrapped commercial software would be pretty
much guaranteed against virus infection. And you’d be right—to a point.
Mainstream software developers and distributors test their programs not only for bugs, but
also for viruses. That’s because a virus could possibly be inserted into the program code
during development, either intentionally by a malicious programmer or unintentionally by
other means. So the companies behind the programs go to great extremes to test for viruses
before their products ship, and to implicitly (if not explicitly) guarantee that their products are
virus-free.
So it’s fair to say that almost all commercial software programs are safe from viruses. But that
still leaves a slight margin for concern—because it’s possible (if not exactly probable) for a
virus to slip through all the detection and infect consumers’ machines.
In fact, there have been a handful of documented incidences of commercial software being
infected with computer viruses. While it’s not something to get overly worried about, it can
happen—and has happened. (For example, in Chapter 4 you’ll learn about the Concept virus,
which found its way onto two CD-ROMs distributed by Microsoft.)
The bottom line Using commercial software is one of the least likely ways to contract a
computer virus—but it’s not 100% safe.
Which Files Can Be Infected
With all this talk about avoiding files sent to you by other users, it’s important to note that not
all types of files can carry computer viruses.
What types of files can contain viruses