Page 62 - Microsoft Office Excel 2003 Programming Inside Out

Microsoft Office Excel 2003 Programming Inside Out

Figure 3-10. Breakpoints let you run your code to a specific point before you step through it
line by line.

Implementing Macro Security and Digital Signatures

Chapter 3
Viruses and other forms of harmful software (sometimes called malware) are a fact of life you
have to deal with when you work with a powerful and flexible programming language such as
VBA. You should already have a virus checking program or two installed on each of your
computers to act as the first line of defense against macro viruses (viruses written using a
macro programming language), but new viruses pop up all the time and it’s possible that
your detection programs won’t recognize newer threats. After your second line of defense,
which is you casting a critical eye on every file you receive, expected or not, you have the Excel
macro security settings.

Tip Avoid Running Auto Macros
If you want Excel to start without running an Auto_Open macro, hold down the Shift key
when you start the program.

The Excel macro security settings determine how permissive Excel should be about allowing
macros to be run on your computer. There are three macro security settings: High, Medium,
and Low, which you can control by clicking Tools, Options, Security, Macro Security to display
the Security dialog box.

You should cross the Low option off your list of acceptable macro security settings; even if
you have an all-but-foolproof virus scanner, allowing even one virus to get through is one too
many. No software can know what files you are or aren’t expecting, so you need to make sure
there’s an active human in the security loop. That human is you.

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Part 2: Visual Basic for Applications