User Guide

User’s Guide 283
Using Specialized Scanning Tools
Figure 8-3. Advanced Scan Settings dialog box
Heuristic scanning technology enables the E-Mail Scan extension to
recognize new virusesbased on their resemblance to similarviruses that
the module already knows. To do this, the extension looks for certain
“virus-like” characteristics in the files you’ve asked it to scan. The
presence of a sufficient number of these characteristics in a file leads the
extension to identify the file as potentially infected with a new or
previously unidentified virus.
Because the extension looks simultaneously for file characteristics that
rule out the possibility of virus infection, it will rarely give you a false
indication of a virus infection. Therefore, unless you know that the file
does not contain a virus, you should treat “potential” infectionswiththe
same caution you would confirmed infections.
The E-Mail Scan extension starts out without any heuristic scan options
active. To activate heuristic scanning, follow these substeps:
a. Select the Enable heuristics scanning checkbox. The remaining
options in the dialog box activate.
b. Select the types of heuristics scanning you want the E-Mail Scan
extension to use. Your choices are:
– Enable macro heuristics scanning.Choosethisoptionto
have the extension identify all Microsoft Word, Microsoft
Excel, and other Microsoft Office files that contain embedded
macros, then compare the macro code to its virus definitions
database. The extension will identify exact matches with the
virus name; code signatures that resemble existing viruses
cause it to tell you it has found a potential macro virus.
– Enable program file heuristics scanning. Choosethisoption
to have the E-Mail Scan extension locate new viruses in
program files by examining file characteristics and comparing
them against a list of known virus characteristics. The
extension will identify files with a sufficient number of these
characteristics as potential viruses.