Security Level
Select the macro security level from one of four options. The options differ according to the security level. Macros that are allowed to run on a higher security level are also allowed to run in all lower levels.
Very high
Only macros from trusted file locations are allowed to run. All other macros, regardless of whether they are signed or not, are disabled.
Trusted file locations can be set on the Trusted Sources tab page. Any macro from a trusted file location is allowed to run.
High
Only signed macros from trusted sources are allowed to run. Unsigned macros are disabled.
Trusted sources can be set on the Trusted Sources tab page. Only signed macros from a trusted source are allowed to run. In addition, any macro from a trusted file location is allowed to run.
Medium
Confirmation required before executing macros from unknown sources.
Trusted sources can be set on the Trusted Sources tab page. Signed macros from a trusted source are allowed to run. In addition, any macro from a trusted file location is allowed to run. All other macros require your confirmation.
Low (not recommended)
All macros will be executed without confirmation. Use this setting only if you are certain that all documents that will be opened are safe.
A macro can be set to auto-start, and it can perform potentially damaging actions, as for example delete or rename files. This setting is not recommended when you open documents from other authors.