<Safe Control/>
<!– web.config in root directory of hosting virtual server -->
<configuration>
  <SharePoint>
    <SafeControls>
      <SafeControl Assembly="AcmeWebParts"
                   Namespace="AcmeWebParts"
                   TypeName="*"
                   Safe="True" />
   </SafeControls>
  </SharePoint>
</configuration>
Instructor Notes
WSS V3 will only load and run Web Parts that have been marked as safe controls in the web.config file of the hosting WSS Web application. The motivation for why WSS requires safe control entries has to do with defending against attacks. For instance, think about a malicious individual who manages to get a read\write connection to the content database.

What if this person uploaded or modified a .aspx file with an ASP.NET control or added a Web Part into a Web part zone in order to conduct an attack. This attack can be defeat by the fact that an administrator of the local Web server gets to specify the exact set of ASP.NET controls and Web Parts that can be loaded on a Web application by Web application basis.