What is the TYPE of <denystrings> in <filteringRules>'s <requestFiltering>?

问题

<security>
<requestFiltering>
    <filteringRules>
      <filteringRule name="My filter" scanUrl="false" scanQueryString="false">
        <scanHeaders>
          <add requestHeader="User-Agent" />
        </scanHeaders>
        <denyStrings>
          -- I'm talking about the type of string in the following line --
          <add string="Mozilla" />
        </denyStrings>
      </filteringRule>
    </filteringRules>
  </requestFiltering>
</security>

I know that <add string="Mozilla" /> will look up the user agent for "Mozilla". In fact Mozilla will be %Mozilla% (if we talk like SQL).

Now I want to restrict access of the user agent "-" (not %-%).

Tell me are the strings' format, regular expression?

Are the strings Regular Expression? In PHP, I know Perl style regular expressions. Please tell me where can I find information about the type of the strings?

来源：https://stackoverflow.com/questions/20264389/what-is-the-type-of-denystrings-in-filteringruless-requestfiltering