Clarify unprotected simple bind settings

doc/guide/admin/security.sdf

@@ -146,6 +146,11 @@ is protected by other means (e.g., TLS, {{TERM:IPSEC}}).  Where the
 administrator relies on TLS to protect the password, it is recommended
 that unprotected authentication be disabled.  This is done by setting
 "{{EX:disallow bind_simple_unprotected}}" in {{slapd.conf}}(5).
+The level of confidential protection to require can be adjusted
+using the {{overall}} security strength factor using the {EX:security}}
+directive.  If this factor is not set (or set to integrity only),
+any confidentiality protection is sufficient.
+
 The user/password authenticated bind mechanism can be completely
 disabled by setting "{{EX:disallow bind_simple}}".