Merge pull request #209813 from RobdeJong/patch-163

Update how-to-connect-install-prerequisites.md

Author: prmerger-automator[bot]

articles/active-directory/hybrid/how-to-connect-install-prerequisites.md

@@ -83,6 +83,7 @@ We recommend that you harden your Azure AD Connect server to decrease the securi
 - Follow these [additional guidelines](/windows-server/identity/ad-ds/plan/security-best-practices/reducing-the-active-directory-attack-surface) to reduce the attack surface of your Active Directory environment.
 - Follow the [Monitor changes to federation configuration](how-to-connect-monitor-federation-changes.md) to setup alerts to monitor changes to the trust established between your Idp and Azure AD. 
 - Enable Multi Factor Authentication (MFA) for all users that have privileged access in Azure AD or in AD. One security issue with using AADConnect is that if an attacker can get control over the Azure AD Connect server they can manipulate users in Azure AD. To prevent a attacker from using these capabilities to take over Azure AD accounts, MFA offers protections so that even if an attacker manages to e.g. reset a user's password using Azure AD Connect they still cannot bypass the second factor.
+- Disable Soft Matching on your tenant. Soft Matching is a great feature to help transfering source of autority for existing cloud only objects to Azure AD Connect, but it comes with certain security risks. If you do not require Soft Matching, you should disable it: https://docs.microsoft.com/azure/active-directory/hybrid/how-to-connect-syncservice-features#blocksoftmatch
 
 ### SQL Server used by Azure AD Connect
 * Azure AD Connect requires a SQL Server database to store identity data. By default, a SQL Server 2019 Express LocalDB (a light version of SQL Server Express) is installed. SQL Server Express has a 10-GB size limit that enables you to manage approximately 100,000 objects. If you need to manage a higher volume of directory objects, point the installation wizard to a different installation of SQL Server. The type of SQL Server installation can impact the [performance of Azure AD Connect](./plan-connect-performance-factors.md#sql-database-factors).