Items related to messaging services with a focus on Exchange Online (EXO) and Exchange server (on-premises)
A common issue when deploying Exchange Online Protection (EOP) and Microsoft Defender for Office 365 (MDO) with on-premises Exchange is making Exchange aware of the EOP spam filtering. This is because EOP uses slightly different logic to stamp the spam results etc. into the message. Exchange Server needs to be aware of this so that it can take action upon those settings.
The November 8, 2022 and later Windows updates address a security bypass and elevation of privilege vulnerability with Authentication Negotiation by using weak RC4-HMAC negotiation.
This update will set AES as the default encryption type for session keys on accounts that are not marked with a default encryption type already.
To help secure your environment, install the Windows update that is dated … Read the rest “Kerberos Issues November 2022”
Extended Protection (EP) was added to Windows back in 2009 as a new security feature. This feature enhances the protection and handling of credentials when authenticating network connections using Integrated Windows Authentication (IWA).
The update itself does not directly provide protection against specific attacks such as credential forwarding, but allows applications to opt-in to Extended Protect… Read the rest “Updated Guidance On Exchange Server Extended Protection”
There are a multitude of online tools that help diagnose issues with various mail services, but understanding what these tools actually check is valuable. One example is around manually checking published DomainKeys Identified Mail (DKIM) records. DKIM is described in RFC 4871. As an interesting piece of history DKIM went through a previous iteration "Domain-Based Email Authentication Using Pub… Read the rest “How to Use NsLookup To Check DKIM Record”
Extended Protection uses service binding and channel binding to help prevent an authentication relay attack. In an authentication relay attack, a client that can perform NTLM authentication (for example, Windows Explorer, Microsoft Outlook, a .NET SqlClient application, etc.), connects to an attacker (for example, a malicious CIFS file server). The attacker uses the client's credentials to masquer… Read the rest “Exchange Server Extended Protection”
The May 2022 security update for Exchange Server 2013, 2016 and 2019 resolved CVE-2022-21978. A common issue is that admins are only doing part of the work to address this CVE. Yes they are installing the update, but are not reading the rest of the documentation which states that an additional command must be run.
The FAQ states:
Do I need to take further steps to be protected from this vulnerabil… Read the rest “Remediate Exchange Security CVE-2022-21978”
Note that there have been changes to Safe Links policy for Microsoft Defender for Office 365 (MDO).
Previously you could add URLs to the Safe Links policy to control how MDO would process the URLs. As part of this change the URL blocking is moving to the Tenant Allow Block List (TABL).
Below is a screenshot showing that a previously entered URL needs to be migrated to TABL.
&nb… Read the rest “Migrate Safe Links Block Settings to TABL”
In the field, I’m seeing multiple customers that are struggling to implement the DownloadDomain feature. It does require a little prep work and it is not as simple as just running a single command in Exchange to flip the setting on.
In order to mitigate and issue with OWA, it is necessary to create an additional CAS namespace that will be used for downloading attachments from OWA. This will requir… Read the rest “Implementing Exchange DownloadDomain Security”
When designing an upgrade strategy from an older version of Exchange to a newer one, a question that needs to be addressed is do we need to introduce a version of Exchange that may not currently be present? This may be when upgrading from Exchange 2013 to Exchange 2019. If that organisation currently does not have any Exchange 2016 servers, you need to evaluate if there may be a future requireme… Read the rest “Exchange 2019 Point of No Return”
When delivering Office 365 Security Optimisation Assessments (SOA) to customers, one of the control items is the version of Azure AD Connect deployed along with some related configuration elements. In many cases, Azure AD Connect is not updated to a build that resolves both security and feature issues. Why is Azure AD Connect not current? Good question.
There are two main scenarios that I see rig… Read the rest “Upgrade to Azure AD Connect 2.0”