A Windows update may have broken your Mac’s access to shared servers. Here’s how to fix it

Image result for A Windows update may have broken your Mac’s access to shared servers. Here’s how to fix itFixing security holes sometimes causes problems in perfectly normal activities. That’s the case if you’re a macOS user who relied on a specific kind of login method for Windows and Windows Server file sharing before June 2019. Microsoft released a fix for NTLM, a technology for managed authentication and security that dates back over a decade in its first version.

Two critical bugs in NTLM required updates for a seemingly every version of Windows and Windows Server released for several years that incorporate NTLM. These necessary updates broke Mac-based login sessions using standard Windows file-sharing protocols long supported in macOS.

If you’re in that boat and receive an error that there was a problem connecting to the server, you can follow Apple, Microsoft, and third-party advice to re-connect.

  • In Yosemite (macOS 10.10) and later, connecting in the Finder by select Go > Connect to Server and entering smb:// plus the IP address or full name of the server. This will create an up-to-date SMB connection.
  • If you have Kerberos authentication available, switch to that method for logging in, but the server has to have a DNS name and that name must be used instead of an IP address on the local network.

Apple also suggests that a Windows Server system administrator can enable “server message block (SMB) signing,” which reduces performance, but allows backwards-compatible connections from older Macs.

Ask Mac 911

We’ve compiled a list of the questions we get asked most frequently along with answers and links to columns: read our super FAQ to see if your question is covered. If not, we’re always looking for new problems to solve! Email yours to [email protected] including screen captures as appropriate, and whether you want your full name used. Every question won’t be answered, we don’t reply to email, and we cannot provide direct troubleshooting advice.