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Latest Windows Update Breaks Many Antivirus Programs

(Image credit: Tom's Hardware)

The latest Windows update released on April 9 seems to have broken multiple antivirus programs, including Avast, Avira, ArcaBit, McAfee, and Sophos. Computers that are affected by the latest bugs run fine until users attempt to log in. At that point, the operating systems start freezing or just run extremely slowly. Windows 10, as well as Windows 7, 8.1, Server 2008 R2, Server 2012, and Server 2012 R2,  are all affected.

April 9 Windows Patches Cause Systems to Slow Down

After delivering the latest major update to Windows machines, Microsoft has begun adding antivirus clients to its list of programs that are impacted by it. Many users have reported that when running Avast, Avira, ArcaBit, McAfee, and Sophos, their operating systems become highly unresponsive when at the Windows login screen.

Some of the users affected by the latest bugs were able to login into their computers, but it took them ten or more hours. Avast recommended its users to leave systems at the login screen for 15 minutes before attempting to login. Afterward, the Avast update will run in the background. ArcaBit and Avira have published updates that promise to solve the problem for their users.

Users can also boot into safe mode to uninstall their antivirus programs if they want to solve the issue immediately, as the safe mode is not affected by it.

Antivirus Vendors Blame Microsoft For Underlying Change

Avast and McAfee have pointed the finger at Microsoft as the party responsible for all of the recent antivirus issues. Microsoft recently made a change to the client/server runtime subsystem (CSRSS), which is a component of Windows that coordinates and manages Win32 applications. This change has led to the freezing of antivirus clients. The antivirus clients attempt to access a resource, but they are blocked from doing so.

Now that antivirus vendors are more aware of this change (it’s unclear why they weren’t when the change happened in the Insider Preview phase of development), future updates should fix most of the clients.

Lucian Armasu
Lucian Armasu is a Contributing Writer for Tom's Hardware US. He covers software news and the issues surrounding privacy and security.