The Windows update, released on April 9, causes problems with security programs from several manufacturers. The list of programs is getting longer, but the cause is still unknown. On the same day, a test version of the Windows 10 May Update was released, but this is not about it.
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At the time of writing the article on the list of problematic programs were business products of Avast, Avira, Sophos, ArcaBit, and the latest reports concern McAfee anti-viruses.
Computers with these programs installed run smoothly until the first restart. After restart, logging in is not possible. The system writes, reads, counts, and finally the load reaches a level where it cannot be used. It is difficult to say whether it stops or if Windows is just running very, very slowly.
Some users report that they finally managed to log in, but they waited several hours.
The problem does not occur on Windows 10
Login problems appear in older versions of Windows. They are on Windows 7, 8.1, Server 2008 R2, Server 2012 and Server2012 R2. You can use login in safe mode, which works without problems.
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There are several ways to deal with the problem. It is recommended to start the computer in safe mode and disable the antivirus program. After that, Windows should start normally.
Sophos reports that adding a program folder to the search engine exceptions list helps him – this is weird, but it works. Avast has yet another solution to the problem. The company recommends leaving the login screen for about 15 minutes and restarting the computer. Avast should then update in the background. The corresponding amendment has already been issued by the manufacturer for Avast and AVG products.
Currently, Microsoft is blocking the update for users of Sophos, Avira and ArcaBit products. The issue of McAffee programs is under investigation.
A small change, a big problem
McAfee suspects the cause of the failure. In the April patch, Microsoft introduced changes to the client-server subsystem (CSRSS). This is a key part of Windows that coordinates the work of Win32 applications. This change caused many anti-virus programs (mainly for companies) to be blocked. The program tried to access some resource, but the subsystem did not allow it, because … the same program had exclusive rights to that resource.
The burden of making patches accepted by antivirus producers. Since Microsoft does not restore the previous behavior of CSRSS, it means that the change may have discovered some old bugs in security programs. Let it be so. Windows updates have a reputation of problematic and unreliable.