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.
  • wpgwpg
    I have two antivirus programs that are working with no problems. Norton and Defender. I don't know what you're using, but I can attest to these two not having problems.
  • farnell121
    This is the best time to switch to Linux. I am normally OS agnostic and find pros/cons in each platform, but after working in even the Medical Software industry I am horrified at how toxic these updates are becoming.

    I now use Manjaro and Kubuntu on all of my devices, I have Office 2016 and proprietary software (mostly) working under Linux, with the web versions working flawlessly. Now that I'm able to launch 90%+ of my Windows-only Steam titlesusing Proton, and the fact it comes working out of the box in Manjaro should have Microsoft worried.

    The revolution is coming!
  • Druidsmark
    Actually since the latest update Kapersky Internet Security 2019 works fine, but now when I reboot my pc Windows Defender Security Center does not load correctly so have to reboot the pc a few times to get it to load correctly at windows start up, using Windows 10 pro. So not only has Microsoft created bugs related to other antivirus software but they have created bugs in there own security software.
  • NahNood
    wpgwpg said:
    I have two antivirus programs that are working with no problems. Norton and Defender. I don't know what you're using, but I can attest to these two not having problems.
    Wow, Norton actually did something right?! Cool. :)
  • JamesSneed
    NahNood said:
    Wow, Norton actually did something right?! Cool. :)

    Norton has done well for me over the last few years. Going back 5+ years they used to be a mess.
  • TechyInAZ
    I'm using Webroot and not even a hint of a slowdown on my system.
  • CountMike
    Only one with problems that I know of is Avira on Cumulative Update KB4493509 Windows 10 v1809 Build 17763.437
    Several patches from Avira maker later and is not resolved yet.
  • CerianK
    Everyone is assuming/reporting 3rd party anti-virus is causing the issue... which may be the case.
    However, that is kind of like saying that people with PCs are affected... somewhat vacuous.

    Here, I have an Acer laptop with no 3rd party AV (removed completely over a year ago)... crawls after login since Windows 10 updated on the 9th.
    Some programs take 1 hour to launch. Task Manager opens in 2 or 3 minutes if you wait 10 minutes for the desktop to finish loading.
    Works fine if you can live life on that time-scale without anger.

    Who knows, might be something else going on, as USB drive with some programs installed loads those programs quickly.
    I was going to install an SSD on it anyway and have one ordered, since SMART has been monitoring a few hundred sectors for a month.
    I just wanted to clone the drive to it first before taking further action. Restore point from 9th didn't install for some reason.
    Hopefully that is all it needs, since I would hate setting up the OS after a complete system restore.

    Edit: It turns out that the Toshiba HDD has reached its end. Connected drive to another PC and Macrium Reflect struggles to image it. It is sad that Windows 10 decided to update (pushing the drive over the edge) rather than gather SMART info to see if the update made sense in the current health context of the drive (and suggest to image first). The drive belongs to my son, but ultimately I will be the one to install Windows if the image does not complete or work once restored to the new SSD.
  • AllanGH
    If you stacked up reports of microsoft updates / service packs breaking something that wasn't obviously broken before....well, you might want to do that in a cathedral....something with a 30 metre vaulted ceiling outta do it.
  • Victor Bettenhausen
    Lucian Armasu said:
    A recent change to a core component in Windows 10 seems to have broken multiple antivirus programs.

    Latest Windows Update Breaks Many Antivirus Programs : Read more
    I'm curious as to why I haven't experienced any problems after installing any of the Windows 10 updates. My system is used primarily for photo processing using Lightroom, or Capture One Pro. I use Avast antivirus without any issues.
    My current system configuration:
    Motherboard - Asus X370-A
    Memory - 32gb (16x2) Mushkin Redline 2666 (runs good at 3000)
    CPU - AMD Ryzen 7 1800x
    Graphics - AMD Radeon Pro WX5100
    Primary SSD - Samsung 850 Pro 256