I am having this issue as well. I am using Windows 10. I uninstalled my previous version of Avast, downloaded malaware bytes, ran a scan, then downloaded the latest version of Avast and installed it. Then scanned again. All scans found nothing, comp is completely clean. Avast was good for about a week, now its happening again, keeps shutting off randomly. Could someone look into this? because it seems like an Avast issue…
Same here, on the latest Windows 11 25H2. From 25.12 or, maybe, 25.11, but not so often, Avast keeps turning off the Behavior and Ransomware shields after a few minutes. The problem did not exist before. Initially I thought it was about my encrypted DNS settings, but I removed them, uninstalled and cleaned the remnants of Avast or AVG(they have the same problem) and reinstalled with the default ISP DNS. The problem persists. I installed the 25.10 version, it worked ok, but after an hour or two or a restart, although I set it specifically to update only manually, it updated itself to 25.12 and the problem appeared again. P.S. The system is clean, checked wth Avast, AVG, Bitdefender and Eset Antivirus, in bootable disk mode.
I tried for three days the 25.10 versions of Avast and AVG(I had the install files), with all the executables blocked in firewall to update(if you don’t block it, it will update to 25.12 anyway, no matter what the setting for program updates are; and, if you install it with the internet on, after install it will tell you that it needs updating and it will have a crippled interface, turn of the Internet before installing it), the signatures being the initial ones, from October 13, 2025. That version works flawlessly on my system, I can turn off the Antivirus for whatever time I want and then restart it or whatever and it just works. It doesn’t matter if the DNS is encrypted or not, it works. The 25.12 disables its Behavior and Ransomware shields after a few minutes of working. So yeah, something in the 25.11 or 25.12 version is causing something to behave this way. And the problem is in both Avast Free Antivirus and AVG Free Antivirus 25.12 version and not in the 25.10 one, they behave the same, so they must share something that makes them do that.
After the 26.1 update, the problem persists, nothing’s changed. Only the behavior and ransomware shields disable themselves after you turn the antivirus off and on again from the slider on the right click tray icon.