Firefox engineers discover a Windows Defender bug that causes high CPU usage

Post by psychphysic » Wed, Apr 05, 2023, 7:51 PM UTC

IronWolve wrote: post #27

mconley wrote: post #4

TL;DR: Windows Defender had a bug that made certain system calls expensive on CPU cycles when Defender's Real-time Protection feature is enabled. After discovery, Mozilla reported this issue to Microsoft. Microsoft is releasing a patch that should result in lower CPU usage when using Firefox on sites like YouTube (a ~75% CPU usage reduction was noted when browsing YouTube in Firefox with the fixed version of Defender…

It's not just mozilla, been working defender issues for the last few years on thousands of windows vm's. Mostly due to the enabling the more intensive heuristic real time engine and they have different code bases depending on versions installed on different windows builds, and patching does seem to trigger it. For months we had issues where we couldnt log into some vm's due to high cpu for defender, and had to bounce…

Post by Cthulhu_ » Wed, Apr 05, 2023, 7:54 PM UTC

boringuser2 wrote: post #21

marcodiego wrote: post #13

> a ~75% CPU usage reduction was noted when browsing YouTube in Firefox I wonder how many of the people who say "Firefox is significantly slower than chrome" are using windows... On my computer, Firefox IS slower than chrome but (with ad blockers enabled) by an insignificant amount. By still being "the last remaining mostly independent, maintained and reasonably popular browser" I'd prefer it to use over chrome even…

Firefox is significantly slower than chrome. This usually doesn't matter, but you can immediately see it in any page that A) has a massive DOM or B) uses complex regular expressions that eat up the engine

Post by Diggsey » Wed, Apr 05, 2023, 7:55 PM UTC

mconley wrote: post #4

TL;DR: Windows Defender had a bug that made certain system calls expensive on CPU cycles when Defender's Real-time Protection feature is enabled. After discovery, Mozilla reported this issue to Microsoft. Microsoft is releasing a patch that should result in lower CPU usage when using Firefox on sites like YouTube (a ~75% CPU usage reduction was noted when browsing YouTube in Firefox with the fixed version of Defender…

Post by Cthulhu_ » Wed, Apr 05, 2023, 7:56 PM UTC

ivanmontillam wrote: post #25

I've experienced a bug related to the on-disk real-time scanning of Windows Defender, but instead with 100% disk bandwidth usage for unreasonable amounts of time. I purchased a license of a proper antivirus software to avoid that bug and the performance issues gone away. When you install another AV software, Windows Defender steps down and leaves scanning to the 3rd-party security solution. I selected one of the most…

Post by jacobsenscott » Wed, Apr 05, 2023, 7:59 PM UTC

moonchrome wrote: post #28

This just reminds me of constant "things worked so fast on my Windows 95 machine back in the day with 16MB RAM". Meanwhile any piece of software could crash your PC and it did so regularly (I still keep spamming save in software because of those days) and internet was a pandoras box. I wonder how much overhead in modern OS/PC user experience comes from security/stability abstractions and tools.