Any way to limit the "size" of a synchonization job?

[merwinsson]

I've been using FreeFileSync for years to backup my fileserver to another backup fileserver.
I use the Mirror (with versioning) Sync type, and it's been working nicely.
An automated script runs a sync at 3AM every day.
However, there was once a time when a ransomware virus invaded the main fileserver and changed everything.
Fortunately, I was able to stop the daily synchronization before it changed everything on the backup fileserver.
Normally, only a few files change from day to day, so either a large amount of file changes or a large amount of byte changes is a very serious red flag that signals that I don't want to proceed with syncing.
Is there anyway I could configure FreeFileSync to abort its sync if, after the compare phase, the number of changed files exceeds some numeric threshold, or, similarly, the number of bytes that will be written exceeds another set numeric threshold?
This would help avoid hours and hours of moving versioned files back to their original names and locations.

[xCSxXenon]

There is a warning in FFS if folders are significantly different, most users have hidden this. You can unhide it in settings. Other than that, FFS isn't the correct way to do this. It is not a malware/ransomware detector, it is just a file sync tool. There are utilities out there made to monitor exactly what you want though, such as ones that save file hashes and compare them to detect corruption. This is also why off-site and air-gapped backups are part of a complete backup plan

[merwinsson]

So I believe I found the option in the GlobalSettings.xml that governs the warning you speak about.
<OptionalDialogs><WarnSignificantDifference Show="true"/>
This looks promising.
I guess I need to look up whether this will STOP the sync, because that's what I want.
And also how does this work when the sync is running in the background as a batch job.
Investigating.
Thanks for the lead.