[German]A German blog reader contacted me a few days ago with a strange observation. The reader uses a backup solution that is launched cyclically via the Windows task scheduler. Since December 2024, however, the reader has noticed that the tasks of the task scheduler no longer run cleanly, but are deactivated. It affects a Windows computer in his environment, and it was unclear what is responsible for the deactivation of the backup task. After publishing the German blog post, the reader found out, that CCleaner was the culprit.
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Blog reader Norbert H. has been using Lindenberg-Backup for years as a solution for backing up his systems. According to him, most of the computers are running Windows 10, one system has been converted to Windows 11.
Backup with Lindenberg-Backup and task scheduling
The Windows systems are to be backed up on Tuesdays and Thursdays. This is controlled via an entry in the task scheduler, which then calls up the backup software.
Task is deactivated in task scheduler
So far, this approach has worked very well. But since December 5, 2024, there has been a problem on one of the "external" computers that the backup does not start on the scheduled dates. The reader then checked and found out that the relevant entry for the scheduled task in the scheduler has been set to disabled.
If the reader activates this task and starts the backup manually, it runs through once. On the other hand, he found that this process was canceled after approx. 30 minutes in three tests. In these cases, he was able to determine that the task (backup task) had then been set to deactivated again in the task scheduler.
Norbert asked if I knew of any security software that disables something like tasks in the task scheduler (this Microsoft Answers forum post from 2023 mentions such a problem as the cause). He is running Bitdefender on the computer in question. Ad hoc, I am also not aware of any problems with task scheduling.The reader then asked for a way to extend logging in the Task Manager (switching on logging is mentioned here, for example, and how to find out which account deactivates the task is also touched on here, but does not help in all cases). The user's aim is to see why the task is deactivated in the task scheduler and which process is causing this. According to the reader, the Windows Event Viewer only shows that the task is deactivated by the Task Scheduler, but does not specify why or what triggers this change.
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And the culprit is CCleaner
It is now clear that my "personal favorite", CCleaner, was the culprit (I had assumed that this program was no longer really used due to many problems). The reader reported this to me in a 2nd mail The "Performance Optimizer" in CCleaner is doing this nonsense. I'll leave it here as a warning.
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