Does anybody know the following graphic (see the two attached screenshots) which is built up line by line from bottom to top of the screen across the whole width some time before Login?

I do not remember exactly what it did when the entire screen was filled up with the pattern after about two seconds. I think I have observed all of the following:
1) frozen screen, restart by C,A,D
2) frozen screen, restart by reset only
3) automatic restart.

Is it a problem with the graphics card? Should I worry because it is created by some malware or is it harmless?

DSCF0707.JPG
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DSCF0708.JPG
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does this happen all the time? if yes then your graphics card might be failing.

Cudni

No, it happens sporadically in the order of magnitude of some weeks or months depending on the state of the system (maintenance work or follow-up of known system weaknesses or errors). I cannot predict when it will happen but the probability for such a failure to happen would rise when I have strained the system by doing much work on graphics or music or internet without timely maintenance work.