Twenty-five years ago, the notion was you could create a general problem-solver software that could solve problems in many different domains. That just turned out to be totally wrong. ↗
Limit use of shareware and public domain software to systems without fixed disks. If you do use them on fixed disks, allocate separate subdirectories... Public domain or shareware software should never be placed in the root directory. ↗
I think malware is a significant threat because the mitigation, like antivirus software, hasn't evolved to a point to really mitigate the risk to a reasonable degree. ↗