Recently I responded to a suggestion that I "upgrade Flash" on my macOS system only do end up with several applications running, and intruding into my browser and desktop that I did not (mean to) install:

  • Mac Ads Cleaner
  • Mac App Cleaner
  • Porn Cleaner

I followed instructions I found online for removing these apps and believe they are gone (Bitdefender's virus and malware virus scan shows no remaining malicious software).

However, I wonder what they did while they were on my machine. What I could see is that they were very intrusive: launching themselves, setting themselves up to re-launch on start, resetting my browser's homepage to a spoof "safe" search engine — even popping up a window when they were installed by moving to the Trash. But I would like to know what else they did while installed *that I couldn't see.

What do these apps do? Have they done any lasting damage? Or are they only a nuisance while installed?

Note that this is not a duplicate of this question. Here the question is what these specific (and common and well known) apps did when installed. (For example, did they capture passwords, erase files, etc.?)