"They may all do similar scans... but then exploiting any found vulnerabilities to take screenshots is most definitely of questionable legality"
They are not exploiting a vulnerability. These numptys have their systems open to everyone on the planet with no password.
Anyway, djack beat me to it -- back in "the good old days" (early 1990s), the local hacking group wardialed our area (i.e. all numbers that were not long distance). The number of unpassworded systems was fairly ridiculous. PCAnywhere alone? A hair cutter was wide open; a few unidentifiable desktops were wide open; a climate control/elevator control for a store was wide open. The *police department*? Wide open. Boy that could have been fun 8-) , lucky for them none of the local group were truly blackhats. There were 6 or 8 other systems that were wide open but text-based (besides the couple BBSes and so on that were common knowledge.)