Can't speak specifically for that one, but whenever I'm concerned about anything maccy I check out either/both of these sites https://discussions.apple.com/community/mac_os http://www.macrumors.com
and generally can find reassurance from specialists or have posted a question myself and had fairly swift and satisfactory answers...
dw...if it is Flashback then that was fixed way way back in 2012 by Apple issuing a security patch. This suggests that your son is not bothering to keep his software updated regularly.