A towering figure
I haven't much to add to the excellent obit (thanks Connor), except to +1 that Security Engineering is an absolutely essential book for the shelves of anyone with even a non-professional interest in infosec; and to note that one reasonable proxy for measuring his significance might be the number of times he was involved in stories reported here on the Reg.
(Sadly and inappropriately, I can't get DuckDuckGo to do the equivalent of the chocolate factory's "site:.." flag.)
https://www.google.com/search?q=%22Ross+Anderson%22+site%3Atheregister.co.uk