[GRLUG] $50K Prize if You Find Way to Block Robocalls

[Tim Schmidt]

I think the answer is doubly that they have more data, and that they
keep it secret.

Sharing the data means sharing it with the spammers, and in my short
time as an email admin, subscribing to the popular spam lists only
blocked about half our incoming spam.  Even with greylisting, lots of
filter tweaking for company-specific domain terms, scads of training,
and measures I've since forgotten, we still regularly received spam.
Those guys are really good at what they do.

I'll freely admit that having an expectation of 0 false positives or
negatives is unattainable.  However, that _is_ the goal.  And even
google misclassifies a message or two a month on me.