They look for accounts that make consistently "lucky" large trades during blackout periods before earnings but at or just after the close of the quarter. Then t

They look for accounts that make consistently "lucky" large trades during blackout periods before earnings but at or just after the close of the quarter. Then they run the SSN/address/bank accounts/phone # associated with the trading account and compare to lists of insiders supplied by companies of who has access to their financial info. I think they also have separate flags on insider's tax returns to look for any unusual capital gains from market transactions. It's not a trivial problem to make trades in an account completely unrelated to you and then get the illegit proceeds back into your control without tripping some flags. Also, most of the volume in these stocks are huge algorithmic trades from institutional investors and funds. They also tend to move in herds based on when analysts release new reports or change ratings on the stock. Thus, those are pretty easy to filter out of a search. Unusual trades from individual brokerage accounts are going to stand-out. Especially if those accounts aren't making similar trades in other stocks. When they get suspicious matches they run them down to see if there's anything there. I used to be an insider at a big tech company and there's quite a bit of scrutiny. You'd have to be really stupid to do that shit. Especially repeatedly with large amounts.