

Trading stops at the end of day, for accounting purpose. Some traders can still access over-the-counter trades but they are not required to be reported (if I remember correctly) until sometime in the morning of the market they’re made in. You will see some price movement when London and the DAX open.
Watch futures for a good price estimate. ES for SPY and NQ for Nasdaq.
I’d argue security through obscurity was gone by 2000, for anything that can be pinged.