Possibility of untraceable widescale nuclear attack?

Is it plausible that a fleet of missiles could rain down from deeper space on a target untraced?

One problem would be the number of players with the tech to do it. Another would be the be the initial part of the trajectory possibly years earlier being detected. But what wvould be needed would just enough anonymity to prevent an ICBM retaliation.

The alternative is stuff on quadcons. Its been said the bigger powers have aready each other’s territories with hidden nuclear devices.