Is malicious contact by the defense considered a dead ball or delayed dead ball? What is the penalty for the defense and do advancing runners during the time of the malicious contact get the next base?

Malicious contact initiated by the defense would be either Obstruction if a play is in progress and the fielder does not have the ball, or unsportsmanlike conduct. Obstruction is a delayed dead ball situation so runners may continue to advance until playing action has stopped. Likewise, an unsportsmanlike act is not penalized while a play is in progress.

Either way, the guilty fielder is through for the day.