The Scot started the tournament in 10th place on the Race to London standings, but is now up to eighth - the final qualifying berth - after victory over one of his rivals for a spot at the season-ending event.
Spain's Ferrer was the top seed in the Austrian capital and won the first set of today's final by breaking Murray in the 12th game to snatch it 7-5.
Ferrer then held at the start of the second, but Murray won six of the next seven games to romp to a 6-2 success and force a decider.
It was a topsy-turvy third set, with Murray eventually prevailing 7-5 after seven breaks of serve.
The two-time Grand Slam champion has two more tournaments, in Valencia and Paris, to put more points on the board and secure his place at next month's tournament at the O2 Arena.