(Adds details from report, background on proxy fight) By Svea Herbst-Bayliss BOSTON, Aug 23 (Reuters) - Proxy advisory firm Institutional Shareholder Services on Monday backed cloud storage vendor Box Inc in its fight with activist investor Starboard Value by recommending that shareholders vote for the company's directors instead of the hedge fund's nominees. In its report, ISS said shareholders should vote for Box directors Peter Leav and Aaron Levie, arguing that the current board has made sensible changes and should get more time to effect a turnaround.