The online analytics firm KISSmetrics quietly overhauled its web tracking methods over the weekend, and is now permitting users to block its surveillance, in a hurried response to a report slamming the company for using sneaky techniques to track web users who visit some of the biggest sites on the net.

The 17-person Bay Area startup made the changes after two of its highest profile customers — Hulu and Spotify — suspended their use of the service on Friday in light of the research and the Wired.com story that was first to report it. Separately, Hulu and KISSmetrics were also sued in federal...