Complaints were filed within days of a paper published by internet privacy researcher Ashkan Soltani and others which took issue with the company’s use of ETag technology to track website visitor behaviour.

ETags are stored in a computer user’s browser cache so they are unaffected when cookies are deleted. But the information these ETags contain allow for deleted cookies to be recreated so web tracking can continue.

The complaints centre on the fact that Kissmetrics’ technology would allow a website user to be tracked when they had a reasonable expectation not to be – through changing browser privacy controls or deleting cookies.

But on a wider pointt, one of the suits picks up on speculation made in the Soltani paper that Kissmetrics can track individuals across websites through the use of a shared identifier. But Shah says: “This has never occurred.”

Writing in a blog post, he said that Soltani’s “misinformation appears to result from the fact that we use the same URL for all customers to reduce server and bandwidth resources and increase end-user performance.

“An incidental consequence of this is that the same anonymous identifier was returned across multiple websites. However, internally these identifiers are instantly translated into unique identifiers for each customer, and Kissmetrics has gone to extensive lengths to avoid linking any information from different customers, including segregating each customer’s data in a completely separate database.”

Since the Soltani paper was published, Kissmetrics has overhauled its tracking system to do away with ETags and other forms of persistent cookies and objects and says it will now only use first-party cookies. It has also added support for do-not-track headers and a consumer-level opt-out.

Shah says the company will fight the lawsuits “head on”.