When you send a direct message on Twitter, you might imagine it zipping straight from your account to its intended recipient, arriving exactly how you wrote it, untouched and unchanged. But a new lawsuit in California claims Twitter is effectively snooping on users’ direct messages, and changing them to benefit its own advertising goals.

A lawsuit seeking class-action status [PDF] filed on Monday in a San Francisco federal court claims Twitter “surreptitiously eavesdrops on its users’ private direct message communications. As soon as a user sends a direct message, Twitter intercepts, reads and, at times, even alters the message.”

As for how those messages are allegedly altered, the lawsuit claims Twitter’s algorithm searches direct messages for links, then changes them using its own link shortening tool. This, despite the fact that link shortening tools aren’t as necessary now that direct messages have been freed from the 140-character limit.

“Twitter’s algorithms will read through the Direct Message, identify the hyperlink, and replace it with its own custom link, thereby sending the person clicking on the link to Twitter’s analytics servers before passing them on to the original linked-to website,” claims the suit, which was originally reported by the Hollywood Reporter.

The suit uses the example of a story a user might send from the New York Times to another follower via direct message, using the full URL. Twitter will modify it to something like “http:/t.co/xxxxxxxx,” while users still see the text using “www.nytimes.com.”

By sending users to analytics servers first, the lawsuit claims Twitter could benefit by showing the New York Times (and other potential advertisers) where the source of the traffic is.

“The end result is that Twitter can negotiate better advertising rates,” says the lawsuit.

This interference represents a violation of the Electronic Communications Privacy Act and California’s privacy law, the lawsuit claims.

The lawsuit was filed on behalf of any Americans who have sent or received a direct message and seeks damages that would amount to about “$100 per day for each Twitter user whose privacy was violated.”

A Twitter spokesman responded to the lawsuit by simply saying: “We believe these claims are meritless and we intend to fight them.”

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