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Google (s goog) sent a letter to FBI head Robert Mueller and Attorney General Eric Holder Tuesday requesting permission to disclose the number of times the federal government requests data on national security grounds, according to a blog post. Facebook (s fb) and Microsoft (s msft) have followed suit.

For now, the companies are prohibited from releasing such information.

It’s clearly a PR offensive on behalf of the web and software giants, hoping to distance themselves from revelations that the three companies and others have participated in the FBI and National Security Agency’s PRISM program first reported last week.

It’s still unclear just how the program gained access to external data and what participating companies have done to enable this sort of access. But regardless of that, the perception of complicity is something Google and the rest must fight. Whether or not the federal government complies with requests for more transparency almost doesn’t matter. The companies need to at least look like they want to shed light on their involvement and the extent of the data mining. And the letters achieve that goal.

Feature image courtesy of Shutterstock user ARTSILENSE.