More than two dozen U.S. government websites should be urgently upgraded to use encryption, as whistleblowers are potentially at risk, according to the American Civil Liberties Union.

At least 29 websites that can be used for reporting abuse and fraud don't use encryption, the ACLU said in a letter sent on Tuesday to the U.S.'s top technology chief, CIO Tony Scott.

There has been a broad push recently to move websites to using SSL/TLS (secure sockets layer/transport security layer) encryption. Most e-commerce sites use SSL/TLS, but the case has grown stronger for its broader adoption because of a surge in state-sponsored espionage and cybercriminal activity.

The government plans to upgrade all of its websites within two years to use encryption, signified by "https" in a browser's URL bar. It prevents data that is exchanged between a computer and a website from being read if it is intercepted or tampered with during a man-in-the-middle attack.

The ACLU said that the timeline "is not soon enough for some sensitive sites," which it said included the Justice Department, Treasury Department and the Department of Homeland Security.

For example, the State Department has a page where people can report terrorism-related tips, but that information is not protected by encryption when sent, the ACLU wrote.

"When individuals use these official whistleblowing channels to report waste, fraud or abuse, the information they submit is transmitted insecurely over the Internet where it can be intercepted by others," ACLU wrote.

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