The abrupt discontinuation of the popular open-source encryption software TrueCrypt has left its users puzzled.

Users looking to download the TrueCrypt program on Wednesday from its official website were greeted with an ominous message warning users that the encryption software was inherently insecure.

The warning message reads:

“WARNING: Using TrueCrypt is not secure as it may contain unfixed security issues.”

Following the initial warning message posted on the TrueCrypt site were instructions for migrating data from TrueCrypt to BitLocker, an encryption solution developed by Microsoft Corp. (NASDAQ:MSFT). According to TrueCrypt’s page, development behind the software ceased in May as Microsoft ended its support for Windows XP.

From TrueCrypt’s page:

“This page exists only to help migrate existing data encrypted by TrueCrypt.

The development of TrueCrypt was ended in May after Microsoft terminated support of Windows XP. Windows 8/7/Vista and later offer integrated support for encrypted disks and virtual disk images. Such integrated support is also available on other platforms (click here for more information). You should migrate any data encrypted by TrueCrypt to encrypted disks or virtual disk images supported on your platform.”

While alternative encryption solutions are available on Windows, Linux and Mac OSX, TrueCrypt was especially popular with users such as journalists for its hidden volume encryption feature, which created a hidden pocket of data within a standard TrueCrypt storage volume. This allowed its users some “plausible deniability” for that hidden data, even if they were forced to give up their password to the visible TrueCrypt encrypted storage volume.

Further adding to the mystery behind the abrupt change with TrueCrypt, the software has also been updated to provide only read-only access to data volumes created by previous versions of the encryption software.

The abrupt discontinuation comes at a time when TrueCrypt was in the process of a public security audit, which was partially completed in February 2014.

Several users disccusing the end of TrueCrypt on the Web have likened its sudden demise to the August 2013 shutdown of Lavabit, an encrypted email previously used by former National Security Agency contractor Edward Snowden, the whistleblower for the NSA's PRISM online spying program.