When a computer hibernates (or enters a power-saving mode), the content of its system memory is written to a storage file on the hard drive. TrueCrypt cannot reliably prevent cached passwords, encryption keys, and the contents of sensitive files opened in RAM from being saved unencrypted to a hibernation storage file. Note that when you open a file stored on a TrueCrypt volume, for example, in a text editor, then the content of the file is stored unencrypted in RAM (and it may remain unencrypted in RAM until the computer is turned off). Also note that when a TrueCrypt volume is mounted, its master key is stored unencrypted in RAM. Therefore, we strongly recommend that you prevent or disable hibernation mode on your computer at least for each session during which you work with any sensitive data and during which you mount a TrueCrypt volume.

Note: If your system partition/drive is encrypted by TrueCrypt, the TrueCrypt driver automatically prevents Windows from hibernating the computer (for information on how to encrypt the system partition/drive, see the chapter System Encryption).