Edit: After half day, my wife’s Mac started having the same problem. I have then applied the solution that I found in the Apple
Virtual Memory Encryption Essential In Mac OS X
A part of the virtual memory on any system is the place where the contents of the system’s RAM is written to the hard disk which is specifically termed as a swapfile in order to make up some space for other productive purposes. As the system is operated by the user, the system starts loading the program and data into the RAM, which is similar to having the work placed on the top of the pile. As more and more items are being saved on the RAM, it starts getting cluttered up. In order to keep your work in an efficient manner, some free space must be freed up by transferring a few items onto the hard drive. This is the basic mechanism how virtual memory functions and Mac operating systems make extensive use of it in order to increase the performance of the RAM usage within the system and maintains the operations in a very smooth manner, especially if the RAM size is considerably slow.
The utilization of virtual memory is considered quite essential for an optimized performance of the system but, to make it work more efficiently, Ram contents are written to the desk’s drawers or hard drives. The contents of the RAM are mostly based on binary data via the programs in their running conditions. In addition to applications, RAM might hold temporary stored usernames, passwords and various other personal information. After this the information is transferred to the virtual memory where this is a possibility that anyone can scour the data stored in the virtual memory and retrieves it ultimately.
In order to encounter this probability, previous models of Mac OS X is offering the option the option of encrypting of files within the virtual memory, so that if the hard disk is removed for any reason then the data on the virtual memory will appear like garbled information which will be useless to all the Mac users. This option can be accessed by the Security system preferences. This option has been changed from for the purpose of keeping the data on virtual memory activated all time. Since, this aspect is considered as logically acceptable because of the feature of enhanced security, it might not have been accepted by some of the people because of the Lion’s support for whole-disk encryption with File Vault 2.
Not similar to the original File Vault, which has the feature of encrypting the users home directory. File Vault 2 encrypts the entire drive without letting the operating system making aware of it. A result of this would be that all the files in the File Vault 2 inclusive of data of the operating system, virtual memory will be encrypted automatically which creates a situation in which the requirement to activate the virtual memory encryption will be negated. Moreover, the users may also wonder whether the encryption of the virtual memory should be turned off in order to get any additional advantage that might be offered.
The issue roused up recently after the issuance of a posting namely Mac OS X hints. In the posting it was described as to how virtual memory encryption can be deactivated in the Lion OS X by putting in the below mentioned command within the terminal
sudo defaults write /Library/Preferences/com.apple.virtualMemory DisableEncryptedSwap -boolean yes
Thinking logically, disabling virtual memory encryption and depending upon the File Vault for the protection as well as the encryption of the data, only if the user has particular reasons to deactivate the virtual memory encryption that even with the activation of File Vault 2 onto the system, the activation of the virtual memory encryption is required. The only reason behind such an act is that of any third person has gained access to your hard drive when it was not locked, than the encryption feature of the virtual memory can be used to scan out all the potential data simply by inserting a below mentioned command onto the terminal box
sudo strings – /private/var/vm/SWAPFILE > ~/info.txt
Under this command, the SWAPFILE is replaced with the Mac system’s virtual memory files such as ‘swapfile0 or swapfile1′. It will read out it thoroughly and will dump out the text strings that are found within the data into the home directory called “info.txt”
Concluding, it can be said that the virtual memory possess numerous security advantages because of which it has an edge, so, until and unless there is a grave need to disable them, it is clearly recommended to keep them active.