All read/write operations to the BoxCryptor Drive are decrypted/encrypted automatically and the plaintext data is then processed to the requesting application.
Example: You open an image in the BoxCryptor Drive with XnView
1) XnView sends (several) read requests to the BoxCryptor Drive
2) For each read request:
2.1) BoxCryptor reads the appropriate part of the encrypted file into the memory
2.2) BoxCryptor decrypts the data in memory
2.3) BoxCryptor returns the plaintext data to XnView in memory
3) XnView shows the image based on the plaintext data in memory which it received from BoxCryptor
So if you attach, move or copy a file outside of the BoxCryptor Drive, it will be decrypted and further processed in plaintext.