BitStak targets Windows OS and the method of distribution is currently unknown. Once executed, BitStak encrypts files in the following folders: Program Files, Program Files (x86), Documents, Downloads, Videos, Music, Pictures, as well as those on the Desktop and within mapped network drives. During the encryption process, this variant renames each affected file and folder with a random letter combination and appends all encrypted files with the extension .bitstak. BitStak demands a ransom payment of 0.07867 Bitcoin and threatens to delete files if payment is not received within three days.

  • Bleeping Computer provides more information about BitStak here.
  • Bleeping Computer also provides a free decryption tool for BitStack here.

One example of the BitStak variant. Image Source: Bleeping Computer