Microsoft security software detects and removes this threat.

This ransomware encrypts the files on your PC and directs you to a webpage with instructions on how to unlock them. It can ask you to make a payment using bitcoins.

The ransom or "lock" screen can use the name CryptoDefense or CryptoWall.

See the Win32/Crotwi family description for more information.

More information about ransomware can be found on our Ransomware page.

Find out ways that malware can get on your PC.

What to do now

Microsoft doesn’t recommend you pay the fine. There is no guarantee that paying the ransom will give you access to your files.

If you've already paid, see our ransomware page for help on what to do now.

Run antivirus or antimalware software

Use the following free Microsoft software to detect and remove this threat:

You should also run a full scan. A full scan might find hidden malware.

Advanced troubleshooting

To restore your PC, you might need to download and run Windows Defender Offline. See our advanced troubleshooting page for more help.

Get more help

You can also visit our advanced troubleshooting page or search the Microsoft virus and malware community for more help.

If you’re using Windows XP, see our Windows XP end of support page.

Threat behavior


This threat is an HTML page dropped by Ransom:Win32/Crowti.


This malware can encrypt the files on your PC using a public key. The files can be decrypted with a private key stored in a remote server.

Crowti uses the following file names for its ransom note, which contains instructions on how to decrypt your files:


The ransom note is launched after the malware is done encrypting files in the system.

We have observed it connect to the following URLs:


Analysis by: Vladimir Zubko


 The following can indicate that you have this threat on your PC:
  • You have these files:


Alert level: Severe
First detected by definition: 1.161.2295.0
Latest detected by definition: 1.211.847.0 and higher
First detected on: Nov 16, 2013
This entry was first published on: Nov 16, 2013
This entry was updated on: Oct 27, 2015

This threat is also detected as:
No known aliases