This ransomware is one of the few ransomware families that is capable of spreading on its own. It drops a copy of itself in removable drives, making use of USBs a risky practice. Another notable feature of this ransomware is that it runs on Windows XP 64-bit and more recent versions of Windows such as Windows 7 and 8. It asks for an initial 1.2 bitcoin ($500) payment, which increases to 5 bitcoins ($2,200) after four days of non-payment.
To get a one-glance comprehensive view of the behavior of this Worm, refer to the Threat Diagram shown below.

This worm arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.
It connects to certain websites to send and receive information. However, as of this writing, the said sites are inaccessible.
Arrival Details
This worm arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.
Installation
This worm drops the following copies of itself into the affected system:
- %Application Data%\zcrypt.exe -> attributes are set to Hidden and System
(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)
It drops the following files:
- %Application Data%\btc.addr -> Bitcoin Address
- %Application Data%\cid.ztxt -> contains the victim's ID
- %Application Data%\public.key -> public key
- %Application Data%\private.key -> private key
(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)
It adds the following mutexes to ensure that only one of its copies runs at any one time:
Autostart Technique
This worm adds the following registry entries to enable its automatic execution at every system startup:
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
zcrypt = {path of the executed malware}
It drops the following files:
- {Removable Drive Letter}:\autorun.inf
It drops the following file(s) in the Windows Startup folder to enable its automatic execution at every system startup:
- %User Startup%\zcrypt.lnk -> Shortcut file for the executed malware
(Note: %User Startup% is the current user's Startup folder, which is usually C:\Documents and Settings\{user}\Start Menu\Programs\Startup on Windows 2000 and XP, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup on Windows Vista, 7, and 8.)
Propagation
This worm drops the following copy(ies) of itself in all removable drives:
- {Removable Drive Letter}:\System.exe -> attribute is set to Hidden
Other Details
This worm connects to the following website to send and receive information:
- http://{BLOCKED}rewq.ml/rsa/rsa.php?computerid={victim ID}&public=1
It encrypts files with the following extensions:
- .3fr
- .accdb
- .apk
- .arw
- .aspx
- .avi
- .bak
- .bay
- .bmp
- .cdr
- .cer
- .cgi
- .class
- .cpp
- .cr2
- .crt
- .crw
- .dbf
- .dcr
- .der
- .dng
- .doc
- .docx
- .dwg
- .dxg
- .emlx
- .eps
- .erf
- .gz
- .html
- .indd
- .jar
- .java
- .jpeg
- .jpg
- .jsp
- .kdc
- .log
- .mdb
- .mdf
- .mef
- .mp4
- .mpeg
- .msg
- .nrw
- .odb
- .odp
- .ods
- .odt
- .orf
- .p12
- .p7b
- .p7c
- .pdb
- .pdd
- .pdf
- .pef
- .pem
- .pfx
- .php
- .png
- .ppt
- .pptx
- .psd
- .pst
- .ptx
- .r3d
- .raf
- .raw
- .rtf
- .rw2
- .rwl
- .sav
- .sql
- .srf
- .srw
- .swf
- .tar
- .tar
- .txt
- .vcf
- .wb2
- .wmv
- .wpd
- .xls
- .xlsx
- .xml
- .zip
It renames encrypted files using the following names:
- {original filename}.zcrypt
It does the following:
- Encrypts files in removable drive
However, as of this writing, the said sites are inaccessible.
NOTES:
The ransom note is dropped as How to decrypt your files.html, once it is successfully connected with its C&C server.

Step 1
Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.
Step 2
Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.
Step 3
Restart in Safe Mode
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To restart in Safe Mode:
• For Windows 2000 users
- Restart your computer.
- Press F8 when you see the Starting Windows bar at the bottom of the screen.
- Choose the Safe Mode option from the Windows Advanced Options menu then press Enter.
• For Windows XP users
- Restart your computer.
- Press F8 after the Power-On Self Test (POST) routine is done. If the Windows Advanced Options menu does not appear, try restarting then pressing F8 several times when the POST screen appears.
- Choose the Safe Mode option from the Windows Advanced Options menu then press Enter.
• For Windows Server 2003 users
- Restart your computer.
- Press F8 after Windows starts up. If the Windows Advanced Options menu does not appear, try restarting again and pressing F8 several times afterward.
- On the Windows Advanced Option menu, use the arrow keys to select Safe Mode then press Enter.
• For Windows Vista, Windows 7, and Windows Server 2008 users
- Restart your computer.
- Press F8 after the Power-On Self Test (POST) routine is done. If the Advanced Boot Options menu does not appear, try restarting and then pressing F8 several times after the POST screen is displayed.
- On the Advanced Boot Options menu, use the arrow keys to select the Safe Mode option, and then press Enter.
• For Windows 8, Windows 8.1, and Windows Server 2012 users
- Access the Charms bar by moving your mouse pointer to the upper right corner of the screen.
- Move your mouse pointer down and click Settings>Change your PC Settings.
- In the left panel, click General.
- In the right panel, scroll down to the bottom to find the Advanced startup section, then click the Restart now button and wait for the system to restart.
- In the Advanced Startup menu, click Troubleshoot>Advanced Options>Startup Settings>Restart and wait for the system to restart.
- In the Startup Settings menu, press 4 to enable safe mode.
Step 4
Delete this registry value
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Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
- zcrypt = {path of the executed malware}
To delete the registry value this malware created:
- Open Registry Editor. To do this:
» For Windows 2000, Windows XP, and Windows Server 2003 users, click Start>Run, type regedit in the text box provided, and then press Enter.
» For Windows Vista, Windows 7, and Windows Server 2008 users, click the Start button, type regedit in the Search input field then press Enter.
» For Windows 8, Windows 8.1, and Windows Server 2012 users, right-click on the lower left corner of the screen, click Run, type regedit in the text box provided, and then press Enter. - In the left panel of the Registry Editor window, double-click the following:
HKEY_CURRENT_USER>Software>Microsoft>Windows>CurrentVersion>Run - In the right panel, locate and delete the entry:
zcrypt = {path of the executed malware} - Close Registry Editor.
Step 5
Remove malware/grayware files dropped/downloaded by RANSOM_ZCRYPT.A. (Note: Please skip this step if the threats listed below have already been removed.)
Step 6
Search and delete these files
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There may be some files that are hidden. Please make sure you check the
Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.
- %Application Data%\zcrypt.exe
- %Application Data%\cid.ztxt
- %Application Data%\public.key
- %Application Data%\private.key
- %Application Data%\btc.addr
- %User Startup%\zcrypt.lnk
- {Removable Drive Letter}:\autorun.inf
- {Removable Drive Letter}:\System.exe
- How to decrypt your files.html
To delete malware/grayware files:
For Windows 2000, Windows XP, and Windows Server 2003:
- Right-click Start then click Search....
- In the File name* input box, type
- %Application Data%\zcrypt.exe
- %Application Data%\cid.ztxt
- %Application Data%\public.key
- %Application Data%\private.key
- %Application Data%\btc.addr
- %User Startup%\zcrypt.lnk
- {Removable Drive Letter}:\autorun.inf
- {Removable Drive Letter}:\System.exe
- How to decrypt your files.html
- In the Look In drop-down list, select My Computer then press Enter.
- Once located, select the file then press SHIFT+DELETE to delete it.
- Repeat the said steps for all files listed.
*Note: The file name input box title varies depending on the Windows version (e.g. Search for files or folders named or All or part of the file name.).
For Windows Vista, Windows 7, Windows Server 2008, Windows 8, Windows 8.1, and Windows Server 2012:
- Open a Windows Explorer window.
- For Windows Vista, 7, and Server 2008 users, click Start>Computer.
- For Windows 8, 8.1, and Server 2012 users, right-click on the lower left corner of the screen, then click File Explorer.
- In the Search Computer/This PC input box, type:
- %Application Data%\zcrypt.exe
- %Application Data%\cid.ztxt
- %Application Data%\public.key
- %Application Data%\private.key
- %Application Data%\btc.addr
- %User Startup%\zcrypt.lnk
- {Removable Drive Letter}:\autorun.inf
- {Removable Drive Letter}:\System.exe
- How to decrypt your files.html
- Once located, select the file then press SHIFT+DELETE to delete it.
- Repeat the said steps for all files listed.
*Note: Read the following Microsoft page if these steps do not work on Windows 7.
Step 7
Restart in normal mode and scan your computer with your Trend Micro product for files detected as RANSOM_ZCRYPT.A. If the detected files have already been cleaned, deleted, or quarantined by your Trend Micro product, no further step is required. You may opt to simply delete the quarantined files. Please check this Knowledge Base page for more information.
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