Analysis by: Wilbert Vidal


Ransom:Win32/GandCrab.A (Microsoft); Trojan.Ransom.Gandcrab (ALYac); Trojan-Ransom.GandCrab (A) (Emsisoft)




  • Threat Type: Ransomware

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes


This Ransomware arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It modifies the Internet Explorer Zone Settings.

It is capable of encrypting files in the affected system.

It drops files as ransom note.


File Size: 131,584 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 26 Jan 2018

Arrival Details

This Ransomware arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.


This Ransomware drops the following copies of itself into the affected system:

  • %Application Data%\Microsoft\{6 random character}.exe

(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.)

Autostart Technique

This Ransomware modifies the following registry entry(ies) to enable its automatic execution at every system startup:

{11 random characters} = %Application Data%\Microsoft\{6 random character}.exe

Web Browser Home Page and Search Page Modification

This Ransomware modifies the Internet Explorer Zone Settings.

Other Details

This Ransomware connects to the following URL(s) to get the affected system's IP address:


It connects to the following possibly malicious URL:

  • {BLOCKED}.{BLOCKED}.77.218

It performs DNS requests to the following sites:

  • a.{BLOCKED}

It is capable of encrypting files in the affected system.

Ransomware Routine

This Ransomware appends the following extension to the file name of the encrypted files:

  • .GDCB

It drops the following file(s) as ransom note:

  • {encrypted folder}\GDCB-DECRYPT.txt


Minimum Scan Engine: 9.850
VSAPI OPR PATTERN File: 13.929.00
VSAPI OPR PATTERN Date: 27 Jan 2018

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

[ Learn More ]

Step 4

Restore these modified registry values

[ Learn More ]

Important:Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this only if you know how to or you can seek your system administrator's help. You may also check out this Microsoft article first before modifying your computer's registry.

  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunOnce
    • {11 random characters} = %Application Data%\Microsoft\{6 random characters}.exe

Step 5

Search and delete these files

[ Learn More ]
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.
  • {encrypted folder}\GDCB-DECRYPT.txt

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as RANSOM_GANDCRAB.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.

Step 7

Restore encrypted files from backup.

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