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TROJ_RANSOM.CRDA

January 14, 2014
 Analysis by: Nikko Tamana
 ALIASES:

Trojan.Ransomcrypt (Norton)

 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:
 INFORMATION EXPOSURE:

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Downloaded from the Internet, Dropped by other malware

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

  TECHNICAL DETAILS

File Size:

666,112 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

10 Jan 2013

Payload:

Encrypts files

Arrival Details

This Trojan 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 Trojan drops the following file(s)/component(s):

  • {malware path}\privkey.bin - Stores the generated private RSA key
  • {malware path}\pubkey.bin - Stores the generated public RSA key
  • {malware path}\cryptedcount.txt - Lists count of encrypted files
  • {malware path}\countdown.txt

NOTES:

This Trojan avoids encrypting files with the following file extensions:

  • .RANS
  • .EXE
  • .DLL
  • .INI
  • .VXD
  • .DRV

It avoids encrypting files/directory with the following strings in their file name/folder name:

  • privkey.bin
  • pubkey.bin
  • countdown.txt
  • cryptedcount.txt
  • $Recycle.Bin

It saves the encrypted files using .rans as its file extension.

It searches for files to encrypt in fixed drives and remote (network) drives.

It sends the generated RSA keys to its C&C server.

It has anti-debugging capabilities.

  SOLUTION

Minimum Scan Engine:

9.700

FIRST VSAPI PATTERN FILE:

10.532.08

FIRST VSAPI PATTERN DATE:

10 Jan 2014

VSAPI OPR PATTERN File:

10.533.00

VSAPI OPR PATTERN Date:

11 Jan 2014

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

Scan your computer with your Trend Micro product and note files detected as TROJ_RANSOM.CRDA

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

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.
  • {malware path}\privkey.bin
  • {malware path}\pubkey.bin
  • {malware path}\countdown.txt
  • {malware path}\cryptedcount.txt

Step 5

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