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Ransom_CRYPTESLA.YUYAKM

April 12, 2016
 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW


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:

186,880 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

12 Apr 2016

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.

Other System Modifications

This Trojan modifies the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Dfrg\BootOptimizeFunction
LcnStartLocation = "1632602"

(Note: The default value data of the said registry entry is 0.)

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Dfrg\BootOptimizeFunction
LcnEndLocation = "1736984"

(Note: The default value data of the said registry entry is 0.)

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Dfrg\BootOptimizeFunction
OptimizeError = "Insufficient free space"

(Note: The default value data of the said registry entry is Not Run.)

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Dfrg\BootOptimizeFunction
OptimizeComplete = "No"

(Note: The default value data of the said registry entry is No.)

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.8

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

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_LOCAL_MACHINE\SOFTWARE\Microsoft\Dfrg\BootOptimizeFunction
    • From: LcnStartLocation = "1632602"
      To: LcnStartLocation = ""0""
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Dfrg\BootOptimizeFunction
    • From: LcnEndLocation = "1736984"
      To: LcnEndLocation = ""0""
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Dfrg\BootOptimizeFunction
    • From: OptimizeError = "Insufficient free space"
      To: OptimizeError = ""Not Run""
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Dfrg\BootOptimizeFunction
    • From: OptimizeComplete = "No"
      To: OptimizeComplete = ""No""

Step 3

Scan your computer with your Trend Micro product to delete files detected as Ransom_CRYPTESLA.YUYAKM. 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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