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Ransom_CUTSOME.A

February 14, 2017
 Analysis by: Janus Agcaoili
 ALIASES:

Ransom.Crysis (Symantec), Win64/Filecoder.E (ESET-NOD32)

 PLATFORM:

Windows (x64)

 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:

Dropped by other malware, Downloaded from the Internet


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:

77,312 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

07 Feb 2017

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.

Other System Modifications

This Trojan adds the following registry entries as part of its installation routine:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
kingscott = "hehehehehehehe"

Other Details

This Trojan encrypts files with the following extensions:

  • All extensions except for the following:
    • .chm
    • .ini
    • .tmp
    • .log
    • .url
    • .lnk
    • .cmd
    • .bat
    • .scr
    • .msi
    • .sys
    • .dll
    • .exe

It renames encrypted files using the following names:

  • {original filename and path}.enc

It does the following:

  • It targets files to encrypt in the following directory:
    • C:\

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

13.206.07

FIRST VSAPI PATTERN DATE:

07 Feb 2017

VSAPI OPR PATTERN File:

13.207.00

VSAPI OPR PATTERN Date:

08 Feb 2017

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

Identify and terminate files detected as Ransom_CUTSOME.A

[ Learn More ]
  1. Windows Task Manager may not display all running processes. In this case, please use a third-party process viewer, preferably Process Explorer, to terminate the malware/grayware/spyware file. You may download the said tool here.
  2. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  3. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

Step 4

Delete this registry value

[ Learn More ]

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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • kingscott = "hehehehehehehe"

Step 5

Scan your computer with your Trend Micro product to delete files detected as Ransom_CUTSOME.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 6

Restore encrypted files from backup.


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