Analysis by: Marvelous Pelin
ALIASES:

Ransom.Yafcookie.Gen!c(AegisLab)

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • 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: 3,098,112 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 01 Mar 2017
Payload: Drops files, 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 files:

  • %User Temp%\fukjdJd1shjdhsjd2.tmp - contains the number of instances the malware was executed
  • {drive letter:}\test. log - contains the strings Status OK!
  • %User Temp%\3h88jdRdhsufjdJj3.tmp - list of encrypted files

(Note: %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp 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.)

Other Details

This Trojan does the following:

  • It avoids encrypting files with the following extensions:
    • .bat
    • .com
    • .dll
    • .exe
    • .ico
    • .inf
    • .ini
    • .log
    • .sys
    • .url
  • It adds the "YouAreFucked" string at the beginning of the encrypted files' binary .

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 13.252.07
FIRST VSAPI PATTERN DATE: 02 Mar 2017
VSAPI OPR PATTERN File: 13.253.00
VSAPI OPR PATTERN Date: 03 Mar 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

Restart in Safe Mode

[ Learn More ]

Step 4

Search and delete this file

[ 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.  
  • %User Temp%\fukjdJd1shjdhsjd2.tmp
  • %User Temp%\3h88jdRdhsufjdJj3.tmp
  • {drive letter:}\test. log

Step 5

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