Analysis by: Arjun Bryan Baltazar
ALIASES:

Trojan-Ransom.Win32.Cryptor.bui (Kaspersky) , Trojan:Win32/Tiggre!rfn (Microsoft)

 PLATFORM:

Windows

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

  • Threat Type: Ransomware

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel: Downloaded from the Internet, Dropped by other malware

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 drops files as ransom note.

  TECHNICAL DETAILS

File Size: 828928 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 09 Jul 2018
Payload: Drops files

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.

Installation

This Ransomware drops the following files:

  • {Current Malware Path}\bat.bat
  • {Encrypted File Directory}\Notice.txt

It adds the following mutexes to ensure that only one of its copies runs at any one time:

  • gcc-shmem-tdm2-mutex_global_shmem
  • gcc-shmem-tdm2-global_lock_spinlock
  • gcc-shmem-tdm2-use_fc_key
  • gcc-shmem-tdm2-sjlj_once
  • gcc-shmem-tdm2-once_global_shmem
  • gcc-shmem-tdm2-once_obj_shmem
  • gcc-shmem-tdm2-_pthread_tls_once_shmem
  • gcc-shmem-tdm2-_pthread_tls_shmem
  • gcc-shmem-tdm2-mtx_pthr_locked_shmem
  • gcc-shmem-tdm2-mutex_global_static_shmem
  • gcc-shmem-tdm2-mxattr_recursive_shmem
  • gcc-shmem-tdm2-pthr_root_shmem
  • gcc-shmem-tdm2-idListCnt_shmem
  • gcc-shmem-tdm2-idListMax_shmem
  • gcc-shmem-tdm2-idList_shmem
  • gcc-shmem-tdm2-idListNextId_shmem
  • gcc-shmem-tdm2-fc_key
  • gcc-shmem-tdm2-_pthread_key_lock_shmem
  • gcc-shmem-tdm2-cond_locked_shmem_rwlock
  • gcc-shmem-tdm2-rwl_global_shmem
  • gcc-shmem-tdm2-_pthread_key_sch_shmem
  • gcc-shmem-tdm2-_pthread_key_max_shmem
  • gcc-shmem-tdm2-_pthread_key_dest_shmem

Other Details

This Ransomware does the following:

  • It deletes shadow copies by executing the following command:
    • vssadmin delete shadows /all /quiet
  • After encrypting the files it will drop and execute a bat file that will be used to delete itself
  • It encrypts files in all fixed, remote and removable drives.
  • Shows the following:

Ransomware Routine

This Ransomware avoids encrypting files found in the following folders:

  • C:\Windows

It appends the following extension to the file name of the encrypted files:

  • .zzz12

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

  • {Encrypted File Directory}\Notice.txt

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 14.384.01
FIRST VSAPI PATTERN DATE: 16 Jul 2018
VSAPI OPR PATTERN File: 14.385.0
VSAPI OPR PATTERN Date: 17 Jul 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

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.
  • {Current Malware Path}\bat.bat
  • {Encrypted File Directory}\Notice.txt

Step 5

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