TROJ_RANSOM.USRI

 Analysis by: Adrian Cofreros

 ALIASES:

Trojan-Ransom.Win32.Blocker.droa(Kaspersky),a variant of Win32/Kryptik.BUSQ trojan,Trojan horse Crypt2.CMZR(AVG)

 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:

  • 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.

It deletes the initially executed copy of itself.

  TECHNICAL DETAILS

File Size:

322,560 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

24 Feb 2014

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:

  • {different locations}\BitCrypt.txt
  • %Application Data%\bitcrypt.ccw

(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Roaming on Windows Vista and 7.)

It drops the following copies of itself into the affected system:

  • %Application Data%\{random file name}.exe

(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Roaming on Windows Vista and 7.)

Autostart Technique

This Trojan adds the following registry entries to enable its automatic execution at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Bitcomint = %Application Data%\{random file name}.exe

Other System Modifications

This Trojan deletes the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Control\SafeBoot\Network

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Control\SafeBoot\Minimal

Other Details

This Trojan deletes the initially executed copy of itself

NOTES:

It may encrypt files.

  SOLUTION

Minimum Scan Engine:

9.700

FIRST VSAPI PATTERN FILE:

10.628.03

FIRST VSAPI PATTERN DATE:

25 Feb 2014

VSAPI OPR PATTERN File:

10.629.00

VSAPI OPR PATTERN Date:

26 Feb 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.USRI

Step 3

Identify and delete files detected as TROJ_RANSOM.USRI using the Recovery Console

[ Learn More ]

Step 4

Search and delete these files

[ Learn More ]
There may be some component 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.
  • {different locations}\BitCrypt.txt
  • %Application Data%\bitcrypt.ccw

Step 5

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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • Bitcomint = %Application Data%\{random file name}.exe

Step 6

Scan your computer with your Trend Micro product to delete files detected as TROJ_RANSOM.USRI. 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 7

Restore these deleted registry keys/values from backup

*Note: Only Microsoft-related keys/values will be restored. If the malware/grayware also deleted registry keys/values related to programs that are not from Microsoft, please reinstall those programs on your computer.

  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SafeBoot
    • Network
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SafeBoot
    • Minimal


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