TROJ_FILECRYPT.B

January 10, 2015
 ALIASES:

Ransom-FSE!E37562312D33 (McAfee); Trojan.Win32.Generic!BT (Sunbelt); Trojan horse FileCryptor.QJ (AVG)

 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:

11,137,536 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

10 Jan 2015

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 copies of itself into the affected system:

  • %User Temp%\1c55103ac15cdbb26ffaa8118ce6e871.exe

(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.)

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
1c55103ac15cdbb26ffaa8118ce6e871 = "%User Temp%\1c55103ac15cdbb26ffaa8118ce6e871.exe"

Other System Modifications

This Trojan modifies the following registry entries:

HKEY_CURRENT_USER\Control Panel\Desktop
Wallpaper = "%User Temp%\4.tmp.bmp"

(Note: The default value data of the said registry entry is %Windows%\web\wallpaper\Bliss.bmp.)

HKEY_CURRENT_USER\Control Panel\Desktop
Wallpaper = "%User Temp%\D.tmp.bmp"

(Note: The default value data of the said registry entry is %Windows%\web\wallpaper\Bliss.bmp.)

HKEY_CURRENT_USER\Control Panel\Desktop
Wallpaper = "%User Temp%\10.tmp.bmp"

(Note: The default value data of the said registry entry is %Windows%\web\wallpaper\Bliss.bmp.)

HKEY_CURRENT_USER\Control Panel\Desktop
Wallpaper = "%User Temp%\13.tmp.bmp"

(Note: The default value data of the said registry entry is %Windows%\web\wallpaper\Bliss.bmp.)

HKEY_CURRENT_USER\Control Panel\Desktop
Wallpaper = "%User Temp%\16.tmp.bmp"

(Note: The default value data of the said registry entry is %Windows%\web\wallpaper\Bliss.bmp.)

HKEY_CURRENT_USER\Control Panel\Desktop
Wallpaper = "%User Temp%\19.tmp.bmp"

(Note: The default value data of the said registry entry is %Windows%\web\wallpaper\Bliss.bmp.)

HKEY_CURRENT_USER\Control Panel\Desktop
Wallpaper = "%User Temp%\1C.tmp.bmp"

(Note: The default value data of the said registry entry is %Windows%\web\wallpaper\Bliss.bmp.)

HKEY_CURRENT_USER\Control Panel\Desktop
Wallpaper = "%User Temp%\1F.tmp.bmp"

(Note: The default value data of the said registry entry is %Windows%\web\wallpaper\Bliss.bmp.)

HKEY_CURRENT_USER\Control Panel\Desktop
Wallpaper = "%User Temp%\22.tmp.bmp"

(Note: The default value data of the said registry entry is %Windows%\web\wallpaper\Bliss.bmp.)

HKEY_CURRENT_USER\Control Panel\Desktop
Wallpaper = "%User Temp%\25.tmp.bmp"

(Note: The default value data of the said registry entry is %Windows%\web\wallpaper\Bliss.bmp.)

HKEY_CURRENT_USER\Control Panel\Desktop
Wallpaper = "%User Temp%\28.tmp.bmp"

(Note: The default value data of the said registry entry is %Windows%\web\wallpaper\Bliss.bmp.)

HKEY_CURRENT_USER\Control Panel\Desktop
Wallpaper = "%User Temp%\2B.tmp.bmp"

(Note: The default value data of the said registry entry is %Windows%\web\wallpaper\Bliss.bmp.)

HKEY_CURRENT_USER\Control Panel\Desktop
Wallpaper = "%User Temp%\2E.tmp.bmp"

(Note: The default value data of the said registry entry is %Windows%\web\wallpaper\Bliss.bmp.)

HKEY_CURRENT_USER\Control Panel\Desktop
Wallpaper = "%User Temp%\31.tmp.bmp"

(Note: The default value data of the said registry entry is %Windows%\web\wallpaper\Bliss.bmp.)

HKEY_CURRENT_USER\Control Panel\Desktop
Wallpaper = "%User Temp%\34.tmp.bmp"

(Note: The default value data of the said registry entry is %Windows%\web\wallpaper\Bliss.bmp.)

HKEY_CURRENT_USER\Control Panel\Desktop
Wallpaper = "%User Temp%\37.tmp.bmp"

(Note: The default value data of the said registry entry is %Windows%\web\wallpaper\Bliss.bmp.)

HKEY_CURRENT_USER\Control Panel\Desktop
Wallpaper = "%User Temp%\3A.tmp.bmp"

(Note: The default value data of the said registry entry is %Windows%\web\wallpaper\Bliss.bmp.)

HKEY_CURRENT_USER\Control Panel\Desktop
Wallpaper = "%User Temp%\3D.tmp.bmp"

(Note: The default value data of the said registry entry is %Windows%\web\wallpaper\Bliss.bmp.)

HKEY_CURRENT_USER\Control Panel\Desktop
Wallpaper = "%User Temp%\40.tmp.bmp"

(Note: The default value data of the said registry entry is %Windows%\web\wallpaper\Bliss.bmp.)

Dropping Routine

This Trojan drops the following files:

  • %User Temp%\cd938e4

(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 connects to the following possibly malicious URL:

  • http://checkip.{BLOCKED}s.org
  • http://{BLOCKED}g4os3vcgy7.onion/DA9D24C42F7F49181F0BE75221B257E0/k.php?{random characters}
  • http://{BLOCKED}kf4j3pze3j.onion/DA9D24C42F7F49181F0BE75221B257E0/k.php?{random characters}
  • http://{BLOCKED}mgcpbgwumb.onion/DA9D24C42F7F49181F0BE75221B257E0/k.php?{random characters}
  • http://{BLOCKED}wns6p4caz5.onion/DA9D24C42F7F49181F0BE75221B257E0/k.php?{random characters}
  • http://{BLOCKED}tj7cfj5lls.onion/DA9D24C42F7F49181F0BE75221B257E0/k.php?{random characters}
  • http://{BLOCKED}43wxj6opsq.onion/DA9D24C42F7F49181F0BE75221B257E0/k.php?{random characters}
  • http://{BLOCKED}fzerdkla7p.onion/DA9D24C42F7F49181F0BE75221B257E0/k.php?{random characters}
  • http://{BLOCKED}hz7mhmdjy7.onion/DA9D24C42F7F49181F0BE75221B257E0/k.php?{random characters}
  • http://{BLOCKED}5bnmld5bnj.onion/DA9D24C42F7F49181F0BE75221B257E0/k.php?{random characters}
  • http://{BLOCKED}traexy62c4.onion/DA9D24C42F7F49181F0BE75221B257E0/k.php?{random characters}
  • http://{BLOCKED}5jn6jkie2p.onion/DA9D24C42F7F49181F0BE75221B257E0/k.php?{random characters}
  • http://{BLOCKED}zpbbloox6v.onion/DA9D24C42F7F49181F0BE75221B257E0/k.php?{random characters}
  • http://{BLOCKED}crxmxrymus.onion/DA9D24C42F7F49181F0BE75221B257E0/k.php?{random characters}
  • http://{BLOCKED}27zmmkkjap.onion/DA9D24C42F7F49181F0BE75221B257E0/k.php?{random characters}
  • http://{BLOCKED}c6lsodyrcw.onion/DA9D24C42F7F49181F0BE75221B257E0/k.php?{random characters}
  • http://{BLOCKED}j3knld7p5g.onion/DA9D24C42F7F49181F0BE75221B257E0/k.php?{random characters}
  • {BLOCKED}6.38.70
  • {BLOCKED}0.1

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.700

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

Restart in Safe Mode

[ Learn More ]

Step 3

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
    • 1c55103ac15cdbb26ffaa8118ce6e871 = "%User Temp%\1c55103ac15cdbb26ffaa8118ce6e871.exe"

Step 4

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_CURRENT_USER\Control Panel\Desktop
    • From: Wallpaper = "%User Temp%\4.tmp.bmp"
      To: Wallpaper = ""%Windows%\web\wallpaper\Bliss.bmp""
  • In HKEY_CURRENT_USER\Control Panel\Desktop
    • From: Wallpaper = "%User Temp%\D.tmp.bmp"
      To: Wallpaper = ""%Windows%\web\wallpaper\Bliss.bmp""
  • In HKEY_CURRENT_USER\Control Panel\Desktop
    • From: Wallpaper = "%User Temp%\10.tmp.bmp"
      To: Wallpaper = ""%Windows%\web\wallpaper\Bliss.bmp""
  • In HKEY_CURRENT_USER\Control Panel\Desktop
    • From: Wallpaper = "%User Temp%\13.tmp.bmp"
      To: Wallpaper = ""%Windows%\web\wallpaper\Bliss.bmp""
  • In HKEY_CURRENT_USER\Control Panel\Desktop
    • From: Wallpaper = "%User Temp%\16.tmp.bmp"
      To: Wallpaper = ""%Windows%\web\wallpaper\Bliss.bmp""
  • In HKEY_CURRENT_USER\Control Panel\Desktop
    • From: Wallpaper = "%User Temp%\19.tmp.bmp"
      To: Wallpaper = ""%Windows%\web\wallpaper\Bliss.bmp""
  • In HKEY_CURRENT_USER\Control Panel\Desktop
    • From: Wallpaper = "%User Temp%\1C.tmp.bmp"
      To: Wallpaper = ""%Windows%\web\wallpaper\Bliss.bmp""
  • In HKEY_CURRENT_USER\Control Panel\Desktop
    • From: Wallpaper = "%User Temp%\1F.tmp.bmp"
      To: Wallpaper = ""%Windows%\web\wallpaper\Bliss.bmp""
  • In HKEY_CURRENT_USER\Control Panel\Desktop
    • From: Wallpaper = "%User Temp%\22.tmp.bmp"
      To: Wallpaper = ""%Windows%\web\wallpaper\Bliss.bmp""
  • In HKEY_CURRENT_USER\Control Panel\Desktop
    • From: Wallpaper = "%User Temp%\25.tmp.bmp"
      To: Wallpaper = ""%Windows%\web\wallpaper\Bliss.bmp""
  • In HKEY_CURRENT_USER\Control Panel\Desktop
    • From: Wallpaper = "%User Temp%\28.tmp.bmp"
      To: Wallpaper = ""%Windows%\web\wallpaper\Bliss.bmp""
  • In HKEY_CURRENT_USER\Control Panel\Desktop
    • From: Wallpaper = "%User Temp%\2B.tmp.bmp"
      To: Wallpaper = ""%Windows%\web\wallpaper\Bliss.bmp""
  • In HKEY_CURRENT_USER\Control Panel\Desktop
    • From: Wallpaper = "%User Temp%\2E.tmp.bmp"
      To: Wallpaper = ""%Windows%\web\wallpaper\Bliss.bmp""
  • In HKEY_CURRENT_USER\Control Panel\Desktop
    • From: Wallpaper = "%User Temp%\31.tmp.bmp"
      To: Wallpaper = ""%Windows%\web\wallpaper\Bliss.bmp""
  • In HKEY_CURRENT_USER\Control Panel\Desktop
    • From: Wallpaper = "%User Temp%\34.tmp.bmp"
      To: Wallpaper = ""%Windows%\web\wallpaper\Bliss.bmp""
  • In HKEY_CURRENT_USER\Control Panel\Desktop
    • From: Wallpaper = "%User Temp%\37.tmp.bmp"
      To: Wallpaper = ""%Windows%\web\wallpaper\Bliss.bmp""
  • In HKEY_CURRENT_USER\Control Panel\Desktop
    • From: Wallpaper = "%User Temp%\3A.tmp.bmp"
      To: Wallpaper = ""%Windows%\web\wallpaper\Bliss.bmp""
  • In HKEY_CURRENT_USER\Control Panel\Desktop
    • From: Wallpaper = "%User Temp%\3D.tmp.bmp"
      To: Wallpaper = ""%Windows%\web\wallpaper\Bliss.bmp""
  • In HKEY_CURRENT_USER\Control Panel\Desktop
    • From: Wallpaper = "%User Temp%\40.tmp.bmp"
      To: Wallpaper = ""%Windows%\web\wallpaper\Bliss.bmp""

Step 5

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%\cd938e4

Step 6

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