TROJ_CRYPWALL.YR
Ransom:Win32/Crowti.D (Microsoft), Trojan-Ransom.Win32.Blocker.fval (Kaspersky)
Windows
Threat Type: Trojan
Destructiveness: No
Encrypted: No
In the wild: Yes
OVERVIEW
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.
It connects to certain websites to send and receive information.
TECHNICAL DETAILS
163696 bytes
EXE
Yes
30 Sep 2014
Steals information, Encrypts files, Drops 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 adds the following folders:
- %System Root%\{7 characters from UID}
(Note: %System Root% is the Windows root folder, where it usually is C:\ on all Windows operating system versions.)
It drops the following files:
- %User Startup%\DECRYPT_INSTRUCTION.TXT
- %User Startup%\DECRYPT_INSTRUCTION.HTML
- %User Startup%\DECRYPT_INSTRUCTION.URL
(Note: %User Startup% is the current user's Startup folder, which is usually C:\Windows\Profiles\{user name}\Start Menu\Programs\Startup on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Start Menu\Programs\Startup on Windows NT, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup.)
It drops and executes the following files:
- %Desktop%\DECRYPT_INSTRUCTION.TXT
- %Desktop%\DECRYPT_INSTRUCTION.HTML
- %Desktop%\DECRYPT_INSTRUCTION.URL
(Note: %Desktop% is the desktop folder, where it usually is C:\Documents and Settings\{user name}\Desktop in Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\Desktop in 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.)
It drops the following copies of itself into the affected system:
- %System Root%\{7 characters from UID}\{7 characters from UID}.exe
- %Application Data%\{7 characters from UID}.exe
- %User Startup%\{7 characters from UID}.exe
(Note: %System Root% is the Windows root folder, where it usually is C:\ on all Windows operating system versions.. %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming 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.. %User Startup% is the current user's Startup folder, which is usually C:\Windows\Profiles\{user name}\Start Menu\Programs\Startup on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Start Menu\Programs\Startup on Windows NT, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup.)
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
{7characters from UID} = "%Application Data%\{7 characters from UID}.exe"
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{6 characters from UID} = "%System Root%\{7 characters from UID}\{7 characters from UID}.exe"
Other System Modifications
This Trojan adds the following registry keys:
HKEY_CURRENT_USER\Software\{UID}
HKEY_CURRENT_USER\Software\{UID}\
{random key}
It adds the following registry entries:
HKEY_CURRENT_USER\Software\{UID}\
{random key}
{Path and File name of encrypted file} = "{hex values}"
Information Theft
This Trojan gathers the following data:
- Unique Identifier (UID)
Other Details
This Trojan connects to the following website to send and receive information:
- http://{BLOCKED}ntin.com/{random generated value}
It encrypts files with the following extensions:
- .aif
- .aifc
- .aiff
- .asf
- .asx
- .au
- .bas
- .bat
- .bmp
- .cmd
- .com
- .dib
- .doc
- .dot
- .dvr-ms
- .emf
- .exe
- .gif
- .hta
- .htm
- .html
- .ico
- .jfif
- .jpe
- .jpeg
- .jpg
- .m1v
- .m3u
- .mid
- .midi
- .mp2
- .mp2v
- .mp3
- .mpa
- .mpe
- .mpeg
- .mpg
- .mpv2
- .msi
- .pif
- .png
- .pot
- .pps
- .ppt
- .reg
- .rle
- .rmi
- .rtf
- .scr
- .snd
- .tif
- .tiff
- .vb
- .wav
- .wm
- .wma
- .wmf
- .wmv
- .wmx
- .wvx
- .xls
- .xlt
- .xlw
- .xml
- .zip
NOTES:
It drops the following files to all folders after encryption:
- DECRYPT_INSTRUCTION.TXT
- DECRYPT_INSTRUCTION.HTML
- DECRYPT_INSTRUCTION.URL
It opens the dropped file DECRYPT_INSTRUCTION.HTML which contains the ransom note:
It demands payment for using decryption service:
It deletes its dropped copies and the added AUTORUN registry entries after encryption is successful.
SOLUTION
9.700
11.182.05
30 Sep 2014
11.183.00
30 Sep 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
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
Step 4
Delete this registry value
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
- {7characters from UID} = "%Application Data%\{7 characters from UID}.exe"
- {7characters from UID} = "%Application Data%\{7 characters from UID}.exe"
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
- {6 characters from UID} = "%System Root%\{7 characters from UID}\{7 characters from UID}.exe"
- {6 characters from UID} = "%System Root%\{7 characters from UID}\{7 characters from UID}.exe"
Step 5
Delete this registry key
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
- {UID}
- {UID}
Step 6
Search and delete this folder
- %System Root%\{7 characters from UID}
Step 7
Search and delete this file
- DECRYPT_INSTRUCTION.HTML
- DECRYPT_INSTRUCTION.TXT
- DECRYPT_INSTRUCTION.URL
Step 8
Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_CRYPWALL.YR. 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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