TROJ_LETHIC.WRN
Trojan:Win32/Lethic.B (Microsoft); Backdoor.Win32.Azbreg.zwv (Kaspersky); Mal/EncPk-AKA (Sophos); Trojan horse Inject2.AJMD (AVG)
Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)
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
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:
- %System Root%\RECYCLER\S-1-5-21-0243556031-888888379-781863308-13456730\fa22251.exe
(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)
It creates the following folders:
- %System Root%\RECYCLER
- %System Root%\RECYCLER\S-1-5-21-0243556031-888888379-781863308-13456730
(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)
Autostart Technique
This Trojan adds the following registry entries to enable its automatic execution at every system startup:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Taskman = "%System Root%\RECYCLER\S-1-5-21-0243556031-888888379-781863308-13456730\fa22251.exe"
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
d12225a1 = "%System Root%\RECYCLER\S-1-5-21-0243556031-888888379-781863308-13456730\fa22251.exe"
Other System Modifications
This Trojan deletes the following files:
- %System Root%\RECYCLER\S-1-5-21-0243556031-888888379-781863308-13456730\fa22251.exe
(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)
It adds the following registry entries:
HKEY_CURRENT_USER\Software\Microsoft\
Windows NT\CurrentVersion\Winlogon
Shell = "{random characters}"
Dropping Routine
This Trojan drops the following files:
- %System Root%\RECYCLER\S-1-5-21-0243556031-888888379-781863308-13456730\Desktop.ini
(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)
Other Details
This Trojan connects to the following possibly malicious URL:
- {BLOCKED}.6.68
- {BLOCKED}3.0.67
This report is generated via an automated analysis system.
SOLUTION
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
Identify and delete files detected as TROJ_LETHIC.WRN using either the Startup Disk or Recovery Console
Step 3
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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
- Taskman = "%System Root%\RECYCLER\S-1-5-21-0243556031-888888379-781863308-13456730\fa22251.exe"
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
- d12225a1 = "%System Root%\RECYCLER\S-1-5-21-0243556031-888888379-781863308-13456730\fa22251.exe"
- In HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Winlogon
- Shell = "{random characters}"
Step 4
Search and delete this file
- %System Root%\RECYCLER\S-1-5-21-0243556031-888888379-781863308-13456730\Desktop.ini
Step 5
Search and delete these folders
- %System Root%\RECYCLER
- %System Root%\RECYCLER\S-1-5-21-0243556031-888888379-781863308-13456730
Step 6
Scan your computer with your Trend Micro product to delete files detected as TROJ_LETHIC.WRN. 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 this file from backup only Microsoft-related files will be restored. If this malware/grayware also deleted files related to programs that are not from Microsoft, please reinstall those programs on you computer again.
- %System Root%\RECYCLER\S-1-5-21-0243556031-888888379-781863308-13456730\fa22251.exe
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