TROJ_INJECTO.AEH
Windows 2000, Windows XP, Windows Server 2003
![](/vinfo/imgFiles/legend.jpg)
Threat Type: Trojan
Destructiveness: No
Encrypted:
In the wild: Yes
OVERVIEW
This Trojan may be dropped by other malware. It may be unknowingly downloaded by a user while visiting malicious websites.
TECHNICAL DETAILS
Arrival Details
This Trojan may be dropped by other malware.
It may be unknowingly downloaded by a user while visiting malicious websites.
Installation
This Trojan drops the following files:
- %User Profile%\ss.exe
- %User Profile%\uz.dat
(Note: %User Profile% is the current user's profile folder, which is usually C:\Windows\Profiles\{user name} on Windows 98 and ME, C:\WINNT\Profiles\{user name} on Windows NT, and C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003.)
It drops the following copies of itself into the affected system:
- %System%\crrss.exe
- %User Profile%\winlogon.exe
(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.. %User Profile% is the current user's profile folder, which is usually C:\Windows\Profiles\{user name} on Windows 98 and ME, C:\WINNT\Profiles\{user name} on Windows NT, and C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003.)
Autostart Technique
This Trojan adds the following registry entries to enable its automatic execution at every system startup:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
crrss = "%System%\crrss.exe"
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
winlogon = "%User Profile%\winlogon.exe"
It modifies the following registry entry(ies) to enable its automatic execution at every system startup:
HKEY_CURRENT_USER\Software\Microsoft\
Windows NT\CurrentVersion\Winlogon
shell = "explorer.exe "%User Profile%\winlogon.exe""
(Note: The default value data of the said registry entry is "explorer.exe".)
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Userinit = "%System%\userinit.exe,%System%\crrss.exe"
(Note: The default value data of the said registry entry is "%System%\userinit.exe".)
Other Details
This Trojan connects to the following possibly malicious URL:
- {BLOCKED}.{BLOCKED}.36.246
SOLUTION
Step 1
For Windows XP and Windows Server 2003 users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.
Step 2
Restart in Safe Mode
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\CurrentVersion\Run
- crrss = "%System%\crrss.exe"
- crrss = "%System%\crrss.exe"
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
- winlogon = "%User Profile%\winlogon.exe"
- winlogon = "%User Profile%\winlogon.exe"
Step 4
Restore this modified 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 NT\CurrentVersion\Winlogon
- From: shell = "explorer.exe "%User Profile%\winlogon.exe""
To: shell = "explorer.exe"
- From: shell = "explorer.exe "%User Profile%\winlogon.exe""
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\Userinit
- From: Userinit = "%System%\userinit.exe,%System%\crrss.exe"
To: Userinit = "%System%\userinit.exe"
- From: Userinit = "%System%\userinit.exe,%System%\crrss.exe"
Step 5
Search and delete these files
- %User Profile%\ss.exe
- %User Profile%\uz.dat
Step 6
Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_INJECTO.AEH. 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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