TROJ_KRYPTK.SMM
Windows 2000, Windows XP, Windows Server 2003
Threat Type: Trojan
Destructiveness: No
Encrypted: Yes
In the wild: Yes
OVERVIEW
This Trojan arrives as an attachment to email messages spammed by other malware/grayware or malicious users. It may be downloaded by other malware/grayware/spyware from remote sites. It may be dropped by other malware. It may be unknowingly downloaded by a user while visiting malicious websites.
TECHNICAL DETAILS
Varies
EXE
Yes
08 Mar 2011
Arrival Details
This Trojan arrives as an attachment to email messages spammed by other malware/grayware or malicious users.
It may be downloaded by other malware/grayware/spyware from remote sites.
It may be dropped by other malware.
It may be unknowingly downloaded by a user while visiting malicious websites.
Installation
This Trojan drops the following non-malicious files:
- %System%\lowsec\local.ds
- %System%\lowsec\user.ds
(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)
It drops the following copies of itself into the affected system:
- %System%\sdra64.exe
(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)
It injects itself into the following processes running in the affected system's memory:
- SVCHOST.EXE
- WINLOGON.EXE
It creates the following folders:
- %System%\lowsec
(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)
Autostart Technique
This Trojan modifies the following registry entry(ies) to enable its automatic execution at every system startup:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Userinit = "%System%\userinit.exe, %System%\sdra64.exe,"
(Note: The default value data of the said registry entry is %System%\userinit.exe, .)
Other System Modifications
This Trojan adds the following registry entries as part of its installation routine:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Network
UID = "{Computer name}_{Random numbers}"
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile
EnableFirewall = "0"
SOLUTION
8.900
7.885.00
08 Mar 2011
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_KRYPTK.SMM using either the Startup Disk or Recovery Console
Step 3
Restore these modified registry values
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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
- From: Userinit = %System%\userinit.exe, %System%\sdra64.exe,
To: Userinit = %System%\userinit.exe,
- From: Userinit = %System%\userinit.exe, %System%\sdra64.exe,
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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Network
- UID = {Computer name}_{Random numbers}
- UID = {Computer name}_{Random numbers}
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile
- EnableFirewall = 0
- EnableFirewall = 0
Step 5
Search and delete these folders
Step 6
Scan your computer with your Trend Micro product to delete files detected as TROJ_KRYPTK.SMM. 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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