Trojan.ZlobRisk Level 1: Very Low
Discovered: April 23, 2005
Updated: August 2, 2006 12:08:26 PM ZE9
Type: Trojan Horse
Infection Length: 18,364 bytes
Systems Affected: Windows 2000, Windows 95, Windows 98, Windows Me, Windows NT, Windows Server 2003, Windows XP
Trojan.Zlob is a back door Trojan that allows the remote attacker to perform various malicious actions on the compromised computer.
Note: Definitions prior to May 26, 2005 detect this threat as Trojan.Zhopa.
ProtectionVirus Definitions (LiveUpdate™ Weekly) April 27, 2005
Virus Definitions (Intelligent Updater) April 24, 2005
Threat AssessmentWildWild Level: Low
Number of Infections: 0 - 49
Number of Sites: 0 - 2
Geographical Distribution: Low
Threat Containment: Easy
Removal: Easy
DamageDamage Level: Medium
Releases Confidential Info: Sends system information to a remote attacker.
Compromises Security Settings: May download and execute remote files, incuding copies of itself.
DistributionDistribution Level: Low
TECHNICAL INFO:
When Trojan.Zlob is executed, it performs the following actions:
Copies itself as one of the following files:
%System%\msmsgs.exe
%System%\ld100.tmp
%System%\regperf.exe
Note: %System% is a variable that refers to the System folder. By default this is C:\Windows\System (Windows 95/98/Me), C:\Winnt\System32 (Windows NT/2000), or C:\Windows\System32 (Windows XP).
Adds the following value:
"Shell" = "Explorer.exe, msmsgs.exe"
to the registry subkey:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
so that the Trojan runs every time Windows starts.
Creates the following value:
"MSN Messenger" = "%System%\msmsgs.exe"
to the registry subkey:
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
so that the Trojan runs every time Windows starts.
Adds the following value:
"uuid" = "86c29b2f-3389-418b-9b47-c2b09b6abc07"
to the registry subkey:
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion
Adds one of the following values:
"wininet.dll" = "regperf.exe"
"notepad.exe" = "msmsgs.exe"
to the registry key
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer\Run
so that the Trojan runs when Windows starts or the user logs on.
Injects itself into the explorer.exe process.
Attempts to make HTTP connections to the following domains using different URLs, which allow the Trojan to ping, report it's status, and execute remote files:
vnp7s.net
zxserv0.com
dumpserv.com
Recommendations
Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":
Turn off and remove unneeded services. By default, many operating systems install auxiliary services that are not critical, such as an FTP server, telnet, and a Web server. These services are avenues of attack. If they are removed, blended threats have less avenues of attack and you have fewer services to maintain through patch updates.
If a blended threat exploits one or more network services, disable, or block access to, those services until a patch is applied.
Always keep your patch levels up-to-date, especially on computers that host public services and are accessible through the firewall, such as HTTP, FTP, mail, and DNS services (for example, all Windows-based computers should have the current Service Pack installed.). Additionally, please apply any security updates that are mentioned in this writeup, in trusted Security Bulletins, or on vendor Web sites.
Enforce a password policy. Complex passwords make it difficult to crack password files on compromised computers. This helps to prevent or limit damage when a computer is compromised.
Configure your email server to block or remove email that contains file attachments that are commonly used to spread viruses, such as .vbs, .bat, .exe, .pif and .scr files.
Isolate infected computers quickly to prevent further compromising your organization. Perform a forensic analysis and restore the computers using trusted media.
Train employees not to open attachments unless they are expecting them. Also, do not execute software that is downloaded from the Internet unless it has been scanned for viruses. Simply visiting a compromised Web site can cause infection if certain browser vulnerabilities are not patched.
REMOVAL - (Capt Crash inserts = LOL! ~ BUY the symantic antivirus - run the update - then run a scan.)
The following instructions pertain to all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.
Disable System Restore (Windows Me/XP).
Update the virus definitions.
Run a full system scan and delete all the files detected asTrojan.Zlob.
Delete any values added to the registry.
For specific details on each of these steps, read the following instructions.
1. To disable System Restore (Windows Me/XP)
If you are running Windows Me or Windows XP, we recommend that you temporarily turn off System Restore. Windows Me/XP uses this feature, which is enabled by default, to restore the files on your computer in case they become damaged. If a virus, worm, or Trojan infects a computer, System Restore may back up the virus, worm, or Trojan on the computer.
Windows prevents outside programs, including antivirus programs, from modifying System Restore. Therefore, antivirus programs or tools cannot remove threats in the System Restore folder. As a result, System Restore has the potential of restoring an infected file on your computer, even after you have cleaned the infected files from all the other locations.
Also, a virus scan may detect a threat in the System Restore folder even though you have removed the threat.
For instructions on how to turn off System Restore, read your Windows documentation, or one of the following articles:
How to disable or enable Windows Me System Restore
How to turn off or turn on Windows XP System Restore
Note: When you are completely finished with the removal procedure and are satisfied that the threat has been removed, reenable System Restore by following the instructions in the aforementioned documents.
For additional information, and an alternative to disabling Windows Me System Restore, see the Microsoft Knowledge Base article: Antivirus Tools Cannot Clean Infected Files in the _Restore Folder (Article ID: Q263455).
2. To update the virus definitions
Symantec Security Response fully tests all the virus definitions for quality assurance before they are posted to our servers. There are two ways to obtain the most recent virus definitions:
Running LiveUpdate, which is the easiest way to obtain virus definitions: These virus definitions are posted to the LiveUpdate servers once each week (usually on Wednesdays), unless there is a major virus outbreak. To determine whether definitions for this threat are available by LiveUpdate, refer to the document: Virus Definitions (LiveUpdate).
Downloading the definitions using the Intelligent Updater: The Intelligent Updater virus definitions are posted daily. You should download the definitions from the Symantec Security Response Web site and manually install them. To determine whether definitions for this threat are available by the Intelligent Updater, refer to the document: Virus Definitions (Intelligent Updater).
The latest Intelligent Updater virus definitions can be obtained here: Intelligent Updater virus definitions. For detailed instructions read the document: How to update virus definition files using the Intelligent Updater.
3. To scan for and delete the infected files
Start your Symantec antivirus program and make sure that it is configured to scan all the files. The following instructions pertain to all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.
For Norton AntiVirus consumer products: Read the document: How to configure Norton AntiVirus to scan all files.
For Symantec AntiVirus Enterprise products: Read the document: How to verify that a Symantec Corporate antivirus product is set to scan all files.
Run a full system scan.
If any files are detected as infected with Trojan.Zlob, click Delete.
Note: If your Symantec antivirus product reports that it cannot delete an infected file, Windows may be using the file. To fix this, run the scan in Safe mode. For instructions, read the document: How to start the computer in Safe Mode. Once you have restarted in Safe mode, run the scan again.
After the files are deleted, restart the computer in Normal mode and proceed with section 4.
Warning messages may be displayed when the computer is restarted, as the threat has not been fully removed at this point. Please ignore these messages and just click OK. These messages will not appear when the computer is restarted after the removal instructions have been fully completed. The messages displayed may be similar to the following:
Title: [File path]
Message body: Windows cannot find [file name]. Make sure you typed the name correctly, and then try again. To search for a file, click the Start button, and then click Search.
4. To delete the value from the registry
Important: Symantec strongly recommends that you back up the registry before making any changes to it. Incorrect changes to the registry can result in permanent data loss or corrupted files. Modify the specified subkeys only. For instructions refer to the document: How to make a backup of the Windows registry.
Click Start > Run.
Type regedit
Click OK.
Navigate to the following subkey:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
In the right pane, delete the value:
"Shell" = "Explorer.exe, msmsgs.exe" <NOTE = CAPTAIN CRASH adds = i f you delete the WRONG lines from the wrong panes - then you will abruptly KILL something on your computer. I did try a manual fix once and KILLED my OS - I described what I did to a tech savvy friend and he just LAUGHED! He ended up reading what he could off my dead drive from another computer and laboriously he pulle my files off - ran an antivirus to clean them and reimaged the original drive. It took several hours.>
Navigate to the following subkey:
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
In the right pane, delete the value:
"MSN Messenger" = "%System%\msmsgs.exe"
Navigate to the following subkey:
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion
In the right pane, delete the value:
"uuid" = "[random characters]"
Navigate to the following subkey:
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\policies\explorer\Run
In the right pane, delete the value:
"notepad.exe" = "msmsgs.exe"
Exit the Registry Editor.
Writeup By: Ka Chun Leung
