Alert level

Trojan:Win32/Clort.A.dr


Encyclopedia entry
Updated: Nov 05, 2008  |  Published: Nov 05, 2008

Aliases
  • Trojan.Gimmiv-8 (Clam AV)
  • W32/Ristix.A (Authentium (Command))
  • MULDROP.Trojan (Dr.Web)
  • variant of Win32/Exploit.MS08-067.A (ESET)
  • New Downloader (McAfee)
  • Troj/Gimmiv-B (Sophos)

Alert Level (?)
Severe

Antimalware protection details
Microsoft recommends that you download the latest definitions to get protected.
Detection last updated:
Definition: 1.47.377.0
Released: Nov 15, 2008 		Detection initially created:
Definition: 1.45.1419.0
Released: Nov 05, 2008

Summary

Trojan:Win32/Clort.A.dr is a trojan that drops a trojan that exploits computers that have not applied Security Bulletin MS08-067.

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Symptoms

There are no common symptoms associated with this threat. Alert notifications from installed antivirus software may be the only symptom(s).

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Technical Information (Analysis)

Trojan:Win32/Clort.A.dr is a trojan that drops a trojan that exploits computers that have not applied Security Bulletin MS08-067.
Installation
In the wild, this trojan may exist as a file named 'MS08067a.exe'. When executed, it drops two executables:
 
%TEMP%\winlogon.exe - identified as Trojan:Win32/Clort.A
%TEMP%\svchost.exe - identified as Trojan:Win32/Clort.A!exploit
 
Win32/Clort.A.dr then executes 'winlogon.exe'.
 
Payload
Launches MS08-067 Attack
When Trojan:Win32/Clort.A is executed, it creates a mutex named ‘2008-MS08-067_TEST’ and exits if it already exists. This trojan connects to a remote site to retrieve target information, or IP address range data for the trojan to attack. The data is retrieved from the domain address 'gsinvest.gov.cn/*******/VoteModiy.asp'.
 
Next, Win32/Clort.A executes %TEMP%\svchost.exe, attacking IP addresses provided by text from the page 'VoteModify.asp'. It tries to connect to port 139, and if successful, launches
 
%TEMP%\svchost.exe <IP address>
 
The attack attempts to locate vulnerable computers that have not applied Security Bulletin MS08-067.
 
Downloads Other Malware
If a target computer is exploited, Win32/Clort.A!exploit executes shell code that instructs the target to download TrojanDownloader:Win32/VB.CJ from the domain 'dabao8.net' as a file named 'cc.exe'. The downloaded trojan is then run.
 
Win32/VB.CJ is a trojan that downloads other malware. When run, it attempts to download TrojanDownloader:Win32/VB.CQ from the domain 'nowbt.net' as a file named 'cpa.exe'.
 
Downloads Adware
After TrojanDownloader:Win32/VB.CQ is downloaded it is run. It attempts to connect to the Web address 'cpa123.cn' and downloads adware.
 
Analysis by Aaron Putnam

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Prevention

Take the following steps to help prevent infection on your system:
  • Enable a firewall on your computer.
  • Get the latest computer updates for all your installed software.
  • Use up-to-date antivirus software.
  • Use caution when opening attachments and accepting file transfers.
  • Use caution when clicking on links to web pages.
  • Protect yourself against social engineering attacks.
Enable a firewall on your computer
Use a third-party firewall product or turn on the Microsoft Windows Internet Connection Firewall.
To turn on the Windows Firewall in Windows Vista
  1. Click Start, and click Control Panel.
  2. Click Security.
  3. Click Turn Windows Firewall on or off.
  4. Select On.
  5. Click OK.
To turn on the Internet Connection Firewall in Windows XP
  1. Click Start, and click Control Panel.
  2. Click Network and Internet Connections. If you do not see Network and Internet Connections, click Switch to Category View.
  3. Click Change Windows Firewall Settings.
  4. Select On.
  5. Click OK.
Get the latest computer updates
Updates help protect your computer from viruses, worms, and other threats as they are discovered. It is important to install updates for all the software that is installed in your computer. These are usually available from vendor websites.
 
You can use the Automatic Updates feature in Windows to automatically download future Microsoft security updates while your computer is on and connected to the Internet.
To turn on Automatic Updates in Windows Vista
  1. Click Start, and click Control Panel. 
  2. Click System and Maintainance.
  3. Click Windows Updates.
  4. Select a setting. Microsoft recommends selecting Install updates automatically and choose a time that is convenient for you. If you do not choose Automatic, but you choose to be notified when updates are ready, a notification balloon appears when new downloads are available to install. Click the notification balloon to review and install the updates.
To turn on Automatic Updates in Windows XP
  1. Click Start, and click Control Panel. 
  2. Click System.
  3. Click Automatic Updates.
  4. Select a setting. Microsoft recommends selecting Automatic. If you do not choose Automatic, but you choose to be notified when updates are ready, a notification balloon appears when new downloads are available to install. Click the notification balloon to review and install the updates.
Use up-to-date antivirus software
Most antivirus software can detect and prevent infection by known malicious software. To help protect you from infection, you should always run antivirus software that is updated with the latest signature files. Antivirus software is available from several sources. For more information, see http://www.microsoft.com/protect/computer/viruses/vista.mspx.
Use caution when opening attachments and accepting file transfers
Exercise caution with e-mail and attachments received from unknown sources, or received unexpectedly from known sources.  Use extreme caution when accepting file transfers from known or unknown sources.
Use caution when clicking on links to web pages
Exercise caution with links to web pages that you receive from unknown sources, especially if the links are to a web page that you are not familiar with or are suspicious of. Malicious software may be installed in your system simply by visiting a web page with harmful content.
Avoid downloading pirated software
Threats may also be bundled with software and files that are available for download on various torrent sites. Downloading "cracked" or "pirated" software from these sites carries not only the risk of being infected with malware, but is also illegal. For more information. please see our article 'The risks of obtaining and using pirated software'.
Protect yourself from social engineering attacks
While attackers may attempt to exploit vulnerabilities in hardware or software in order to compromise a system, they also attempt to exploit vulnerabilities in human behavior in order to do the same. When an attacker attempts to take advantage of human behavior in order to persuade the affected user to perform an action of the attacker's choice, it is known as 'social engineering'. Essentially, social engineering is an attack against the human interface of the targeted system. For more information, please see our article 'What is social engineering?'. 

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Recovery

Microsoft strongly recommends that users apply the update referred to in  Security Bulletin MS08-067 immediately.
 
Manual removal is not recommended for this threat. To detect and remove this threat and other malicious software that may have been installed, run a full-system scan with an up-to-date antivirus product such as the Microsoft online scanner (http://safety.live.com). For more information, see http://www.microsoft.com/protect/computer/viruses/vista.mspx.

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