Worm:Win32/Conficker.A is a worm that infects other computers across a network by exploiting a vulnerability in the Windows Server service (SVCHOST.EXE). If the vulnerability is successfully exploited, it could allow remote code execution when file sharing is enabled.
Microsoft also recommends that users ensure that their network passwords are strong to prevent this worm from spreading via weak administrator passwords. More information is available here.
Microsoft also recommends that users apply an update that changes the AutoPlay functionality in Windows to prevent this worm from spreading via USB drives. More information is available in the Microsoft Knowledgebase Article KB971029.
There are no common symptoms associated with this threat. Alert notifications from installed antivirus software may be the only symptom(s).
Worm:Win32/Conficker.A is a worm that infects other computers across a network by exploiting a vulnerability in the Windows Server service (SVCHOST.EXE). If the vulnerability is successfully exploited, it could allow remote code execution when file sharing is enabled.
Installation
This worm searches for the Windows executable 'services.exe' and will inject itself into it.
This worm copies itself to the Windows system folder as <random>.dll where <random> is a 5-8 character lowercase alphabetic name such as 'nxyme.dll'.
The worm adjusts the file time of the dropped DLL worm copy to the same as the system's kernel32.dll file time to mask forensic evidence of infection time. The registry is modified to execute the dropped DLL worm copy as a service.
Adds value: "DisplayName"
With data: "0"
To subkey: HKLM\SYSTEM\CurrentControlSet\Services\vcdrlxeu
Adds value: "ServiceDll"
With data: "<system folder>\nxyme.dll"
To subkey: HKLM\SYSTEM\ControlSet001\Services\vcdrlxeu\Parameters
Once a machine has been infected the worm will patch the exploited function via a simple code hook in order to prevent re-infecting a machine it has already compromised. The worm opens and listens for connection attempts on a randomly chosen port between 1024 and 10000 and bypasses Windows firewall using APIs. The worm also stops the Internet connection sharing service.
Spreads Via…
Networked Computers
Win32/Conficker.A copies itself into memory and begins propagating to random IP addresses across a network by exploiting a vulnerability in the Windows Server service (SVCHOST.EXE). If the vulnerability is successfully exploited, the worm instructs the target computer to download a copy of the worm from the host computer via HTTP protocol using the random port opened by the worm.
The worm uses the following URLs to determine the computer's geographic location:
getmyip.org
getmyip.co.uk
checkip.dyndns.org
Win32/Conficker.A avoids infecting Ukrainian located computers.
Payload
Creates HTTP Server
The worm opens a random port between 1024 and 10000 and acts like a web server (HTTP server). If the remote machine is exploited successfully, the victim will connect back to the http server and download a worm copy.
Resets System Restore Point
The worm may call an API function to reset the computer's system restore point, potentially defeating recovery using system restore.
Downloads Files
If the date is after November 25, 2008, this worm will build a URL in the following format and attempt to download a file from it:
<random ip?>/search?q=%d&aq=7
If the date is after December 1, 2008 Win32/Conficker.A will attempt to download a file 'loadadv.exe' from the domain 'trafficconverter.biz'.
Additional Information
The name of this threat was derived by selecting fragments of the domain 'trafficconverter.biz', a string found in Worm:Win32/Conficker.A:
(fic)(con)(er) => (con)(fic)(+k)(er) => conficker
Analysis by Joshua Phillips
Take the following steps to help prevent infection on your system:
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Enable a firewall on your computer.
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Use up-to-date antivirus software.
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Use caution when opening attachments and accepting file transfers.
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Use caution when clicking on links to web pages.
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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
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Click Start, and click Control Panel.
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Click Security.
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Click Turn Windows Firewall on or off.
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Select On.
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Click OK.
To turn on the Internet Connection Firewall in Windows XP
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Click Start, and click Control Panel.
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Click Network and Internet Connections. If you do not see Network and Internet Connections, click Switch to Category View.
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Click Change Windows Firewall Settings.
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Select On.
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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
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Click Start, and click Control Panel.
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Click System and Maintainance.
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Click Windows Updates.
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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
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Click Start, and click Control Panel.
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Click System.
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Click Automatic Updates.
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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?'.
Microsoft also recommends that users ensure that their network passwords are strong to prevent this worm from spreading via weak administrator passwords. More information is available
here
.
Microsoft also recommends that users apply an update that changes the AutoPlay functionality in Windows to prevent this worm from spreading via USB drives. More information is available in the
Microsoft Knowledgebase Article KB971029
.
Note: Computers infected by Conficker may be unable to connect to web sites related to security applications and services that may otherwise assist in the removal of this worm (for example, downloading antivirus updates may fail). In this case users will need to use an uninfected computer in order to download any appropriate updates or tools and then transfer these to the infected computer.
Microsoft Help and Support have provided a detailed guide to removing Win32/Conficker infection from an affected computer, either manually or by using the MSRT (Malicious Software Removal Tool).
For detailed instructions on how to manually remove Win32/Conficker, view the following article using an uninfected computer:
Additional information on deploying MSRT in an enterprise environment can be found here:
