24 july, 2010
W32.Changeup.C
Risk Level 2: Low
Discovered: July 23, 2010
Updated: July 23, 2010 10:20:32 AM
Type: Worm
Infection Length: 113,664 bytes
Systems Affected: Windows 98, Windows 95, Windows XP, Windows Me, Windows Vista, Windows NT, Windows Server 2003, Windows 2000
CVE References: CVE-2010-2568
SUMMARY
W32.Changeup.C is a worm that spreads through removable and shared drives and by exploiting the Microsoft Windows Shortcut 'LNK' Files Automatic File Execution Vulnerability (BID 41732).Antivirus Protection Dates
- Initial Rapid Release version July 23, 2010 revision 003
- Latest Rapid Release version July 23, 2010 revision 018
- Initial Daily Certified version pending
- Latest Daily Certified version pending
- Initial Weekly Certified release date July 28, 2010
Threat Assessment
Wild
- Wild Level: Low
- Number of Infections: 0 - 49
- Number of Sites: 0 - 2
- Geographical Distribution: Low
- Threat Containment: Easy
- Removal: Easy
Damage
- Damage Level: Medium
- Payload: Downloads files on to the compromised computer.
Distribution
- Distribution Level: Medium
- Target of Infection: Copies itself to removable and shared drives and uses a remotely exploitable vulnerability.
TECHNICAL DETAILS
When the worm executes, it copies itself to the following location:%UserProfile%\[RANDOM FILE NAME].exe
Next, the worm creates the following registry entry so that it executes whenever Windows starts:
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run\"[RANDOM FILE NAME]" = "%UserProfile%\[RANDOM FILE NAME].exe"
It then modifies the following registry entry in order to hide itself:
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced\"ShowSuperHidden" = "1"
Next, the worm then attempts to download files from the following remote locations, which may be updates of itself:
- [http://]ns3.thepicturehut.net
- [http://]ns4.thepicturehut.net
The worm attempts to spread by copying itself to removable and network shared drives as the following files:
- %DriveLetter%\[RANDOM FILE NAME].exe
- %DriveLetter%\[RANDOM FILE NAME].scr
It also creates the following files on the same drive:
- %DriveLetter%\autorun.inf
- %DriveLetter%\x.exe
- %DriveLetter%\New Folder.lnk
- %DriveLetter%\Passwords.lnk
- %DriveLetter%\Documents.lnk
- %DriveLetter%\Pictures.lnk
- %DriveLetter%\Music.lnk
- %DriveLetter%\Video.lnk
- %DriveLetter%\[RANDOM FILE NAME].dll
- %DriveLetter%\[RANDOM FILE NAME].lnk
The .lnk file uses the Microsoft Windows Shortcut 'LNK' Files Automatic File Execution Vulnerability (BID 41732) to execute [RANDOM FILE NAME].dll.
Recommendations
Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":
- Use a firewall to block all incoming connections from the Internet to services that should not be publicly available. By default, you should deny all incoming connections and only allow services you explicitly want to offer to the outside world.
- 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.
- Ensure that programs and users of the computer use the lowest level of privileges necessary to complete a task. When prompted for a root or UAC password, ensure that the program asking for administration-level access is a legitimate application.
- Disable AutoPlay to prevent the automatic launching of executable files on network and removable drives, and disconnect the drives when not required. If write access is not required, enable read-only mode if the option is available.
- Turn off file sharing if not needed. If file sharing is required, use ACLs and password protection to limit access. Disable anonymous access to shared folders. Grant access only to user accounts with strong passwords to folders that must be shared.
- Turn off and remove unnecessary services. By default, many operating systems install auxiliary services that are not critical. These services are avenues of attack. If they are removed, threats have less avenues of attack.
- If a 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.
- Configure your email server to block or remove email that contains file attachments that are commonly used to spread threats, such as .vbs, .bat, .exe, .pif and .scr files.
- Isolate compromised computers quickly to prevent threats from spreading further. 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.
- If Bluetooth is not required for mobile devices, it should be turned off. If you require its use, ensure that the device's visibility is set to "Hidden" so that it cannot be scanned by other Bluetooth devices. If device pairing must be used, ensure that all devices are set to "Unauthorized", requiring authorization for each connection request. Do not accept applications that are unsigned or sent from unknown sources.
- For further information on the terms used in this document, please refer to the Security Response glossary.