- 13 February 2007
- Also Known As:
A New Playground for Virus/Trojan Horse
In 1995, Microsoft Windows 95 arrived. At that time, end of the DOS virus seemed inevitable and a lot of people also thought that DOS batch files were also on the way out.
Although most of the original DOS viruses seem to have disappeared from the wild, viruses such as boot, partition sector and multipartite viruses have continued to thrive happily ignoring the changes around them. After all, these viruses are independent from the operating system as long as they are on an IBM compatible PC.
Meanwhile, the macro virus threat has largely replaced the DOS file virus threats now and is the most commonly reported type of virus today. We are also seeing a rapid growth in viruses that infect Windows executables.
Antivirus Protection Dates
- Initial Rapid Release version 19 December 2000
- Latest Rapid Release version 19 February 2013 revision 016
- Initial Daily Certified version 19 December 2000
- Latest Daily Certified version 09 February 2011 revision 002
- Initial Weekly Certified release date pending
Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.
What a lot of readers did not realize is that the people writing macro viruses have just had a whole new environment for their creations: the Windows Scripting Host (WSH). Yes, this under publicized feature is available as a downloadable module for Windows 95 and Internet Explorer 4, and a standard feature of Windows 98.
Windows Scripting is very similar to DOS batch files and these scripts can run in a DOS prompt using cscript.exe or with in Windows with wscript.exe doing the hosting.
Simply put, the Windows Scripting Host acts as an interpreter between a scripting language that supports the ActiveX Scripting interface such as VB Script, Java Script, and all those wonderful Windows features, including access to folders, file shortcut's, dial-up networking and even the Windows registry.
You may ask, "Is this the next virus threat"? Well it's not the next, it's already here. At the Symantec AntiVirus Research Center (SARC), we have already seen several revisions of a VB Script virus called VBS.Rabbit. This virus simply searches for other script files (*.VBS) in the current directory and overwrites them with the viral code.
VBS.Rabbit.A and VBS.Rabbit.B: These two variants are believed to be "proof of concept" type virus since they're so simple and probably will never spread and become a real threat. The VBS.Rabbit.A variant is very noticeable since it opens a DOS box upon execution. On the 15th of the each month, it creates "The CodeBreakers.URL" with link to the virus author's web site, opens the link, and displays one of the following messages:
VBSv v1.0 by Lord Natas/CodeBreakers
VBSv v1.1 by Lord Natas/CodeBreakers
VBS.Rabbit.C: This is another revision of this VBS overwriter. This one is a little bit more complex than the first two. On the 15th of the month, this one creates "CB.URL" with link to the virus author's web site, opens the link, and displays:
VBSv v2.0 by Lord Natas/CodeBreakers
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.