Called W32/Donut, the virus originated in the Czech Republic and targets files running in Microsoft's .net Framework, the set of building blocks that are needed to create and execute XML Web services and other applications in Windows.
Windows XP Professional is Microsoft's first operating system release that includes support for the .net Framework. It is also the central feature of Microsoft's Visual Studio .net developer toolkit. Users who have the .net software running on Windows 2000 or XP could be affected. Anti-virus expert McAfee, however, warned that even users with .net applications only face a low risk of infection.
Unlike most well-known viruses, Donut does not spread itself automatically via e-mail but must be mailed directly to a user or downloaded from a Web site. The program does not damage an infected PC either, it simply infects other .net files with its code and displays a dialog box with the message "This cell has been infected by dotNET virus!" according to Craig Schmugar, a virus researcher at McAfee's Antivirus Emergency Response Team (AVERT) Labs.
The dialog box appears only one in every ten times an infected file is run.
The virus is a proof-of-concept type of program, letting Microsoft know that attackers are awaiting its new set of software and Web services, Schmugar said.
"It does not do a whole lot right now, but we will see a different type of virus down the road because of this," Schmugar said. "This is forward looking, but it lets people know there will be attacks."
The .net Framework includes the Common Language Runtime (CLR) - a developer tool that allows applications to be programmed in various developer languages - as well as class libraries and other programming tools that enable developers to build XML Web services and execute those in Windows.
Two key pieces of the framework, the Common Language Infrastructure (CLI) and Microsoft's programming language C#, were approved as standards in December by European Computer Manufacturers Association (ECMA), a European standards body.
The virus was primarily written in Win32 assembly language and some Microsoft Intermediate Language (MSIL), according to AVERT's Web site. The program attacks other .net executables using the .EXE extension but does not stay resident in memory.