Symantec has captured an example of what is believed to be the first virus that targets 64-bit Microsoft Windows operating systems.
The company has posted a security advisory for W64.Rugrat.3344 on its web page.
The virus is rated low threat and does not appear to be spreading on the internet. Instead, Symantec believes Rugrat to be a "proof of concept" virus written by the same author of at least six other viruses.
The virus infects Windows Portable Executable files, including many Windows 64 applications, spreading to files in the same folder as the virus file and in subfolders.
Operating systems that support 64-bit processor chips can accommodate longer basic data units, referred to as "words". Older, 32-bit platforms, such as Windows 95, are supported words of up to four bytes, which might contain computer instructions or the address of data stored on the hard drive.
By comparison, 64-bit systems can process eight-byte words and are better suited to processor-intensive demanding tasks, such as graphics rendering.
Rugrat does not appear to be designed to spread, but is a direct-action infector, meaning it stops running immediately after infecting files.
Symantec researchers have linked Rugrat to a family of six viruses called W32.Chiton.gen, which are all believed to be the work of the same author.
Each virus in the family demonstrates a different "first ever" infection technique, including W32.Shrug, the first known virus to use the Thread Local Storage structures in Windows NT, 2000 and XP to run virus code, and W32.Chthon, the first virus to run as a native application in Windows NT, 2000 and XP, Symantec said.