The caution came after an unknown virus writer sent just such an infectious program to UK antivirus company Sophos. Dubbed SWF/LFM-926, the new program does little but infect Flash files on a PC when the movie is played.
"It's really a proof of concept, as opposed to something that you should lie awake at night worrying about," said Graham Cluley, Sophos senior technology consultant. "But whenever a new vulnerability like this is found, other copycats tend to create more malicious variants."
The SWF/LFM-926 should mainly be a concern to Web site designers who use Flash animations to add pizzazz to their sites, Cluley said. Shockwave Flash, created by digital media company Macromedia, is typically used on sites to add interactive user interfaces and multimedia presentations.
Macromedia went even farther, calling the vulnerability through which the virus spread "not that serious".
"Ninety-nine-point-nine percent of the time, people play Flash movies from the Web in their browser," said Pete Santangeli, Macromedia vice president of engineering. "That's completely safe."
It's only when a Flash file or movie is played on a PC through a standalone player included with Macromedia's authoring tools for Web designers that this type of virus can actually infect a PC.
When the infected Flash movie is played, the virus displays the message "Loading.Flash.Movie..." and drops a 926-byte DOS file onto the PC. This file--named V.COM--is run by the virus and infects all other Shockwave Flash files in the current directory. The SWF/LFM-926 virus' name is derived from the abbreviation for Shockwave, the displayed message and the size of the file.
The virus will only infect Windows NT, Windows 2000 and Windows XP systems, but has not yet been seen circulating the Internet. Moreover, since the virus doesn't have a way to spread quickly, it's unlikely to infect a large number of PCs in its current form, said Craig Schmugar, virus research engineer for security-software maker Network Associates.
"It won't be a very affective spreading method if they only use Shockwave Flash," he said, citing NAI tests that confirmed the virus will not spread when the Shockwave Flash is played in a Web browser.
"It is a double-edged sword," he said. "They have given their authoring community an ability to create increased functionality. For the most part, Macromedia has been strict about security; it would have been difficult for them to see this coming."
The virus is not the first to try to fool those PC users with a weakness for Shockwave Flash movies. In December 1999, the ProLin worm spread through e-mail by posing as a Shockwave movie, but in reality it was a simple Windows program file.
SWF/LFM-926 is a pure virus, meaning the program infects files and can only spread when the compromised file is moved to another system.
Macromedia will release a workaround to disable the file association between Shockwave Flash files and the local Flash player within a couple of days, Macromedia's Santangeli said. In addition, the company plans to close the hole in the player by the next version.
For the time being, e-mail users will have to add the SWF file format to their list of attachments of which to be wary.
"Just as we have seen a first Adobe Acrobat file infector and the first AutoCAD file infector, this is just a new way to get into the PC," Sophos' Cluley said. "It does show that the virus writers are always looking for new battlegrounds."
Your article mentions that we need to add .swf files to our list of blocked attachments BUT my reading of the body of the article seems to indicate that the problem lies with the standalone player...
The extension on the standalone player is .exe not .swf, so I wonder if there is really a danger from .swf files or just a continued threat from .exe files??
It would be a great disservice to the web to alarm people about a system which has so much potential (though whose current implementations tend often to be bloated and pointless!). Let's not add fear of viruses to perceptions of this great technology.
Damian