Let's face facts. We knew this was coming for years, we just didn't want to admit it to ourselves. Virus programmers—the real kind, not the script kiddies—are far too competent at what they do to have remained noncommercialized forever. No longer merely an ugly toy for troublemakers, the 21st century virus is poised to climb the economic ladder and establish itself as a commercial tool of choice for identity thieves and financial fraudsters.

Engineers at Panda Software, while in the process of researching a new trojan, uncovered evidence this week that led them to a web site touting custom-built viruses for sale. For the low, low price of only US$990, a user gets his or her own pet trojan horse, complete with tech support. If the file is discovered—as this current model was—the designer provides a guarantee to alter it so that it may continue to avoid detection in the face of updated antivirus software.

Call the FTC (Federal Trade Commission) !

Now any executable can contain a new undetected virus?
Only use software that comes with source code that you can compile yourself.

I doubt that most users (myself included) are going to want to compile every single application before they run it.

Just make sure you download from trusted sources.