An anonymous reader writes: Certificates and CAs continue to be a hot topic (think Stuxnet, Duqu, Comodogate, Diginotar, et cetera).
Every now and then we run into malware that has been signed with a code signing certificate. This is problematic, as an unsigned Windows application will produce a warning to the end user if he downloads it from the web — signed applications won't do this. Also some security systems might trust signed code more than unsigned code.
In some of these cases, the certificate has been created by the criminals just for the purpose for signing malware. In other cases they steal code signing certificates (and their passphrases) so they can sign code as someone else.
We recently found a sample signed with a stolen certificate.