Grave Danger: Digitally Signed Malwares

Security experts have estimated that more than 200,000 unique malware binaries were discovered in the last couple of years signed with valid digital signatures.

Source: http://resources.infosecinstitute.com/cybercrime-exploits-digital-certificates/

Digital Signature

Below is a definition what is a digital signature:

"Hash value of a message when encrytpted with the private key of a person is his/her digital signature on that document."

As you can deduce from the definition above that the digital signature of a person is different for (almost) every document unlike original signatures. Well maybe you can argue that even two original signatures also cannot be the same. I'll accept it. =)