1. What is perpetrator?
ans. Someone who carried out some action, often a bad thing like a crime. A perpetrator is the person who commits the crime; it would be the opposite of a victim.
http://wiki.answers.com/Q/Definition_of_%27perpetrator%27
2. What is cyber-criminal?
ans. When we say cyber-criminal it's generally refers to criminal where a computer or networks is the source, tool, target, or place of a crime. These categories are not exclusive and many activities can be characterized as falling in one or more. Additionally, although the term cyber criminal are more properly restricted to describing criminal activity in which the computer or network is a necessary part of the crime, these terms are also sometimes used to include traditional crimes, such as fraud, theft, blackmail, forgery, and embezzlement, in which computers or networks are used. As the use of computers has grown, computer crime has become more important.
http://en.wikipedia.org/wiki/Cybercrime


3. What is cyber-terrorist?

ans. As the Internet becomes more pervasive in all areas of human endeavor, individuals or groups can use the anonymity afforded by cyberspace to threaten citizens, specific groups (i.e. with membership based on ethnicity or belief), communities and entire countries, without the inherent threat of capture, injury, or death to the attacker that being physically present would bring. When we say cyber-terrorist it is refers to the programmer who breaks into computer systems in order to steal or change or destroy information as a form of cyber-terrorism. And when we say cyber-terrorism it is the leveraging of a target's computers and information , particularly via the Internet, to cause physical, real-world harm or severe disruption of infrastructure.