This is a powerful virus making tool, coded in Visual Basic. By this tool you can create your own virus, it is very easy to use.

The most important thing is that it makes a real virus so obviously your antivirus software will detect it as a Virus or Trojan or Worm.
But the virus making tool is not harmfull, the only harmfull thing is that what the tool creates or generates i.e. a virus.
Do not execute the Virus (made by Terabit Virus Maker) in your PC. So please handle it very very carefully...