Adware:Adware (or spyware) is a small program that is designed to show advertisements (in various form and degrees of intrusiveness) on your computer. It often reports personal information back to its owners. As a result your sense of privacy can be violated.
SpamTool.Agent.bt is a spyware program that infects computers with the help of spam emails. Also, SpamTool.Agent.bt may be installed through ActiveX exploits and other nefarious avenues. Once it is installed, SpamTool.Agent.bt will secretly send spam emails to all addresses found on the victim machine.
Technical details (How to remove SpamTool.Agent.bt(pop up))