Abstract
Comprised computer so called bot obey the order of master. These bots perform malicious activities and group together to form botnet. Different mechanism exists to detect the botnet. IP Blacklist is used for this purpose but it also contains some drawbacks. Some legitimate users become the part of IP blacklist because of spoofed IP address. In this paper we have proposed a certified list to remove legitimate users and overcome the deficiency of IP blacklist. We also measure quality of blacklist by determine the responsiveness and completeness of blacklist.