The amount of unique Zeus botnets is likely to be in the hundreds. The cyber criminals behind the Zeus botnet will sell it to anyone who can start their own unique botnet. There are some side-branches of Zeus maintained by other cyber criminals. The security community is reasonably sure that a certain bot is controlled by one cyber criminal group we can refer to the threat as a botnet. Examples of this rule are Conficker, Storm and Mebroot. If the bot is available in the underground we should refer to it as bot or botnets created by the following bot. Examples are Zeus, SpyEye and Poison Ivy.”]
Source: https://securelist.com/will-the-real-zeus-botnet-please-stand-up/29692/