Security researchers have dealt a mighty blow to a spam botnet known as Pushdo, a massive grouping of hacked PCs. Pushdo was responsible for sending more than 10 percent of all junk e-mail worldwide. The botnet has rebounded from similar infrastructure attacks in the past. In January 2010, researchers at Neustar and several ISPs targeted the control servers for the Lethic botnet, another botnet that at the time was estimated to be responsible for relaying roughly one in ten spam e-mails.”]
Source: https://krebsonsecurity.com/2010/08/researchers-kneecap-pushdo-spam-botnet/