Experts tracking a drop in the number of control servers for various ZeuS botnets that are online. Experts say a coordinated takedown effort may have been executed by law enforcement and/or volunteers from the security research community acting in tandem. The number of active servers for the botnet fell instantly from 249 to 181 on the evening of Mar. 9, an expert says. The average of the servers he tracks has anywhere from 20,000 to 50,000 unique infected computers under its thumb.”]
Source: https://krebsonsecurity.com/2010/03/dozens-of-zeus-botnets-knocked-offline/