Cleaning up botnets takes years, if ever, to complete
In late 2008, a worm called Conficker began infecting millions of computers, startling the computer security community into action.
Conficker’s quick spread was so alarming that an organization was formed called the Conficker Working Group that was tasked with stopping the botnet and finding its creators.
Many countries also formed their own groups that worked with Internet service providers to remove infections from users’ computers. But seven years later, there are still about 1 million computers around the world infected with the malware despite the years-long cleanup effort.