Botnets are particularly insidious, using thousands of virus-infected
computers which their owners are unaware are being used for sending out
spam, launching denial-of-service attacks and stealing data.
But taking down a botnet poses challenges. The main problem is that
legitimate security companies can’t use the same type of weapons as
When the last Kelihos botnet was shut down
in October 2011, for instance, researchers discovered the way the
botnet updated itself. An obvious solution would have been to use this
knowledge to clean thousands of infected machines remotely. But, to do
that without the explicit permission of computer owners would have been
as illegal as the activities of the botnet’s controllers.