From The New York Times‘ “An Army of Soulless 1’s and 0’s“:
Officials at the F.B.I. and the Justice Department say their inquiries on the zombie networks are exposing serious vulnerabilities in the Internet that could be exploited more widely by saboteurs to bring down Web sites or online messaging systems. One case under investigation, officials say, may involve as many as 300,000 zombie computers …
In one recent case, a small British online payment processing company, Protx, was shut down after being bombarded in a zombie attack and warned that problems would continue unless a $10,000 payment was made, the company said. It is not known whether the authorities ever arrested anyone in that case. …
More than 170,000 computers every day are being added to the ranks of zombies, according to Dmitri Alperovitch, a research engineer at CipherTrust, a company based in Georgia that sells products to make e-mail and messaging safer. …
Mr. Alperovitch said that CipherTrust had detected a sharp rise in zombie computers in recent months, from a daily average of 143,000 newly commandeered computers in March to 157,000 in April to 172,000 last month.
He said that the increase was attributable to two trends: the rising number of computers in Asia, particularly China, which do not use software to protect against zombies and the worldwide proliferation of high-speed Internet connections.