The list of antivirus companies that can detect the Storm Worm include Authentium, BitDefender, ClamAV, eSafe, Eset, F-Prot, F-Secure, Kaspersky, McAfee, Sophos, Symantec, Trend Micro, avast! and Windows Live OneCare. The Storm Worm is constantly being updated by its authors to evade antivirus detection, so this does not imply that all the vendors listed above are able to detect all the Storm Worm variants. An intrusion detection system offers some protection from the rootkit, as it may warn that the Windows process "services.exe" is trying to access the Internet using ports 4000 or 7871. Windows 2000, Windows XP and presumably Windows Vista can be infected by all the Storm Worm variants, but Windows Server 2003 cannot, as the malware's author specifically excluded that edition of Windows from the code. Additionally, the decryption layer for some variants requires Windows API functions that are only available in Windows XP Service Pack 2 and later, effectively preventing infection on older versions of Windows.
Peter Gutmann sent an email noting that the Storm botnet comprises between 1 and 10 million PCs depending on whose estimates you believe. Although Dr. Gutmann makes a hardware resource comparison between the Storm botnet and distributed memory and distributed shared memory high performance computers at TOP500, exact performance matches were not his intention—rather a more general appreciation of the botnet's size compared to other massive computing resources. Consider for example the size of the Storm botnet compared to grid computing projects such as the World Community Grid.
An article in PCWorld dated October 21, 2007 says that a network security analyst presented findings at the Toorcon hacker conference in San Diego on October 20, 2007, saying that Storm is down to about 20,000 active hosts or about one-tenth of its former size. However, this is being disputed by security researcher Bruce Schneier, who notes that the network is being partitioned in order to sell the parts off independently.
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