The Storm botnet or Storm worm botnet is a remotely-controlled network of “zombie” computers (or “botnet”) that has been linked by the Storm Worm, a Trojan horse spread through e-mail spam. Some have estimated that by September 2007 the Storm botnet was running on anywhere from 1 million to 50 million computer systems. Other sources have placed the size of the botnet to be around 250,000 to 1 million compromised systems. More conservatively, one network security analyst claims to have developed software that has crawled the botnet and estimates that it controls 160,000 infected computers. The Storm botnet was first identified around January 2007, with the Storm worm at one point accounting for 8% of all malware on Microsoft Windows computers.
The Storm botnet has been used in a variety of criminal activities. Its controllers, and the authors of the Storm Worm, have not yet been identified. The Storm botnet has displayed defensive behaviors that indicated that its controllers were actively protecting the botnet against attempts at tracking and disabling it. The botnet has specifically attacked the online operations of some security vendors and researchers who attempted to investigate the botnet. Security expert Joe Stewart revealed that in late 2007, the operators of the botnet began to further decentralize their operations, in possible plans to sell portions of the Storm botnet to other operators. Some reports as of late 2007 indicated the Storm botnet to be in decline, but many security experts reported that they expect the botnet to remain a major security risk online, and the United States Federal Bureau of Investigation considers the botnet a major risk to increased bank fraud, identity theft, and other cybercrimes.
The botnet reportedly is powerful enough as of September 2007 to force entire countries off the Internet, and is estimated to be capable of executing more instructions per second than some of the world’s top supercomputers. However, it is not a completely accurate comparison, according to security analyst James Turner, who said that comparing a botnet to a supercomputer is like comparing an army of snipers to a nuclear weapon. Bradley Anstis, of the United Kingdom security firm Marshal, said, “The more worrying thing is bandwidth. Just calculate four million times a standard ADSL connection. That’s a lot of bandwidth. It’s quite worrying. Having resources like that at their disposal—distributed around the world with a high presence and in a lot of countries—means they can deliver very effective distributed attacks against hosts.”
First detected on the Internet in January 2007, the Storm botnet and worm are so-called because of the storm-related subject lines its infectious e-mail employed initially, such as “230 dead as storm batters Europe.” Later provocative subjects included, “Chinese missile shot down USA aircraft,” and “U.S. Secretary of State Condoleezza Rice has kicked German Chancellor Angela Merkel.” It is suspected by some information security professionals that well-known fugitive spammers, including Leo Kuvayev, may be involved in the operation and control of the Storm botnet. According to technology journalist Daniel Tynan, writing under his “Robert X. Cringely” pseudonym, a great portion of the fault for the existence of the Storm botnet lay with Microsoft and Adobe Systems. Other sources state that Storm Worm’s primary method of victim acquisition is through enticing users via frequently changing social engineering schemes. According to Patrick Runald, the Storm botnet has a strong American focus, and likely has agents working to support it within the United States. Some experts, however, believe the Storm botnet controllers are Russian, some pointing specifically at the Russian Business Network, citing that the Storm software mentions a hatred of the Moscow-based security firm Kaspersky Lab, and includes the Russian word “buldozhka,” which means “bulldog.
The botnet, or zombie network, comprises computers running Microsoft Windows as their operating system. Once infected, a computer becomes known as a bot. This bot then performs automated tasks—anything from gathering data on the user, to attacking web sites, to forwarding infected e-mail—without its owner’s knowledge or permission. Estimates indicate that 5,000 to 6,000 computers are dedicated to propagating the spread of the worm through the use of e-mails with infected attachments; 1.2 billion virus messages have been sent by the botnet through September 2007, including a record 57 million on August 22, 2007 alone. Lawrence Baldwin, a computer forensics specialist, was quoted as saying, “Cumulatively, Storm is sending billions of messages a day. It could be double digits in the billions, easily.” One of the methods used to entice victims to infection-hosting web sites are offers of free music, for artists such as Beyoncé Knowles, Kelly Clarkson, Rihanna, The Eagles, Foo Fighters, R. Kelly, and Velvet Revolver. Signature-based detection, the main defense of most computer systems against virus and malware infections, is hampered by the large number of Storm variants.
Back-end servers that control the spread of the botnet and Storm worm automatically re-encode their distributed infection software twice an hour, for new transmissions, making it difficult for anti-virus vendors to stop the virus and infection spread. Additionally, the location of the remote servers which control the botnet are hidden behind a constantly changing DNS technique called ‘fast flux’, making it difficult to find and stop virus hosting sites and mail servers. In short, the name and location of such machines are frequently changed and rotated, often on a minute by minute basis. The Storm botnet’s operators control the system via peer-to-peer techniques, making external monitoring and disabling of the system more difficult. There is no central “command-and-control point” in the Storm botnet that can be shut down. The botnet also makes use of encrypted traffic. Efforts to infect computers usually revolve around convincing people to download e-mail attachments which contain the virus through subtle manipulation. In one instance, the botnet’s controllers took advantage of the National Football League’s opening weekend, sending out mail offering “football tracking programs” which did nothing more than infect a user’s computer. According to Matt Sergeant, chief anti-spam technologist at MessageLabs, “In terms of power, [the botnet] utterly blows the supercomputers away. If you add up all 500 of the top supercomputers, it blows them all away with just 2 million of its machines. It’s very frightening that criminals have access to that much computing power, but there’s not much we can do about it.” It is estimated that only 10%-20% of the total capacity and power of the Storm botnet is currently being used.
Computer security expert Joe Stewart detailed the process by which compromised machines join the botnet: attempts to join the botnet are made by launching a series of EXE files on the computer system in question, in stages. Usually, they are named in a sequence from game0.exe through game5.exe, or similar. It will then continue launching executables in turn. They typically perform the following:
1. game0.exe – Backdoor/downloader
2. game1.exe – SMTP relay
3. game2.exe – E-mail address stealer
4. game3.exe – E-mail virus spreader
5. game4.exe – Distributed denial of service (DDos) attack tool
6. game5.exe – Updated copy of Storm Worm dropper
At each stage the compromised system will connect into the botnet; fast flux DNS makes tracking this process exceptionally difficult. This code is run from %windir%system32wincom32.sys on a Windows system, via a kernel rootkit, and all connections back to the botnet are sent through a modified version of the eDonkey/Overnet communications protocol.
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