The Storm botnet or Storm worm botnet (not to be confused with StormBot, which is a TCL script that is not malicious) 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.
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 is reportedly 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.
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.
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.
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:
- game0.exe - Backdoor/downloader
- game1.exe - SMTP relay
- game2.exe - E-mail address stealer
- game3.exe - E-mail virus spreader
- game4.exe - Distributed denial of service (DDoS) attack tool
- 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%\system32\wincom32.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.
The Storm botnet's systems also take steps to defend itself locally, on victims' computer systems. The botnet, on some compromised systems, creates a computer process on the Windows machine that notifies the Storm systems whenever a new program or other processes begin. Previously, the Storm worms locally would tell the other programs — such as anti-virus, or anti-malware software, to simply not run. However, according to IBM security research, versions of Storm also now simply "fool" the local computer system to run the hostile program successfully, but in fact, they are not doing anything. "Programs, including not just AV exes, dlls and sys files, but also software such as the P2P applications BearShare and eDonkey, will appear to run successfully, even though they didn't actually do anything, which is far less suspicious than a process that gets terminated suddenly from the outside.
On September 25, 2007, it was estimated that a Microsoft update to the Windows Malicious Software Removal Tool (MSRT) may have helped reduce the size of the botnet by up to 20%. The new patch, as claimed by Microsoft, removed Storm from approximately 274,372 infected systems out of 2.6 million scanned Windows systems. However, according to senior security staff at Microsoft, "the 180,000+ additional machines that have been cleaned by MSRT since the first day are likely to be home user machines that were not notably incorporated into the daily operation of the 'Storm' botnet," indicating that the MSRT cleaning may have been symbolic at best.
The computer security company McAfee is reported as saying that the Storm Worm would be the basis of future attacks. Craig Schmugar, a noted security expert who discovered the Mydoom worm, called the Storm botnet a trend-setter, which has led to more usage of similar tactics by criminals. One such derivative botnet has been dubbed the "Celebrity Spam Gang", due to their use of similar technical tools as the Storm botnet controllers. Unlike the sophisticated social engineering that the Storm operators use to entice victims, however, the Celebrity spammers make use of offers of nude images of celebrities such as Angelina Jolie and Britney Spears.
Cisco Systems security experts stated in a report that they believe the Storm botnet would remain a critical threat in 2008, and said they estimated that its size remained in the "millions".
The Storm botnet was sending out spam for more than two years until its decline in late 2008. One factor in this, on account of making it less interesting for the creators to maintain the botnet, may have been the Stormfucker tool, which made it possible to take control over parts of the botnet.
On April 28, 2010, McAfee made an announcement that the so-called "rumors" of a Stormbot 2 were verified. Mark Schloesser, Tillmann Werner, and Felix Leder, the German researchers who did a lot of work in analyzing the original Storm, found that around two-thirds of the “new” functions are a copy and paste from the last Storm code base. The only thing missing is the P2P infrastructure, perhaps because of the tool which used P2P to bring down the original Storm. Honeynet blog dubbed this Stormbot 2.