Stuxnet

Stuxnet attacked Windows systems using an unprecedented four zero-day attacks (plus the CPLINK vulnerability and a vulnerability used by the Conficker worm[51]). It is initially spread using infected removable drives such as USB flash drives,[21][45] which contain Windows shortcut files to initiate executable code.[52] The worm then uses other exploits and techniques such as peer-to-peer remote procedure call (RPC) to infect and update other computers inside private networks that are not directly connected to the Internet.[53][54][55] The number of zero-day exploits used is unusual, as they are highly valued and malware creators do not typically make use of (and thus simultaneously make visible) four different zero-day exploits in the same worm.[23] Amongst these exploits were remote code execution on a computer with Printer Sharing enabled,[56] and the LNK/PIF vulnerability,[57] in which file execution is accomplished when an icon is viewed in Windows Explorer, negating the need for user interaction.[58] Stuxnet is unusually large at half a megabyte in size,[53] and written in several different programming languages (including C and C++) which is also irregular for malware.[15][20][50] The Windows component of the malware is promiscuous in that it spreads relatively quickly and indiscriminately.[45]

The malware has both user mode and kernel mode rootkit ability under Windows,[55] and its device drivers have been digitally signed with the private keys of two public key certificates that were stolen from separate well-known companies, JMicron and Realtek, both located at Hsinchu Science Park in Taiwan.[45][53] The driver signing helped it install kernel mode rootkit drivers successfully without users being notified, and thus it remained undetected for a relatively long period of time.[59] Both compromised certificates have been revoked by Verisign.

Two websites in Denmark and Malaysia were configured as command and control servers for the malware, allowing it to be updated, and for industrial espionage to be conducted by uploading information. Both of these domain names have subsequently been redirected by their DNS service provider to Dynadot as part of a global effort to disable the malware.[55][38]

Overview of normal communications between Step 7 and a Siemens PLC

Overview of Stuxnet hijacking communication between Step 7 software and a Siemens PLC

According to researcher Ralph Langner,[60][61] once installed on a Windows system Stuxnet infects project files belonging to Siemens' WinCC/PCS 7 SCADA control software[62] (Step 7), and subverts a key communication library of WinCC called s7otbxdx.dll. Doing so intercepts communications between the WinCC software running under Windows and the target Siemens PLC devices that the software is able to configure and program when the two are connected via a data cable. In this way, the malware is able to install itself on PLC devices unnoticed, and subsequently to mask its presence from WinCC if the control software attempts to read an infected block of memory from the PLC system.[55]

The malware furthermore used a zero-day exploit in the WinCC/SCADA database software in the form of a hard-coded database password.[63]

Siemens Simatic S7-300 PLC CPU with three I/O modules attached

The entirety of the Stuxnet code has not yet been disclosed, but its payload targets only those SCADA configurations that meet criteria that it is programmed to identify.[38]

Stuxnet requires specific slave variable-frequency drives (frequency converter drives) to be attached to the targeted Siemens S7-300 system and its associated modules. It only attacks those PLC systems with variable-frequency drives from two specific vendors: Vacon based in Finland and Fararo Paya based in Iran.[64] Furthermore, it monitors the frequency of the attached motors, and only attacks systems that spin between 807 Hz and 1,210 Hz. The industrial applications of motors with these parameters are diverse, and may include pumps or gas centrifuges.

Stuxnet installs malware into memory block DB890 of the PLC that monitors the Profibus messaging bus of the system.[55] When certain criteria are met, it periodically modifies the frequency to 1,410 Hz and then to 2 Hz and then to 1,064 Hz, and thus affects the operation of the connected motors by changing their rotational speed.[64] It also installs a rootkit – the first such documented case on this platform – that hides the malware on the system and masks the changes in rotational speed from monitoring systems.

Ralph Langner, the researcher who identified that Stuxnet infected PLCs,[21] first speculated publicly in September 2010 that the malware was of Israeli origin, and that it targeted Iranian nuclear facilities.[82] However Langner more recently, at a TED conference, recorded in February 2011, stated that, "My opinion is that the Mossad is involved, but that the leading force is not Israel. The leading force behind Stuxnet is the cyber superpower – there is only one; and that's the United States."[83] Kevin Hogan, Senior Director of Security Response at Symantec, reported that most infected systems were in Iran (about 60%),[84] which has led to speculation that it may have been deliberately targeting "high-value infrastructure" in Iran[23] including either the Bushehr Nuclear Power Plant or the Natanz nuclear facility.[53][85][86] Langner called the malware "a one-shot weapon" and said that the intended target was probably hit,[87] although he admitted this was speculation.[53] Another German researcher and spokesman of the German-based Chaos Computer Club, Frank Rieger, was the first to speculate that Natanz was the target.[38]

Anti-aircraft guns guarding Natanz Nuclear Facility

External image

Satellite Imagery of the Natanz Enrichment Facility[88]

According to the Israeli newspaper Haaretz, in September 2010 experts on Iran and computer security specialists were increasingly convinced that Stuxnet was meant "to sabotage the uranium enrichment facility at Natanz – where the centrifuge operational capacity had dropped over the past year by 30 percent."[89] On 23 November 2010 it was announced that uranium enrichment at Natanz had ceased several times because of a series of major technical problems.[90][91] A "serious nuclear accident" (supposedly the shutdown of some of its centrifuges[92]) occurred at the site in the first half of 2009, which is speculated to have forced Gholam Reza Aghazadeh, the head of the Atomic Energy Organization of Iran (AEOI) to resign.[93] Statistics published by the Federation of American Scientists (FAS) show that the number of enrichment centrifuges operational in Iran mysteriously declined from about 4,700 to about 3,900 beginning around the time the nuclear incident WikiLeaks mentioned would have occurred.[94] The Institute for Science and International Security (ISIS) suggests, in a report published in December 2010, that Stuxnet is a reasonable explanation for the apparent damage[95] at Natanz, and may have destroyed up to 1,000 centrifuges (10 percent) sometime between November 2009 and late January 2010. The authors conclude:

The attacks seem designed to force a change in the centrifuge’s rotor speed, first raising the speed and then lowering it, likely with the intention of inducing excessive vibrations or distortions that would destroy the centrifuge. If its goal was to quickly destroy all the centrifuges in the FEP [Fuel Enrichment Plant], Stuxnet failed. But if the goal was to destroy a more limited number of centrifuges and set back Iran’s progress in operating the FEP, while making detection difficult, it may have succeeded, at least temporarily.[95]

The ISIS report further notes that Iranian authorities have attempted to conceal the breakdown by installing new centrifuges on a large scale.[95][96]

The worm worked by first causing an infected Iranian IR-1 centrifuge to increase from its normal operating speed of 1,064 hertz to 1,410 hertz for 15 minutes before returning to its normal frequency. Twenty-seven days later, the worm went back into action, slowing the infected centrifuges down to a few hundred hertz for a full 50 minutes. The stresses from the excessive, then slower, speeds caused the aluminium centrifugal tubes to expand, often forcing parts of the centrifuges into sufficient contact with each other to destroy the machine.[97]

According to The Washington Post, International Atomic Energy Agency (IAEA) cameras installed in the Natanz facility recorded the sudden dismantling and removal of approximately 900–1,000 centrifuges during the time the Stuxnet worm was reportedly active at the plant. Iranian technicians, however, were able to quickly replace the centrifuges and the report concluded that uranium enrichment was likely only briefly disrupted.[98]

On 15 February 2011, the Institute for Science and International Security released a report concluding that:

Assuming Iran exercises caution, Stuxnet is unlikely to destroy more centrifuges at the Natanz plant. Iran likely cleaned the malware from its control systems. To prevent re-infection, Iran will have to exercise special caution since so many computers in Iran contain Stuxnet. Although Stuxnet appears to be designed to destroy centrifuges at the Natanz facility, destruction was by no means total. Moreover, Stuxnet did not lower the production of low enriched uranium (LEU) during 2010. LEU quantities could have certainly been greater, and Stuxnet could be an important part of the reason why they did not increase significantly. Nonetheless, there remain important questions about why Stuxnet destroyed only 1,000 centrifuges. One observation is that it may be harder to destroy centrifuges by use of cyber attacks than often believed.[99]

The Associated Press reported that the semi-official Iranian Students News Agency released a statement on 24 September 2010 stating that experts from the Atomic Energy Organization of Iran met in the previous week to discuss how Stuxnet could be removed from their systems.[19] According to analysts, such as David Albright, Western intelligence agencies had been attempting to sabotage the Iranian nuclear program for some time.[100][101]

The head of the Bushehr Nuclear Power Plant told Reuters that only the personal computers of staff at the plant had been infected by Stuxnet and the state-run newspaper Iran Daily quoted Reza Taghipour, Iran's telecommunications minister, as saying that it had not caused "serious damage to government systems".[79] The Director of Information Technology Council at the Iranian Ministry of Industries and Mines, Mahmud Liaii, has said that: "An electronic war has been launched against Iran... This computer worm is designed to transfer data about production lines from our industrial plants to locations outside Iran."[102]

In response to the infection, Iran assembled a team to combat it. With more than 30,000 IP addresses affected in Iran, an official said that the infection was fast spreading in Iran and the problem had been compounded by the ability of Stuxnet to mutate. Iran had set up its own systems to clean up infections and had advised against using the Siemens SCADA antivirus since it is suspected that the antivirus contains embedded codes which update Stuxnet instead of remove it.[103][104][105][106]

According to Hamid Alipour, deputy head of Iran's government Information Technology Company, "The attack is still ongoing and new versions of this virus are spreading." He reported that his company had begun the cleanup process at Iran's "sensitive centres and organizations."[104] "We had anticipated that we could root out the virus within one to two months, but the virus is not stable, and since we started the cleanup process three new versions of it have been spreading", he told the Islamic Republic News Agency on 27 September 2010.[106]

On 29 November 2010, Iranian president Mahmoud Ahmadinejad stated for the first time that a computer virus had caused problems with the controller handling the centrifuges at its Natanz facilities. According to Reuters, he told reporters at a news conference in Tehran, "They succeeded in creating problems for a limited number of our centrifuges with the software they had installed in electronic parts."[107][108]

On the same day two Iranian nuclear scientists were targeted in separate, but nearly simultaneous car bomb attacks near Shahid Beheshti University in Tehran. Majid Shahriari, a quantum physicist was killed. Fereydoon Abbasi, a high-ranking official at the Ministry of Defense was seriously wounded. Wired speculated that the assassinations could indicate that whoever was behind Stuxnet felt that it was not sufficient to stop the nuclear program.[109] That same Wired article suggested the Iranian government could have been behind the assassinations.[109] In January 2010, another Iranian nuclear scientist, a physics professor at Tehran University, was killed in a similar bomb explosion.[109] On 11 January 2012, a Director of the Natanz nuclear enrichment facility, Mostafa Ahmadi Roshan, was killed in an attack quite similar to the one that killed Shahriari.[110]

An analysis by the FAS demonstrates that Iran's enrichment capacity grew during 2010. The study indicated that Iran's centrifuges appeared to be performing 60% better than in the previous year, which would significantly reduce Tehran's time to produce bomb-grade uranium. The FAS report was reviewed by an official with the IAEA who affirmed the study.[111][112][113]

European and US officials, along with private experts told Reuters that Iranian engineers were successful in neutralizing and purging Stuxnet from their country's nuclear machinery.[114]

Given the growth in Iranian enrichment ability in 2010, the country may have intentionally put out misinformation to cause Stuxnet's creators to believe that the worm was more successful in disabling the Iranian nuclear program than it actually was.[38]

Israel, through Unit 8200,[115][116] has been speculated to be the country behind Stuxnet in many media reports[78][92][117] and by experts such as Richard A. Falkenrath, former Senior Director for Policy and Plans within the US Office of Homeland Security.[118][79] Yossi Melman, who covers intelligence for Israeli newspaper Haaretz and wrote a book about Israeli intelligence, also suspected that Israel was involved, noting that Meir Dagan, the former (up until 2011) head of the national intelligence agency Mossad, had his term extended in 2009 because he was said to be involved in important projects. Additionally, in 2010 Israel grew to expect that Iran would have a nuclear weapon in 2014 or 2015 – at least three years later than earlier estimates – without the need for an Israeli military attack on Iranian nuclear facilities; "They seem to know something, that they have more time than originally thought", he added.[28][49] Israel has not publicly commented on the Stuxnet attack but in 2010 confirmed that cyberwarfare was now among the pillars of its defense doctrine, with a military intelligence unit set up to pursue both defensive and offensive options.[119][120][121] When questioned whether Israel was behind the virus in the fall of 2010, some Israeli officials broke into "wide smiles", fueling speculation that the government of Israel was involved with its genesis.[122] American presidential advisor Gary Samore also smiled when Stuxnet was mentioned,[49] although American officials have suggested that the virus originated abroad.[122] According to The Telegraph, Israeli newspaper Haaretz reported that a video celebrating operational successes of Gabi Ashkenazi, retiring Israel Defense Forces (IDF) Chief of Staff, was shown at his retirement party and included references to Stuxnet, thus strengthening claims that Israel's security forces were responsible.[123]

In 2009, a year before Stuxnet was discovered, Scott Borg of the United States Cyber-Consequences Unit (US-CCU)[124] suggested that Israel may prefer to mount a cyber-attack rather than a military strike on Iran's nuclear facilities.[101] And, in late 2010 Borg stated, "Israel certainly has the ability to create Stuxnet and there is little downside to such an attack because it would be virtually impossible to prove who did it. So a tool like Stuxnet is Israel's obvious weapon of choice."[125] Iran uses P-1 centrifuges at Natanz, the design for which A. Q. Khan stole in 1976 and took to Pakistan. His black market nuclear-proliferation network sold P-1s to, among other customers, Iran. Experts believe that Israel also somehow acquired P-1s and tested Stuxnet on the centrifuges, installed at the Dimona facility that is part of its own nuclear program.[49] The equipment may be from the United States, which received P-1s from Libya's former nuclear program.[126][49]

Some have also cited several clues in the code such as a concealed reference to the word MYRTUS, believed to refer to the Myrtle tree, or Hadassah in Hebrew. Hadassah was the birth name of the former Jewish queen of Persia, Queen Esther.[127][128] However, it may be that the "MYRTUS" reference is simply a misinterpreted reference to SCADA components known as RTUs (Remote Terminal Units) and that this reference is actually "My RTUs"–a management feature of SCADA.[129] Also, the number 19790509 appears once in the code and may refer to the date 1979 May 09, the day Habib Elghanian, a Persian Jew, was executed in Tehran.[55][130][131] Another date that appears in the code is "24 September 2007", the day that Iran's president Mahmoud Ahmadinejad spoke at Columbia University and made comments questioning the validity of the Holocaust.[38] Such data is not conclusive, since, as noted by Symantec, "...attackers would have the natural desire to implicate another party".[55]

There has also been testimony on the involvement of the United States and its collaboration with Israel,[132][133] with one report stating that "there is vanishingly little doubt that [it] played a role in creating the worm."[38] It has been reported that the United States, under one of its most secret programs, initiated by the Bush administration and accelerated by the Obama administration,[134] has sought to destroy Iran's nuclear program by novel methods such as undermining Iranian computer systems. A diplomatic cable obtained by WikiLeaks showed how the United States was advised to target Iran's nuclear abilities through 'covert sabotage'.[135] A New York Times article as early as January 2009 credited a then unspecified program with preventing an Israeli military attack on Iran where some of the efforts focused on ways to destabilize the centrifuges.[136] A Wired article claimed that Stuxnet "is believed to have been created by the United States".[137]

The fact that John Bumgarner, a former intelligence officer and member of the United States Cyber-Consequences Unit (US-CCU), published an article prior to Stuxnet being discovered or deciphered, that outlined a strategic cyber strike on centrifuges[138] and suggests that cyber attacks are permissible against nation states which are operating uranium enrichment programs that violate international treaties gives some credibility to these claims. Bumgarner pointed out that the centrifuges used to process fuel for nuclear weapons are a key target for cybertage operations and that they can be made to destroy themselves by manipulating their rotational speeds.[139]

In a March 2012 interview with 60 Minutes, retired US Air Force General Michael Hayden – who served as director of both the Central Intelligence Agency and National Security Agency – while denying knowledge of who created Stuxnet said that he believed it had been "a good idea" but that it carried a downside in that it had legitimized the use of sophisticated cyber weapons designed to cause physical damage. Hayden said, "There are those out there who can take a look at this... and maybe even attempt to turn it to their own purposes". In the same report, Sean McGurk, a former cybersecurity official at the Department of Homeland Security noted that the Stuxnet source code could now be downloaded online and modified to be directed at new target systems. Speaking of the Stuxnet creators, he said, "They opened the box. They demonstrated the capability... It's not something that can be put back."[140]

In April 2011 Iranian government official Gholam Reza Jalali stated that an investigation had concluded that the United States and Israel were behind the Stuxnet attack.[141] Frank Rieger stated that three European countries' intelligence agencies agreed that Stuxnet was a joint United States-Israel effort. The code for the Windows injector and the PLC payload differ in style, likely implying collaboration. Other experts believe that a US-Israel cooperation is unlikely because "the level of trust between the two countries' intelligence and military establishments is not high."[38]

A Wired magazine article about US General Keith B. Alexander stated: "And he and his cyber warriors have already launched their first attack. The cyber weapon that came to be known as Stuxnet was created and built by the NSA in partnership with the CIA and Israeli intelligence in the mid-2000s."[142]

China,[143] Jordan, and France are other possibilities, and Siemens may have also participated.[38][132] Langner speculated that the infection may have spread from USB drives belonging to Russian contractors since the Iranian targets were not accessible via the Internet.[21][144] In 2019 it was reported that an Iranian mole working for the Dutch intelligence at the behest of Israel and the CIA inserted the Stuxnet virus with a USB flash drive or convinced another person working at the Natanz facility to do so.[145][146]

Sandro Gaycken from the Free University Berlin argued that the attack on Iran was a ruse to distract from Stuxnet's real purpose. According to him, its broad dissemination in more than 100,000 industrial plants worldwide suggests a field test of a cyber weapon in different security cultures, testing their preparedness, resilience, and reactions, all highly valuable information for a cyberwar unit.[147]

The United Kingdom has denied involvement in the worm's creation.[148]

Stratfor Documents released by WikiLeaks suggest that the International Security Firm 'Stratfor' believe that Israel is behind Stuxnet – "But we can't assume that because they did Stuxnet that they are capable of doing this blast as well".[149]

In July 2013, Edward Snowden claimed that Stuxnet was cooperatively developed by the United States and Israel.[150]

According to a report by Reuters, the NSA also tried to sabotage North Korea's nuclear program using a version of Stuxnet. The operation was reportedly launched in tandem with the attack that targeted Iranian centrifuges in 2009–10. The North Korean nuclear program shares many similarities with the Iranian, both having been developed with technology transferred by Pakistani nuclear scientist A.Q. Khan. The effort failed, however, because North Korea's extreme secrecy and isolation made it impossible to introduce Stuxnet into the nuclear facility.[151]

Gholamreza Jalali, Iran's chief of the National Passive Defence Organisation (NPDO), claims that his country fended off a Stuxnet-like attack targeting the country's telecom infrastructure. Iran's Telecommunications minister Mohammad-Javad Azari Jahromi has since accused Israel of orchestrating the attack. Iran plans to sue Israel through International Court of Justice (ICJ) and is also willing to launch a retaliation attack if Israel does not desist.[152]

A November 2013 article[153] in Foreign Policy magazine claims existence of an earlier, much more sophisticated attack on the centrifuge complex at Natanz, focused on increasing centrifuge failure rate over a long time period by stealthily inducing uranium hexafluoride gas overpressure incidents. This malware was capable of spreading only by being physically installed, probably by previously contaminated field equipment used by contractors working on Siemens control systems within the complex. It is not clear whether this attack attempt was successful, but it being followed by a different, simpler and more conventional attack is indicative.

On 1 September 2011, a new worm was found, thought to be related to Stuxnet. The Laboratory of Cryptography and System Security (CrySyS) of the Budapest University of Technology and Economics analyzed the malware, naming the threat Duqu.[154][155] Symantec, based on this report, continued the analysis of the threat, calling it "nearly identical to Stuxnet, but with a completely different purpose", and published a detailed technical paper.[156] The main component used in Duqu is designed to capture information[50] such as keystrokes and system information. The exfiltrated data may be used to enable a future Stuxnet-like attack. On 28 December 2011, Kaspersky Lab's director of global research and analysis spoke to Reuters about recent research results showing that the platform Stuxnet and Duqu both originated in 2007, and is being referred to as Tilded due to the ~d at the beginning of the file names. Also uncovered in this research was the possibility for three more variants based on the Tilded platform.[157]

In May 2012, the new malware "Flame" was found, thought to be related to Stuxnet.[158] Researchers named the program "Flame" after the name of one of its modules.[158] After analysing the code of Flame, Kaspersky Lab said that there is a strong relationship between Flame and Stuxnet. An early version of Stuxnet contained code to propagate infections via USB drives that is nearly identical to a Flame module that exploits the same vulnerability.[159]

In December 2017 it was reported that the safety systems of an unidentified power station, believed to be in Saudi Arabia, were compromised, when the Triconex industrial safety technology made by Schneider Electric SE was targeted, in what is believed to have been a state sponsored attack. The computer security company Symantec claimed that the malware, known as "Triton", exploited a vulnerability in computers running the Microsoft Windows operating system.[160]