The hackers picked the one day of the year they knew they could inflict the most damage on the world's most valuable company, Saudi Aramco.
On Aug. 15, more than 55,000 Saudi Aramco employees stayed home from work to prepare for one of Islam's holiest nights of the year — Lailat al Qadr, or the Night of Power — celebrating the revelation of the Koran to Muhammad.
That morning, at 11:08, a person with privileged access to the Saudi state-owned oil company's computers, unleashed a computer virus to initiate what is regarded as among the most destructive acts of computer sabotage on a company to date. The virus erased data on three-quarters of Aramco's corporate PCs — documents, spreadsheets, e-mails, files — replacing all of it with an image of a burning American flag.
United States intelligence officials say the attack's real perpetrator was Iran, although they offered no specific evidence to support that claim. But the secretary of defense, Leon E. Panetta, in a recent speech warning of the dangers of computer attacks, cited the Aramco sabotage as "a significant escalation of the cyber threat." In the Aramco case, hackers who called themselves the "Cutting Sword of Justice" and claimed to be activists upset about Saudi policies in the Middle East took responsibility.
But their online message and the burning flag were probably red herrings, say independent computer researchers who have looked at the virus's code.
Immediately after the attack, Aramco was forced to shut down the company's internal corporate network, disabling employees' e-mail and Internet access, to stop the virus from spreading.
It could have been much worse. An examination of the sabotage revealed why government officials and computer experts found the attack disturbing. Aramco's oil production operations are segregated from the company's internal communications network. Once executives were assured that only the internal communications network had been hit and that not a drop of oil had been spilled, they set to work replacing the hard drives of tens of thousands of its PCs and tracking down the parties responsible, according to two people close to the investigation but who were not authorized to speak publicly about it.
Aramco flew in roughly a dozen American computer security experts. By the time those specialists arrived, they already had a good handle on the virus. Within hours of the attack, researchers at Symantec, a Silicon Valley security company, began analyzing a sample of the virus.
That virus — called Shamoon after a word embedded in its code — was designed to do two things: replace the data on hard drives with an image of a burning American flag and report the addresses of infected computers — a bragging list of sorts — back to a computer inside the company's network.
Shamoon's code included a so-called kill switch, a timer set to attack at 11:08 a.m., the exact time that Aramco's computers were wiped of memory. Shamoon's creators even gave the erasing mechanism a name: Wiper.
Computer security researchers noted that the same name, Wiper, had been given to an erasing component of Flame, a computer virus that attacked Iranian oil companies and came to light in May. Iranian oil ministry officials have claimed that the Wiper software code forced them to cut Internet connections to their oil ministry, oil rigs and the Kharg Island oil terminal, a conduit for 80 percent of Iran's oil exports.
It raised suspicions that the Aramco hacking was retaliation. The United States fired one of the first shots in the computer war and has long maintained the upper hand. The New York Times reported in June that the United States, together with Israel, was responsible for Stuxnet, the computer virus used to destroy centrifuges in an Iranian nuclear facility in 2010.
Last May, researchers discovered that Flame had been siphoning data from computers, mainly in Iran, for several years. Security researchers believe Flame and Stuxnet were written by different programmers, but commissioned by the same two nations.
If American officials are correct that Shamoon was designed by Iran, then clues in its code may have been intended to misdirect blame. Shamoon's programmers inserted the word "Arabian Gulf" into its code. But Iranians refer to that body of water as the Persian Gulf and are very protective of the name. (This year, Iran threatened to sue Google for removing the name Persian Gulf from its online maps.)
After analyzing the software code from the Aramco attack, security experts say that the event involved a company insider, or insiders, with privileged access to Aramco's network. The virus could have been carried on a USB memory stick that was inserted into a PC.
Aramco's attackers posted blocks of I.P. addresses of thousands of Aramco PCs online as proof of the attack. Researchers say that only an Aramco employee or contractor with access to the company's internal network would have been able to grab that list from a disconnected computer inside Aramco's network and put it online.
Neither researchers nor officials have disclosed the names of the attackers involved. Saudi Aramco said in a statement that it was inappropriate to comment amid an investigation. The company further stated that it does not comment on rumor or speculation.
American intelligence officials blame Iran for a similar, subsequent attack on RasGas, the Qatari natural gas giant, two weeks after the Aramco attack. They also believe Iran engineered computer attacks that intermittently took America's largest banks offline in September, and last week disrupted the online banking Web sites of Capital One and BB&T.
Multiple requests for comment from Iran's interests office in Washington and to Iran's mission to the United Nations in New York brought no response.
The finger-pointing demonstrates the growing concern in the United States among government officials and private industry that other countries have the technology and skill to initiate attacks. "The Iranians were faster in developing an attack capability and bolder in using it than we had expected," said James A. Lewis, a former diplomat and cybersecurity expert at the Center for Strategic and International Studies. "Both sides are going through a dance to figure out how much they want to turn this into a fight."
More than two months after the Aramco attack, the company continues to deal with the aftermath. Still, this month employees were not able to gain access to their corporate e-mail and internal network for several days. Until the company's executives decide its systems are secure, employees can no longer access Aramco's internal network remotely.
The attack, intelligence officials say, was a wake-up call. "It proved you don't have to be sophisticated to do a lot of damage," said Richard A. Clarke, the former counterterrorism official at the National Security Council. "There are lots of targets in the U.S. where they could do the same thing. The attacks were intended to say: 'If you mess with us, you can expect retaliation.' "