Within hours after a virus had devastated the computer network of Saudi Arabian Oil Co., the world’s largest state-owned crude oil exporter, investigators began searching for evidence of who was behind the attack.

Although anonymous U.S. officials have been suggesting that Iran was to blame for the Aug. 15 attack, the cyber detectives say the virus’s code had none of the sophisticated elements that would suggest state-sponsored programmers were responsible.

Instead, they said, as the virus spread through the network of the company known as Saudi Aramco, destroying 55,000 computers, the malicious software failed to perform as its designer had intended.

The mistakes in the virus’s code led investigators to the point of attack — a USB stick that had been inserted in a computer on the internal company network — and to the identity of the suspected attacker, an Aramco employee who was logged onto the machine at the time of the incident.

While malware constructed by state-sponsored hackers doesn’t have to be sophisticated, it’s typically far more advanced than the virus used against Saudi Aramco, according to one person involved in the probe who characterized the attack as amateurish. The investigators spoke on condition of anonymity because they weren’t authorized to discuss the attack publicly.

Cyber War

U.S. Defense Secretary Leon Panetta and other American officials have suggested that the Aramco attack is evidence of a brewing global cyber war, one in which countries including Iran are improving their ability to attack commercial and government targets to retaliate against assaults on their own computers, protest U.S. policies or practice a new form of warfare.

Detailed forensic evidence from the Aramco attack and others shows how difficult it is to distinguish cyber warfare and espionage from a bewildering array of threats that includes hacktivists, social malcontents, criminals and others.

The design errors and other aspects of the virus, dubbed Shamoon by researchers, offer some of the strongest evidence that the attack in Saudi Arabia most likely was perpetrated by a single individual, a person involved in the investigation said. The company insider didn’t have the skills or access to penetrate the company’s oil production facilities, which would have been far more devastating, the investigator said.

Nail Al-Jubeir, director of the information office at the Saudi Embassy in Washington, declined to comment, referring questions to Saudi Aramco and the Saudi Interior Ministry, which didn’t immediately respond to e-mails.

Stuxnet Virus

Two U.S. intelligence officials said in interviews that the evidence implicating Iran in the Aramco attack is largely circumstantial, though they declined to discuss it in detail. The attack, they said, does fit a pattern of increased Iranian cyber warfare activity since 2010, after a sophisticated virus known as Stuxnet attacked its main uranium enrichment facilities.

U.S. officials told the New York Times earlier this year that President Barack Obama had ordered joint U.S.-Israeli cyberattacks, code-named Olympic Games, against Iran.

Forensic investigators involved in the Aramco probe, though, aren’t convinced that the incident was an Iranian response to attacks on its suspected nuclear weapons program.

The virus destroyed data on Aramco servers and erased hard- drives on individual computers, replacing critical company data with the image of a burning American flag. It’s considered among the most damaging direct attacks against any corporate information network.

Coding Errors

Parts of the virus used off-the-shelf software, while other elements appear to have been downloaded from hacker forums, according to a participant in the investigation. Errors in the code kept it from overwriting certain segments of Aramco directories that its designer had instructed it to, he said. That allowed analysts to retrieve information that assisted their investigation.

In response to a question from a reporter, Panetta said today that the computer virus that attacked Aramco’s network used “a very sophisticated tool.”

“There are only a few countries in the world that have that capability,” Panetta said at a Pentagon press conference. “But it raises tremendous concerns about the potential for the use of that kind of tool when it comes to our power grid, when it comes to our financial systems, when it comes to our government systems.”

The virus was “one of the first we’ve seen that can actually take and destroy computers,” Panetta said.

Not Exotic

A person who helped investigate the Aramco attack contradicted Panetta’s characterization of the virus as exotic. The investigator said the malware destroyed computers by overwriting the master boot record that computers need to start up. That part of the virus, he said, was taken from an off-the- shelf product made by EldoS Corporation, a London-based security company.

Eugene Mayevski, the company’s chief technology officer, said in an Aug. 17 blog post that the wiper used in the Shamoon virus was a commercial EldoS product called RawDisk and guessed that it “was probably stolen from some of our clients software.”

Iran’s oil industry was hit with a similar data-erasing virus in April, which was dubbed Wiper. Roel Schouwenberg, who examined the viruses independently, says the Wiper virus may have inspired the Aramco technique, but the two don’t use the same code. Schouwenberg is senior researcher for Woburn, Massachusetts-based Kaspersky Lab Inc., a division of Moscow- based Kaspersky Lab.

Middle East

Shamoon also doesn’t share any of its code with Stuxnet or Flame, two of the investigators said. Both of the more-advanced cyber weapons are now in the hands of many nation-states and sophisticated hackers.

“Shamoon really doesn’t have something in common with these operations such as Stuxnet and Flame,” Schouwenberg said. “The only thing it has in common is it’s an attack on critical infrastructure in the Middle East.”

“If Shamoon had happened in Norway, we wouldn’t have been drawing these comparisons,” he said.

Forensic analysis, though, cannot provide definitive proof that an attack wasn’t the work of a nation-state, Schouwenberg said. It’s possible a state actor might make a virus look amateurish in an attempt to cover its tracks.

“Sloppy code may well become more prevalent as a form of obfuscation,” he said.

RasGas Attack

Although pinning the attack on Iran is increasingly popular in Washington, Saudi Arabian social networking sites offer a different theory. They blame the Shiite Muslim minority in the predominantly Sunni country’s oil-rich Eastern Province, where there are religious and economic tensions.

An attack two weeks later against RasGas, a liquified natural gas company in Qatar, underscores the difficulty of sorting out motives and attackers in the shadowy world of cyber conflict.

An investigator who’s familiar with both attacks said the RasGas computer virus shares some characteristics with the one used against Aramco but contains different coding errors. He said it’s possible the RasGas attack was a copycat designed by the attacker to make it look as if the two were linked.

In his Oct. 11 speech to Business Executives for National Security on the deck of the USS Intrepid, a decommissioned aircraft carrier in New York, Panetta said a cyberattack by nation-states or violent extremist groups “could be as destructive as the terrorist attack of 9/11.”

Effective Attack

Without linking the country to any specific attack, he said, “Iran has also undertaken a concerted effort to use cyberspace to its advantage.”

If the flaws in the Aramco virus don’t prove that Iran wasn’t responsible, they also don’t mean the attack wasn’t effective.

The virus not only destroyed the hard drives of more than 60 percent of Aramco’s computers, it also wiped out data on the company’s servers, including the domain management servers that were the heart of the corporate network, said an investigator involved in the clean-up.

Following the attack, a team of investigators and cybersecurity experts flew to Saudi Arabia to help analyze what had happened and develop stronger defenses.

With few answers in the code itself or the nature of the attack, the key to uncovering the culprit and the motive may lie in whatever information is provided by the attacker, a piece of the puzzle missing in other attacks of this scale.

Reports on Saudi social media suggest that the suspected attacker is in custody. One investigator said that there has been an information blackout as to the individual’s motives.

To contact the reporters on this story: Michael Riley in Washington at michaelriley@bloomberg.net; Eric Engleman in Washington at eengleman1@bloomberg.net

To contact the editor responsible for this story: John Walcott at jwalcott9@bloomberg.net