More than 30,000 computer hard drives belonging to the world's biggest oil company have been damaged in a cyber attack, an investigation has revealed.
According to sources, Saudi Arabia's national oil company was hit after at least one insider with high-level access allegedly assisted hackers to wreak havoc on the company's network last month.
The attack, using a computer virus known as Shamoon against Saudi Aramco, is one of the most destructive cyber strikes conducted against a single business.
Shamoon spread through the company's network and wiped computer hard drives clean.
Saudi Aramco said damage was limited to office computers and did not affect systems software that might harm technical operations.
But the hackers' apparent access to a mole, willing to take personal risk to help, is seen as a concerning development in the ultra-conservative country where open dissent is banned.
"It was someone who had inside knowledge and inside privileges within the company," a source familiar with the ongoing forensic examination told Reuters.
Hackers from a group called The Cutting Sword of Justice claimed responsibility.
They said the computer virus gave them access to documents from Aramco's computers, and have threatened to release secrets, but so far no documents have been published.
Reports of similar attacks on other oil and gas firms in the Middle East, including in neighbouring Qatar, suggest there may be similar activity elsewhere in the region, although the attacks have not been linked.
The company declined to comment on the investigation's evidence.
The hacking group that claimed responsibility for the attack described its motives as political.
In a posting on an online bulletin board the day the files were wiped, the group said Saudi Aramco was the main source of income for the Saudi government, which it blamed for "crimes and atrocities" in several countries, including Syria and Bahrain.
Riyadh is also sympathetic to mainly Sunni rebels in Syria and believed to be a main provider of materiel in the civil war against the Shia-backed Assad regime.
Saudi Arabia's economy is heavily dependent on oil and it holds 20% of the world's proven reserves.
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