Saudi Aramco, the world's biggest oil producer, has resumed operating its main internal computer networks after a virus infected about 30,000 of its workstations in mid-August.





Immediately after the Aug. 15 attack, the company announced it had cut off its electronic systems from outside access to prevent further attacks. Saudi Aramco said the virus "originated from external sources" and that its investigation into the matter was ongoing. There was no mention of whether this was related to this month's Shamoon attacks.





The disruption was suspected to be the result of a virus that had infected personal workstations without affecting the primary components of the network," Saudi Aramco said over " Saudi Aramco said over Facebook





"We would like to emphasize and assure our stakeholders, customers and partners that our core businesses of oil and gas exploration, production and distribution from the wellhead to the distribution network were unaffected and are functioning as reliably as ever," Saudi Aramco's chief executive, Khalid al-Falih, said in a statement.





However, one of Saudi Aramco's websites which was taken offline after the attack - www.aramco.com - remained down yesterday. E-mails sent by Reuters to people within the company continued to bounce back.





Supposed hacktivists have claimed the hit on the oil giant, saying they would hit the company again tomorrow. The group said it was "fed up of crimes and atrocities taking place in various countries around the world", in a post on Pastebin. They said they were targeting the House of Saud, the ruling royal family of Saudi Arabia, and targeted Aramco as it was "the largest financial source for Al-Saud regime".





The group, calling itself the 'Cutting Sword of Justice', claimed to have hacked Aramco systems in several countries before sending a virus across 30,000 computers achieving a 75 percent infection rate of all the company's systems. It refuted suggestions that a nation state was behind the attack.