The world's largest oil producer, Saudi Aramco, has finally managed to turn its main internal computer networks after a virus infected about 30,000 of its workstations in mid-August.
The company was shut down by an August 15 cyber attack, and its computer systems were taken off line to prevent further attacks.
According to Reuters, Saudi Aramco said the workstations had now been cleansed of the virus and restored to service.
The hack did not harm oil exploration and production - not affected because they operate on isolated systems.
CEO Khalid al-Falih said in a statement that the company's websites were still offline and emails were still bouncing.
The virus "originated from external sources" and the company is continuing to investigate.
A group called the "Cutting Sword of Justice" claimed responsibility for the attack.
It claimed the company was the main source of income for the Saudi government and was responsible for "crimes and atrocities" in several countries, including Syria and Bahrain.
Saudi Arabia is also supporting Sunni rebels against the Syrian regime of President Bashar al-Assad.