Cyber attacks by a foreign state resulted in a British company losing £800 million ($1.58 billion) in revenue, the head of MI5 revealed yesterday.
This "was not just through intellectual property loss but also from commercial disadvantage in contractual negotiations", said Jonathan Evans.
"They will not be the only corporate victims. The extent of what is going on is astonishing, with industrial-scale processes involving thousands of people lying behind both state-sponsored cyber espionage and organised cyber crime."
Most state-organised cyber attacks in Britain are believed to be carried out by China and Russia, with an array of targets ranging from weapons manufacturers to petroleum producers.
The director general said the Security Service was involved in the investigation of "cyber-compromises in over a dozen companies and is working with many others that are potential future targets of hostile state activity.
But this is only a tiny proportion of those affected."
Evans also said the rebellions in the Middle East had allowed some members of the global Islamist network created by Osama bin Laden to find bases for exporting jihad. This was a "new and worrying development and could get worse as events unfold".
His comments add to the debate about the backing given by Britain, the United States and European states to opposition movements which have swept away regimes across the region. Critics suggest it is hardline Muslim fundamentalists, fanatically hostile to the West, rather than progressive groups, which have seized the reins of power in the aftermath.
Evans said: "Today, parts of the Arab world have once again become a permissive environment for al-Qaeda. This is the completion of a cycle - al-Qaeda first moved to Afghanistan due to pressure in their Arab countries of origin. They moved to Pakistan after the fall of the Taleban; and now some are heading back home to the Arab world again. A small number of British would-be jihadists are also making their way to Arab countries to seek training and opportunities for militant activity, as they do in Somalia and Yemen. Some will return to the UK and pose a threat here."
Evans said: "The Arab Spring offers the long-term hope of a more pluralistic, democratic and flexible system in the Arab world. If that happens it would ease some of the pressures that have spawned extremism in the region. So we'll have to manage the short-term risks if there is to be a longer-term reward from the Arab Spring."
The Royal United Services Institute says Britain has faced 43 credible terrorist plots since 9/11, with one deemed to be extremely serious every year since then.
Evans said: "In back rooms and in cars and on the streets there is no shortage of individuals talking about wanting to mount terrorist attacks here. We see them regularly in our intelligence investigations. Others in various parts of the world have the same ambition." But he added that successful operations have meant "we are near to reaching a form of stalemate - they haven't stopped trying but we have got better at stopping them."