A leading computer security program has discovered one of the most sophisticated pieces of malicious software ever seen.
The bug, which has been named Regin, was thought to have been created by the government, and has been used for six years against a range of targets around the world.
Once installed, Regin can capture screenshots, steal passwords or recover deleted files.
Experts in Russia, Saudi Arabia and Ireland have been hit the most. The bug has been used to spy on government organisations, businesses and private individuals.
Researchers have said the sophistication of the software indicates that it is a cyber-espionage tool that has been developed by a nation state.
They said it is likely that it took months, if not years, to develop - and the creators have gone to great lengths to cover its tracks.
Security strategist, Sian John said: "It looks like it comes from a Western organisation. It's the level of skill and expertise, the length of time over which it was developed."
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