A leading computer security company says it has discovered one of the most sophisticated pieces of malicious software ever seen.
Symantec says the bug, named Regin, was probably created by a government and has been used for six years against a range of targets around the world.
Once installed on a computer, it can do things like capture screenshots, steal passwords or recover deleted files.
Experts say computers in Russia, Saudi Arabia and Ireland have been hit most.
It has been used to spy on government organisations, businesses and private individuals, they say.
