Virus writers target web videos

Security firms are reporting more and more instances of booby-trapped Windows codecs - file compressors - required to play some video formats.

Some of the codecs let users play types of net-based video, but also have spyware and adware wrapped inside.

Others, say experts, are outright fakes that just want to infect victims with data-stealing programs.

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"Everyone is watching movies on their PC," said David Robinson, UK head of security firm Norman Sandbox, "they are downloading the latest, greatest clips."

While sites such as YouTube and Revver try to make it easy to watch video online, many of the downloadable clips posted on the web require extra software, called a codec, to play them.