By Graham Smith
Last updated at 6:51 PM on 2nd March 2011

  • The London Stock Exchange, Autotrader and Vue were among those affected

Tens of thousands of people are feared to have had their computers infected by booby-trapped adverts on websites including the London Stock Exchange as the full extent of a cyber-attack which began on Sunday becomes apparent.

The scam, which also involved ads on Autotrader, Vue and six other websites, began on Sunday after cyber-criminals hacked into an ad firm's IT system.

Malicious adverts were then released which caused fake virus warnings to pop-up on computers belonging to those surfing the affected sites.

Bogus warnings: The malicious adverts caused fake security warnings to appear on the screens of people surfing the affected websites

Bogus warnings: The malicious adverts caused fake security warnings to appear on the screens of people surfing the affected websites. They were then asked for payment to remove them

After telling them that their computer was infected, the bogus diagnostic screen asked for payment to remove the 'infection'.

It is thought the scam only affected PC users running Safari, Chrome or Firefox browser.

Some of the websites hosting the malicious ads, including the London Stock Exchange, temporarily closed their sites.

IT managers at the affected advertising company, Unanimis, then spent three hours removing the malware.

'The adverts they chose to modify were not being widely distributed,' David Nelson, operations and IT director at Unanimis told the BBC.

The full extent of the cyber-attack, which began on Sunday, has only come to light today

The full extent of the cyber-attack, which began on Sunday, has only come to light today

'This, coupled with the attack taking place on a Sunday evening, limited how many people fell victim.

'We have to count ourselves lucky in some respects.'

An investigation is taking place into how the cyber-criminals got access to the Unanimis server in the first place, and why the breach was not detected earlier.

The company today declined to identify all the sites that had fallen victim to the hack but said the advertising network - owned by the Orange France Telecom Group - had informed all those affected.

Patrik Runald, senior research manager at Websense, suggested a lot of people had been targeted by the rogue warnings.

'We believe that quite a large number of sites were showing these adverts,' he told the BBC, suggesting the figure could have reached 'tens of thousands'.

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I run Linux Mint ... Should I be worried ? Nope :-)

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I didn't realize people still believed fake virus warnings, they are in the same category as multi-million dollar lottery winnings emanating from Lagos.

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I have AVG antivirus software. A couple of times I have had a warning pop up saying my PC is infected and listing various file names. It even has AVG logo on the warning. It syas I need to allow some file to run to correct it. Just to be safe I immediately shut my PC down and do a restart. I then run a complete scan using my actual AVG software. No viruses are found. In short I think these hackers have the ability to detect what internet safety virus you are running, and then imitate it to get you to run their contaminated file. Always shut your computer down immediately when you get these warnings and then run your antivirus software independently.

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I had something really similar to this called HDD LOW on my computer. Same kind of thing - you need to pay for fake software to get rid of a trojan. There's a youtube video that shows you how to get rid of it - using rkill to stop the virus temporarily and then malwarebytes to remove it. I just wanted to mention it on here in case it pops up on anyone elses computer. Do NOT put in your card details!!!

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when we will start to treat computer/ internet based crime seriously? it messes with peoples lives , not to mention that it is very annoying at least. Get these idiots and punish them severly!!!!!!

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Lowlife who hide behind a computer in order spread viruses to the PCs of people they don't know are sick sick sick. They should be put down.

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