The London Stock Exchange website was attacked by malware hidden inside an advert on February 28th. The Stock Exchange also had a technology problem on the same day, which meant it was unable to trade and had to deal with an unexpected security problem. The advert was infected with hidden malicious code which when a user clicked on it would have installed malware onto their computers.
Google Safe Browsing showed a warning when visiting the londonstockexchange.com website. Google did remove the warning once the malicious content had been removed.
Source: ID Theft Protect