Yahoo has confirmed that their ads on European websites were subject to a malware injection attack from Dec 31 to Jan 3.
Hundreds of thousands of Yahoo users in European countries including the UK, France and Romania may have been infected with malware injected into advertising hosted on Yahoo websites.
Dutch company Fox-IT made the discovery at the end of last week, saying users who visited Yahoo would be confronted with advertisements that would direct them to external sites hosting malware that exploits Java security flaws.
The ads were served in iframes by Yahoo's advertising service, and were hosted on external sites. Upon clicking the advertisements, users would be redirected to a selection of other domains, all reporting the same Netherlands-based IP address.
The malware users were faced with include money-grabbing Zeus Trojan, botnet software Andromeda and other malware associated with advertising.
Fox-IT estimates that the traffic to the malware hosts was around 300,000 visits per hour. On the assumption that nine percent of those users would ultimately be infected, the firm says around 27,000 infections could have occurred every hour over the four days the adverts were present.
Yahoo confirmed the news in a statement shared with V3: "From 31 December to 3 January on our European sites, we served some advertisements that did not meet our editorial guidelines – specifically, they spread malware. On January 3, we removed these advertisements from our European sites."
The statement added that users in other regions and those using Apple's Mac OS and mobile devices were not affected. "We will continue to monitor and block any advertisements being used for this activity. We will post more information for our users shortly."
The attack bore a resemblance to the one carried out on the PHP.net website, Fox-IT said. In recent months, popular services including Dropbox and Microsoft Silverlight have found themselves under attack, highlighting the risk businesses face when allowing employees to use personal service on their work devices, or allowing them to bring personal devices into work.
This article was originally published on V3.
Revolutionize your digital marketing campaigns at ClickZ Live San Francisco (August 10-12)!
Educating marketers for over 15 years, our action-packed, educationally-focused agenda offers 9 tracks to cover every aspect of digital marketing. Join over 500 digital marketers and expert speakers from leading brands. Register today!
Michael Passingham joined V3 as a reporter in June 2013. Prior to working at V3, Michael spent time at computing magazine PC Pro. Michael covers IT skills, social media, tech startups and also produces V3's video content.
US Consumer Device Preference Report
Traditionally desktops have shown to convert better than mobile devices however, 2015 might be a tipping point for mobile conversions! Download this report to find why mobile users are more important then ever.
E-Commerce Customer Lifecycle
Have you ever wondered what factors influence online spending or why shoppers abandon their cart? This data-rich infogram offers actionable insight into creating a more seamless online shopping experience across the multiple devices consumers are using.