Hackers are using Yahoo’s advertising servers to distribute malware to hundreds of thousands of users since late last month. 300,000 users per hour were being redirected to malicious websites serving ‘Magnitude Exploit Kit’, that exploits vulnerabilities in Java and installs a variety of different malware. The countries most affected by the exploit kit are Romania, Great Brittain and France. At this time it’s unclear why those countries are most affected, it is likely due to the configuration of the malicious advertisements on Yahoo.com.
Source: https://thehackernews.com/2014/01/yahoo-ad-network-abused-to-redirect.html