Thousands of Yahoo! users have been exposed to malware through malicious advertisements over the past few days, according to research by Dutch security firm Fox-IT.
Malware-tainted ads served from ads.yahoo.com were shown to victims in Romania, Great Britain and France, infecting tens of thousands every hour. The first infection was spotted on 30 December, said the security firm.
Yahoo! said it is aware of the attack, and is blocking the ads. The web firm confirmed that Blighty, France and Romania got the worst of it, and claimed the attack did not affect Asia Pacific, North America and Latin America.
Only a tiny percentage of ads were tainted, but those that were attempted to harness the Magnitude Exploit Kit to fling Java-based exploits against the computers of visiting surfers.
The end goal of the attack was to plant banking Trojans such as ZeuS onto compromised Windows machines, as explained in greater depth on HitManPro’s blog here.
Security watchers have long advised that running Java in the browser is far more trouble than it's worth.
If nothing else, the Yahoo! tainted ad attack illustrates the wisdom of disabling Java in the browser; technology rarely needed to surf most websites. ®