On Friday, Fox-IT, a Delft, Netherlands-based computersecurity firm, wrote in a blog that attackers had insertedmalicious ads served by ads.yahoo.com.
In statement on Sunday, a Yahoo spokesman, said: "On Friday,January 3 on our European sites, we served some advertisementsthat did not meet our editorial guidelines, specifically theyspread malware." Yahoo said it promptly removed the bad ads, andthat users of Mac computers and mobile devices were notaffected.
Malware is software used to disrupt a computer's operations,gather sensitive information, or gain access to private computersystems.