A Yahoo malware attack hit thousands of users between December 31, 2013 and January 3. The malicious software was eventually traced to advertisements appearing on Yahoo.com. The attack targeted non-mobile Windows users throughout Europe.
Although Yahoo acknowledges the attack, they have not disclosed how many users were affected. Cyber security firm Fox IT estimates nearly 30,000 computers were infected each hour. Surfright, another cyber security firm, estimates a total of 2 million users were hit within three days.
As reported by CNN, users who clicked on the malicious ads were redirected to other sites. The sites contained an "exploit kit," which took advantage of vulnerabilities in Java. Representatives with Yahoo said they identified the issue and "immediately removed it." They confirmed that they "will continue to monitor and block any ads" that are malicious.
A majority of the users hit in the Yahoo malware attack were in France, Great Britain, and Romania, according to Fox IT. Users in Asia, Latin America, and North America were not affected.
Fox IT said the disbursement was "likely due to the configuration of the advertisements." They are unsure who initiated the attack. However, they suspect it was "financially motivated."
Although the extent of the attack is unknown, similar software is capable of granting remote access to personal computers. Remote access allows third parties to access usernames, passwords, and other personal information.
Those who suspect their computers are infected are urged to run a malware scan. Surfright said users with outdated Java Runtime and those who used Yahoo Mail within the last week are "likely infected" and should scan their computer for malicious software.
Representatives from Yahoo said they "take the safety and privacy of [their] users seriously" and will work toward preventing similar attacks in the future. They said the malicious advertisements violated their "editorial guidelines."
The Yahoo malware attack may have affected millions of users. However, Yahoo has not disclosed any details.