An estimated ONE BILLION visits may have occurred at major infected websites, from DEC 2014 through FEB 2015 as documented below. Clicking on a malicious advertising link had the potential to drop the Cryptowall Ransomware agent onto vulnerable systems.
RSA CONFERENCE — San Francisco — Cybercriminals deployed an Adobe Flash Player zero-day exploit embedded in online ads for close to two months in an attack that targeted US users with a ransomware payload, researchers said here today.
The use-after-free vulnerability, CVE 2015-0313, was patched by Adobe on Feb. 2, and the day after, the attack campaign came to a screeching halt, according to researchers at Malwarebytes, which traced the zero-day’s lifecycle after their systems detected the attacks in December of last year. The attackers injected the malware-ridden ads on the websites of Dailymotion, Huffington Post, answers.com, New York Daily News, HowToGeek.com, tagged.com, as well as a handful of other sites.
“A zero-day was under everybody’s nose for two months on top websites,” says Pedro Bustamante, director of special projects for Malwarebytes. Bustamante says the researchers had never before seen a malvertising campaign like this one. The attackers used a popular advertising network, which Malwarebytes did not name but said is ranked as the number one such network by Comscore.
Malwarebytes doesn’t have a head count of victims hit with the ransomware, but traffic to the infected sites reached over 1 billion in February of this year. Not all of those victims obviously were infected–they would have to click on the infected ad, and meet the demographics the attackers were looking for, which were US consumers behind residential IP addresses. The attackers used the HanJuan exploit kit, which was hosted on rotating domains to evade detection. It drops CryptoWall ransomware for click fraud purposes. The attackers appear to be “a highly professional operation” given the use of an 0day for months on high-profile sites, Jerome Segura, senior security researcher at Malwarebytes wrote in a report on the attacks.