Hackers are using the Angler exploit kit to automatically spread malware using a vulnerability in the Microsoft Silverlight service.
Malwarebytes senior security researcher Jerome Segura uncovered the attack targeting a vulnerability in Microsoft Silverlight versions 5 and below, warning that it has the potential to infect millions of PCs with malware.
"The flaw, which exists in versions prior to 5.1.20125.0, allows attackers to execute arbitrary code on the affected systems without any user interaction," he said.
"Upon landing on the exploit page, the Angler exploit kit will determine if Silverlight is installed and what version is running. If the conditions are right, a specially crafted library is triggered to exploit the Silverlight vulnerability. As with all exploit kits, leveraging vulnerabilities is just an intermediary step for the real motive: pushing malware onto the victim's machine."
Silverlight is a Microsoft service similar to Adobe Flash, which is used for rich internet applications. The Silverlight web plugin is used by several popular services, including Netflix, which currently boasts over 40 million global users. Segura said he expects hackers to add the Silverlight vulnerability to other exploit kits in the very near future.
"We can expect this CVE [common vulnerability and exposure system] to be integrated into other exploit kits soon, so it is important to make sure you patch all your machines now," he said. "If you don't need Silverlight – or other plugins – simply remove it altogether as that will help to reduce your surface of attack."
Exploit kits are hack tools traded on cyber black markets, which let users automatically mount cyber attacks on known vulnerabilities to spread a variety of malware. The kits have been used in several recent high-profile attacks.
Earlier this year hackers were spotted using the Blackhole exploit kit to mount a sophisticated phishing scam, sending out bogus malware-ridden emails claiming to be from high-profile companies such as Facebook and LinkedIn. Malwarebytes also discovered new ransomware being spread by the Neutrino exploit kit, targeting Java with a fake Skype file.