Researchers at FireEye have reported that the Angler Exploit Kit has been updated and that it is now capable of bypassing Microsoft’s Enhanced Mitigation Experience Toolkit (EMET) protection – the first time this behavior has been observed in the wild.
Angler Exploit Kit Could be Used to Deliver any Malicious Payload
The Angler exploit kit is being used to exploit vulnerabilities in Silverlight and Adobe Flash plug-ins. If vulnerabilities are found, Angler downloads its malicious payload: TeslaCrypt ransomware. Teslacrypt was closed down a few weeks ago and the authors released a universal decryption key that can unlock all infections. Anti-virus firms have since developed tools that can be used to remove TeslaCrypt infections. However, it is probable that the Angler exploit kit will be updated to deliver other malicious payloads for which there is no known fix. Many distributors of TeslaCrypt have already transitioned to CryptXXX.
Currently EMET protections are only being bypassed on devices running Windows 7, although it is probable that attackers will soon develop EMET bypasses that work on more recent versions of Windows. That said, updating to later versions of Windows will help organizations improve their security posture. If an upgrade is not possible or practical, sys admins should ensure that patches are applied promptly. If possible, ActiveX should also be disabled as should Flash and Silverlight plugins. Uninstalling unnecessary software and disabling plugins will reduce the attack surface.
EMET was developed to prevent malicious actors from exploiting memory corruption vulnerabilities, and while this has proved effective at some preventing attacks, the bypass shows that Microsoft’s protection is not 100% effective. While EMET can be used to reduce the risk of ransomware and other malware infections, system admins should not rely on EMET alone. Multi-layered security defenses should be employed to keep networks protected, as this bypass clearly shows. It is still essential to use anti-virus and anti-malware software and to keep definitions up to date.
While efforts can be made to prevent exploit kits from taking advantage of vulnerabilities in plugins, enterprises can reduce risk further by stopping end users from visiting websites known to host exploit kits. By implementing a web filtering solution and restricting access to certain categories of website, enterprises can greatly enhance their security posture.