Last week, the website of a major toy manufacturer was discovered to have been compromised and was being used to infect visitors with ransomware. The website of Maisto was loaded with the Angler exploit kit that probed visitors’ browsers for exploitable vulnerabilities. When vulnerabilities were discovered, they were exploited and ransomware was downloaded onto visitors’ devices. In this case, the ransomware used was CryptXXX.

The website was attacked using JavaScript, which loaded the site with the angler exploit kit. The exploit kit searches for a wide range of browser plugin vulnerabilities that can be exploited. A malware dropper called Bedep is then used to install the ransomware.

Many ransomware infections require a system rebuild and restoration of data from a backup. If a viable backup does not exist there is no alternative but to pat the attackers for an encryption. Fortunately, in this case there is an easy fix for a CryptXXX infection. The ransomware-encrypted files can be decrypted for free according to Kaspersky Lab. However, there are many malicious strains of ransomware that are not so easy to remove.

While decrypting files locked by CryptXXX is possible, that is not the only malicious action performed by the ransomware. CryptXXX is also an information stealer and can record logins to FTP clients, email clients, and steal other data stored in browsers. It can even steal bitcoins from local wallets.

CryptXXX is now being used in at least two major exploit kit attack campaigns according to researchers from Palo Alto Networks. While Locky ransomware was extensively used in March this year – deployed using the Nuclear exploit kit – the attackers appear to have switched to the Angler exploit kit and the Bedep/CryptXXX combo.

How to Block Exploit Kits from Downloading Malware

To protect end users’ devices and networks from malware downloads and to block exploit kits, system administrators must ensure that all browser plugins are kept up to date. Exploit kits take advantage in security vulnerabilities in a wide range of plugins, although commonly vulnerabilities in Flash and Java are exploited. These two browser plugins are used on millions of machines, and new zero-day vulnerabilities are frequently discovered in both platforms. Cybercriminals are quick to take advantage. As soon as a new vulnerability is identified it is rapidly added to exploit kits. Any machine that contains an out-of-date plug in is at risk of attack.

It takes time for patches to be developed and released when a new zero-day vulnerability is discovered. Keeping all devices up to date is a time consuming process and sys admins are unlikely to be able to update all devices the second a patch is released. To effectively protect devices and networks from attacks using exploit kits, consider using a web filtering solution.

A web filter can be used to block websites containing exploit kits and thus prevent the downloading of malware, even if patches have not been installed. The best way to block exploit kits from downloading malware is to ensure that end users never visit a website containing an exploit kit!

A web filter should not be an excuse for poor patch management practices, but web filtering software can ensure devices and networks are much better protected.