The Fallout exploit kit, a toolkit used to silently deliver ransomware and malware to vulnerable devices, was first identified in September 2018. Between September and December, the toolkit was used to exploit vulnerabilities and deliver GandCrab ransomware and other malicious payloads. Towards the end of the year, the vulnerabilities most commonly exploited were a remote code execution vulnerability in the Windows VBScript engine (CVE-2018-8174) and the use-after-free vulnerability in Adobe Flash Player (CVE-2018-4878).

Around December 27, 2018, Fallout exploit kit activity stopped, but only for a few days. Now the exploit kit is back, and several updates have been made including the addition of HTTPS support, a new landing page format, and PowerShell-based malware downloads. A new exploit has also been added for a zero-day use-after-free Adobe Flash player vulnerability (CVE-2018-15982) which was patched on December 5, 2018: A vulnerability also exploited by the Underminer exploit kit.

The Fallout exploit kit is primarily delivered via malvertising campaigns – malicious adverts on third-party ad networks that are served on a variety of legitimate websites. The adverts redirect users to the exploit kit, which probes for vulnerabilities and exploits them to silently deliver malware or ransomware. The updated version of the Fallout exploit kit is delivering the latest version of GandCrab ransomware, for which there is no free decryptor. In addition to GandCrab ransomware, the Fallout exploit kit is delivering ServHelper, AZORult, TinyNuke, Dridex and Smokebot malware.

The malvertising campaigns used to generate traffic to the exploit kit include TrafficShop, Popcash, RevenueHits, and HookAds. The latter is primarily used on high-traffic adult websites that are visited millions of times a month. Users are redirected to a decoy adult site that contains the exploit kit and would be unaware that anything untoward has happened. If there is an unpatched vulnerability for which fallout has an exploit, the ransomware or malware payload will be silently downloaded.

Exploit kit activity is now much lower than in 2016 when EKs were extensively used to deliver malware, but the latest updates show EKs are still a threat and that they are regularly being updated with the latest exploits.

Exploit kits can only deliver malware if unpatched vulnerabilities are present, so prompt patching is strongly recommended. Users also need to visit the sites hosting the exploit kit. Businesses can prevent users from visiting malicious websites using a web filter.

Web filters use blacklists of websites known to host exploit kits are capable of scanning websites for malicious content. They can also prevent third-party ads from being displayed, thus preventing redirects. Since certain categories of website are often used in malvertising campaigns, adult sites and torrents sites for instance, blocking access to those categories of content with a web filter is also recommended.

For further information on web filtering and how it can protect against web-based attacks, contact the TitanHQ team today.