A new exploit kit has been detected that is being used to deliver Trojans and GandCrab ransomware. The Fallout exploit kit was unknown until August 2018, when it was identified by security researcher Nao_sec. Nao_sec observed the Fallout exploit kit being used to deliver SmokeLoader – a malware variant whose purpose is to download other types of malware.

Nao_sec determined that once SmokeLoader was installed, it downloaded two further malware variants – a previously unknown malware variant and CoalaBot – A HTTP DDoS Bot that is based on August Stealer code. Since the discovery of the Fallout exploit kit in August, it has since been observed downloading GandCrab ransomware on vulnerable Windows devices by researchers at FireEye.

While Windows users are being targeted by the threat group behind Fallout, MacOS users are not ignored. If a MacOS user encounters Fallout, they are redirected to webpages that attempt to fool visitors into downloading a fake Adobe Flash Player update or fake antivirus software. In the case of the former, the user is advised that their version of Adobe Flash Player is out of date and needs updating. In the case of the latter, the user is advised that their Mac may contain viruses, and they are urged to install a fake antivirus program that the website claims will remove all viruses from their device.

The Fallout exploit kit is installed on webpages that have been compromised by the attacker – sites with weak passwords that have been brute-forced and those that have out of date CMS installations or other vulnerabilities which have been exploited to gain access.

The two vulnerabilities exploited by the Fallout exploit kit are the Windows VBScript Engine vulnerability – CVE-2018-8174 – and the Adobe Flash Player vulnerability – CVE-2018-4878, both of which were identified and patched in 2018.

The Fallout exploit kit will attempt to exploit the VBScript vulnerability first, and should that fail, an attempt will be made to exploit the Flash vulnerability. Successful exploitation of either vulnerability will see GandCrab ransomware silently downloaded.

The first stage of the infection process, should either of the two exploits prove successful, is the downloading of a Trojan which checks to see if certain processes are running, namely: filemon.exe, netmon.exe, procmon.exe, regmon.exe, sandboxiedcomlaunch.exe, vboxservice.exe, vboxtray.exe, vmtoolsd.exe, vmwareservice.exe, vmwareuser.exe, and wireshark.exe. If any those processes are running, no further action will be taken.

If those processes are not running, a DLL will be downloaded which will install GandCrab ransomware. Once files are encrypted, a ransom note is dropped on the desktop. A payment of $499 is demanded per device to unlock the encrypted files.

Exploit kits will only work if software is out of date. Patching practices tend to be better in the United States and Europe, so attackers tend to rely on other methods to install their malicious software in these regions. Exploit kit activity is primarily concentrated in the Asia Pacific region where software is more likely to be out of date.

The best protection against the Fallout exploit kit and other EKs is to ensure that operating systems, browsers, browser extensions, and plugins are kept fully patched and all computers are running the latest versions of software. Companies that use web filters, such as WebTitan, will be better protected as end users will be prevented from visiting, or being redirected to, webpages known to host exploit kits.

To ensure that files can be recovered without paying a ransom, it is essential that regular backups are made. A good strategy is to create at least three backup copies, stored on two different media, with one copy stored securely offsite on a device that is not connected to the network or accessible over the Internet.