Exploit kits have been one of the attack vectors of choice for cybercriminals, although research from Trustwave shows exploit kit activity has been in decline over the past 12 months. Trustwave reports exploit kit activity fell by around 300% over the course of 2016.

Exploit kits are used to probe for vulnerabilities in web browsers and web browser plugins. When a user visits a website hosting an exploit kit, their browser is probed for flaws. If a flaw is found, it is exploited to silently download malware and ransomware.

However, as the middle of the year approached, exploit kit activity started to fall. There are many possible reasons why exploit kit activity has declined. Efforts have increased to make browsers more secure and defenses against exploit kits have certainly been improved.

Adobe Flash vulnerabilities were the most exploited, but last year Adobe started issuing patches faster, limiting the opportunity for the attackers to exploit flaws. The fall in exploit kit activity has also been attributed to the takedown of cybercriminal gangs that extensively used and developed exploit kits. In 2016, the Russian outfit Lurk was broken up and a number of high profile arrests were made. Lurk was the outfit behind the infamous Angler exploit kit. Angler, along with Neutrino, Nuclear and Magnitude were extensively used to download malware and ransomware.

The recently published 2017 IBM X-Force Threat Intelligence Index shows spam email volume increased around the middle of 2016 and there was a marked increase in malicious email attachments. Spam email has now become the attack vector of choice, but that doesn’t mean exploit kits have died. Exploit kits are still being used in attacks, but at a much-reduced level.

Exploit kits are now being used in smaller, more targeted attacks on specific geographical regions, rather than the global attacks using Angler, Nuclear and Magnitude.

Over the past few months, exploit kit activity has started to rise and new exploit kits have been discovered. Late last year, the DNSChanger exploit kit was discovered. While most exploit kits target vulnerabilities in browsers, the DNSChanger exploit kit targets vulnerabilities in routers.

Researchers from Zscaler’s ThreatLabz report there has been an increase in exploit kit activity in the first quarter of 2017. The researchers have noticed a new KaiXin campaign and Neutrino activity has increased. The researchers also detected a new exploit kit called Terror. The Terror exploit kit has been compiled from other exploit kits such as Sundown. The RIG EK continues to be one of the most commonly used kits and has been found to be delivering the ransomware variants Cerber and Locky.

Malicious email attachments may still be the attack vector of choice for spreading ransomware and malware payloads, but the threat from exploit kits is still significant and should not be ignored.

To find out how you can improve your defenses against exploit kits, contact the TitanHQ team today.