One of the ways that threat actors download malware is using malvertising. Malvertising is the positioning of malicious adverts on legitimate websites that send visitors to websites where malware is installed. The HookAds malvertising campaign is one such example and those responsible for the campaign have been particularly active recently.

The HookAds malvertising campaign has one aim – to direct people to a website hosting the Fallout exploit kit. An exploit kit is malicious code that operates when a visitor arrives on a web page. The visitor’s computer is explored to determine whether there are any flaws – unpatched software – that can be exploited to silently download files.

In the case of the Fallout exploit kit, users’ devices are explored for several known Windows vulnerabilities. If one is discovered, it is exploited and a malicious payload is installed. Several malware variants are currently being shared via Fallout, including data stealers, banking Trojans, and ransomware.

According to threat analyst nao_sec, two different HookAds malvertising campaigns have been identified: One is being used to broadcast the DanaBot banking Trojan and the other is sending two malware payloads – The Nocturnal data stealer and GlobeImposter ransomware via the Fallout exploit kit.

Exploit kits can only be implemented to deliver malware to unpatched devices, so businesses will only be under threat from of this web-based attack vector if they are not 100% up to date with their patching. Sadly, many businesses are slow to run patches and exploits for new vulnerabilities are frequently uploaded to EKs such as Fallout. Due to this, a security solution is needed to obstruct this attack vector.

The threat actors responsible for the HookAds malvertising campaign are taking advantage of the low prices for advertising blocks on websites by low quality ad networks – those often utilized by owners of online gaming websites, adult sites, and other types of websites that should not be logged onto by employees. While the site owners themselves are not actively working with the threat actors behind the campaign, the malicious adverts are still displayed on their websites along with legitimate ads. The use of a web filter is advisable to mitigate this threat.