Log4j vulnerability continues to stress CISOs

A mockup of the log4j Java library logo
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The Log4j vulnerability was actively exploited by coinminers, remote access trojans (RATs), botnets, ransomware, and advanced persistent threats (APTs) in December 2021, according to Avast's Q4 2021 threat report.

Using the aformentioned vulnerability, malicious attackers can execute code remotely on any targeted computer.

Avast's threat researchers have also observed a revival of the Emotet botnet, as well as an increase in coin mining activity by 40%. Both present risks to consumers and businesses alike, placing CISO departments under greater stress.

The security company's Q4 findings also indicate an increase in adware, technical support scams, subscription scams, and spyware targeting Android users. However, RAT and ransomware activity decreased in Q4.

Avast malware research director Jakub Kroustek said: “Towards the end of the year, the extremely dangerous, ubiquitous, and easy to abuse Log4j vulnerability made CISO departments sweat, and rightly so, as it was weaponized by attackers spreading everything from coinminers to bots to ransomware."

"On the other hand, we are happy to report decreases in RAT, information stealer, and ransomware attacks. RAT activity died down thanks to the holidays, with bad actors even going as far as copying the DcRat remote access Trojan and renaming it 'SantaRat',” added Kroustek.


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Aside from exploiting Log4j, threat actors exploited CVE-2021-40449 vulnerability, which elevates permissions for malicious processes through the Windows kernel driver. Attackers used the aforementioned vulnerability to download and run the MistarySnail RAT, according to Avast.

In addition, a malicious campaign abusing Microsoft Azure and Amazon Web Services (AWS) accounted for high NanoCore and AsyncRat detections. AWS and Azure were used as download servers for malware payloads during the campaign.

Even so, Avast reported a 28% decrease in ransomware risk ratio compared to Q3 2021.