Several types of malware are being delivered in attacks exploiting the recently disclosed Log4j vulnerability named Log4Shell and LogJam.
Cybersecurity companies have reported seeing cryptocurrency miners being delivered in many attacks, but some threat actors have exploited the vulnerability tracked as CVE-2021-44228 to deliver ransomware, trojans, DDoS malware and other malicious programs.
Botnets that specialize in DDoS attacks have also leveraged the Log4Shell vulnerability, including Mirai, Muhstik, and Elknot.
While many of these threats target Linux systems, Bitdefender also reported seeing attempts to deliver a new file-encrypting ransomware named Khonsari on Windows systems. The company also observed attempts to download the Orcus remote access trojan (RAT).
In addition, some attackers have exploited CVE-2021-44228 to deliver a reverse bash shell, which can be used at a later time for other malicious activities.
Microsoft has observed attempts to install Cobalt Strike payloads that can be used for data theft and lateral movement.
Cisco said it had reports of the vulnerability being exploited by “APT-level actors,” but it has not shared any details.
Companies have seen thousands of IP addresses from all around the world scanning the web for vulnerable systems. It’s worth noting, however, that many of these scans are conducted by cybersecurity firms and researchers.
CVE-2021-44228 came to light on December 6, when a patch was released, but there is evidence that exploitation of the vulnerability may have started on December 1, roughly one week after it was reported to Log4j developers. Mass exploitation started on around December 9, after weaponized proof-of-concept (PoC) exploits became available.
Check Point reported seeing more than 60 variations of the original exploit emerging within 24 hours.
Apache Log4j is a Java-based logging tool that is used by many companies around the world, either through open source libraries or directly embedded in their software. The Log4Shell vulnerability can be easily exploited for remote code execution by sending a specially crafted request to the targeted system.
The request generates a log using Log4j, which leverages the Java Naming and Directory Interface (JNDI) lookup feature to perform a request to an attacker-controlled server, from which it fetches a malicious payload and executes it.