We recently discussed some methods for detecting the Log4j exploit, and we’ve now developed another method that everyone running Zeek® or a Corelight sensor can use. Our new approach is based on the rarity of legitimate downloads of Java via LDAP. Zeek does not currently have a native LDAP protocol analyzer (though one is available if you are running Spicy). This will not stop you from detecting this exploit downloading Java over LDAP, though. To see how, read on.

If you’re in tech at all, you’ve likely heard of the Log4Shell exploit taking over the Intertubes. If you’re not a Java developer (or developer of any sort), you may be left scratching your head as to just what’s going on. This post is split into two parts: an explanation of Log4Shell for non-developers and an overview of the Log4Shell vulnerability for non-Java developers.

A new critical vulnerability has been found in log4j, a widely-used open-source utility used to generate logs inside java applications. The vulnerability CVE-2021-44228, also known as Log4Shell, permits a Remote Code Execution (RCE) allowing the attackers to execute arbitrary code on the host. The log4j utility is popular and used by a huge number of applications and companies, including the famous game Minecraft.

The vulnerability, dubbed CVE-2021-43798 impacted the Grafana dashboard, which is used by companies around the world to monitor and aggregate logs and other parameters from across their local or remote networks. The privately reported bug became a leaked zero-day but was first spotted by Detectify Crowdsource hacker Jordy Versmissen on December 2, after which Grafana was notified by Detectify about the bug.

Recent CrowdStrike Intelligence team findings regarding the Log4Shell (CVE-2021-44228, CVE-2021-45046) vulnerabilities indicate wide-ranging impact. CrowdStrike helps protect customers from threats delivered via this vulnerability using both machine learning and indicators of attack (IOAs).

Shortly after the Apache Software Foundation (ASF) released the bug fix for the vulnerability known as Log4Shell or LogJam (CVE-2021-44228), a new vulnerability was discovered in Log4j Java-based logging library, tracked as CVE-2021-45046. While Log4Shell had the maximum CVSS score of 10, this new vulnerability is rated as 3.7, affecting all versions of Log4j between 2.0-beta9 and 2.12.1, as well as between 2.13.0 and 2.15.0.