Because the invocation of Log4j tends to be verbose, you may be able to see it in file writes or in command line executions. And if you have it configured, we can also look for evidence of file creation/modification with Log4j in the name or the path. In order to understand the extent of your exposure to this RCE vuln, we can once again rely on process execution logging across your environment, to find evidence of Log4j activity. | cyberchef infield=string outfield=result operation=FromBase64 But Wait – Where Might I Have Log4j?Īs stated above, there are a wide range of applications, frameworks, and tools that can leverage Log4j. On the plus side, this activity is currently being seen as part of the user agent field. However, because we know that adversaries change their IP addresses as frequently as I change my shirt (that’s everyday, btw), this may not be the best way to identify this behavior over the long term. Now this scanning will provide a bunch of IP addresses that can be added to your watchlists. Detecting Log4j 2 RCE in SplunkĬurrently, there is a bunch of network scanning taking place. Once a vulnerable host is identified, there are patches and workarounds available. We will detail this in the next section, but there are a plethora of hosts scanning the internet for potentially vulnerable servers. The request from the attacker must be logged via Log4j.The targeted system must be accessible to the attacker in order to send the malicious payload.The version of Log4j must be >= 2.0-beta9 and It should be noted that scanning is not the same as active exploitation. With that said, there are a few requirements for the exploit chain to be successful, as outlined in the blog post from LunaSec and the Apache Log4j security advisory. In order to trigger this vulnerability, the attacker simply needs to trigger a log event that contains the malicious string. In many cases, system administrators may not even know that Log4j is being used within their environment. In fact, according to Ars Technica, Log4j is used in several popular frameworks such as Apache Struts 2, Apache Solr, Apache Druid, and Apache Flink. There are a wide range of frameworks, applications, and tools that leverage Log4j. Affected organizations should upgrade to Log4j 2.15.0 as soon as possible or apply the appropriate mitigations if upgrading is not possible. The Apache Software Foundation recently released an emergency patch for the vulnerability. The attacker could then execute arbitrary code from an external source. Proof-of-Concept code demonstrates that a RCE (remote code execution) vulnerability can be exploited by the attacker inserting a specially crafted string that is then logged by Log4j. Introduction to Log4j RCEĪ serious vulnerability ( CVE-2021-44228) in the popular open source Apache Log4j logging library poses a threat to thousands of applications and third-party services that leverage this library. Otherwise, read on for a quick breakdown of what happened, how to detect it, and MITRE ATT&CK mappings. If you want just to see how to find detections for the Log4j 2 RCE, skip down to the “detections” sections. You can learn more in the Splunk Security Advisory for Apache Log4j. Splunk is currently reviewing our supported products for impact and evaluating options for remediation and/or or mitigation. Credit to authors and collaborators: Ryan Kovar, Shannon Davis, Marcus LaFerrera, John Stoner, James Brodsky, Dave Herrald, Audra Streetman, Johan Bjerke, Drew Church, Mick Baccio, Lily Lee, Tamara Chacon, Ryan Becwar. For additional resources, check out the Log4Shell Overview and Resources for Log4j Vulnerabilities page.Īuthors and Contributors: As always, security at Splunk is a family business. This blog is a part of Splunk's Log4j response.
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