{"description":"Trending threats, MITRE ATT\u0026CK coverage, and detection metadata. Fed continuously.","feed_url":"https://feed.craftedsignal.io/tags/download-error/feed.json","home_page_url":"https://feed.craftedsignal.io/","items":[{"_cs_actors":[],"_cs_cpes":[],"_cs_cves":[],"_cs_exploited":false,"_cs_has_poc":false,"_cs_poc_references":[],"_cs_products":["ESXi"],"_cs_severities":["medium"],"_cs_tags":["esxi","vmware","download-error","anomaly","black-basta"],"_cs_type":"advisory","_cs_vendors":["VMware"],"content_html":"\u003cp\u003eThis detection focuses on identifying anomalous file download behavior on VMware ESXi hosts. It uses ESXi system logs to detect specific error messages related to failed download attempts. These errors might indicate unauthorized attempts to install or update components like VIBs or scripts, potentially signaling malicious activity such as post-compromise actions or ransomware deployment, as seen in cases like Black Basta. The detection aims to identify potential threats early by monitoring download errors that deviate from normal system administration activities, helping defenders prevent further compromise.\u003c/p\u003e\n\u003ch2 id=\"attack-chain\"\u003eAttack Chain\u003c/h2\u003e\n\u003col\u003e\n\u003cli\u003eAttacker gains initial access to the ESXi host, possibly through credential compromise or exploiting a vulnerability.\u003c/li\u003e\n\u003cli\u003eAttacker attempts to download a malicious VIB package or script to the ESXi host.\u003c/li\u003e\n\u003cli\u003eThe ESXi host attempts to download the file from a remote server.\u003c/li\u003e\n\u003cli\u003eThe download fails due to various reasons, such as network issues, incorrect URL, or access restrictions.\u003c/li\u003e\n\u003cli\u003eThe ESXi host logs an error message indicating the failed download attempt, such as \u0026quot;\u003cem\u003eDownload failed\u003c/em\u003e\u0026quot;, \u0026quot;\u003cem\u003eFailed to download file\u003c/em\u003e\u0026quot;, \u0026quot;\u003cem\u003eFile download error\u003c/em\u003e\u0026quot;, or \u0026quot;\u003cem\u003eCould not download\u003c/em\u003e\u0026quot;.\u003c/li\u003e\n\u003cli\u003eThe attacker may attempt to download the file again, possibly using a different method or URL.\u003c/li\u003e\n\u003cli\u003eIf the download eventually succeeds, the attacker proceeds to install and execute the malicious component.\u003c/li\u003e\n\u003cli\u003eIf the download repeatedly fails, the attacker might pivot to other methods of compromising the ESXi host, such as directly uploading malicious files or exploiting other vulnerabilities.\u003c/li\u003e\n\u003c/ol\u003e\n\u003ch2 id=\"impact\"\u003eImpact\u003c/h2\u003e\n\u003cp\u003eSuccessful exploitation following a failed download attempt may lead to the installation of malicious software on the ESXi host, potentially compromising virtual machines hosted on it. This could lead to data theft, ransomware deployment affecting multiple virtual machines, denial of service, or complete control over the ESXi host and its associated virtual infrastructure. While the detection focuses on \u003cem\u003efailed\u003c/em\u003e downloads, it highlights a potential attempt that requires further investigation, before a potential compromise of critical infrastructure.\u003c/p\u003e\n\u003ch2 id=\"recommendation\"\u003eRecommendation\u003c/h2\u003e\n\u003cul\u003e\n\u003cli\u003eConfigure ESXi hosts to forward syslog output to a centralized logging system like Splunk for comprehensive monitoring, as indicated in the \u0026quot;How to Implement\u0026quot; section.\u003c/li\u003e\n\u003cli\u003eDeploy the Sigma rule provided below to your SIEM and tune for your environment to detect the specific error messages associated with failed downloads.\u003c/li\u003e\n\u003cli\u003eInvestigate any alerts generated by the Sigma rule to determine the root cause of the failed download attempts, focusing on the destination (\u003ccode\u003edest\u003c/code\u003e field) of the attempted download.\u003c/li\u003e\n\u003cli\u003eReview and harden ESXi access controls to prevent unauthorized users from initiating file downloads.\u003c/li\u003e\n\u003cli\u003eMonitor network traffic for suspicious outbound connections from ESXi hosts, especially to unusual or untrusted destinations, complementing the \u003ccode\u003enetwork_connection\u003c/code\u003e Sigma rule below.\u003c/li\u003e\n\u003cli\u003eImplement multi-factor authentication for all ESXi administrative accounts to mitigate credential compromise, the likely initial access vector.\u003c/li\u003e\n\u003c/ul\u003e\n","date_modified":"2024-01-03T12:00:00Z","date_published":"2024-01-03T12:00:00Z","id":"https://feed.craftedsignal.io/briefs/2024-01-esxi-download-errors/","summary":"This detection identifies failed file download attempts on ESXi hosts by looking for specific error messages in system logs, potentially indicating unauthorized attempts to install malicious components or scripts.","title":"Detection of Failed ESXi File Downloads","url":"https://feed.craftedsignal.io/briefs/2024-01-esxi-download-errors/"}],"language":"en","title":"CraftedSignal Threat Feed - Download-Error","version":"https://jsonfeed.org/version/1.1"}