{"description":"Trending threats, MITRE ATT\u0026CK coverage, and detection metadata — refreshed continuously.","feed_url":"https://feed.craftedsignal.io/tags/bootkit/","home_page_url":"https://feed.craftedsignal.io/","items":[{"_cs_actors":[],"_cs_cves":[{"cvss":8.2,"id":"CVE-2024-7344"}],"_cs_exploited":false,"_cs_products":["Splunk Enterprise","Splunk Enterprise Security","Splunk Cloud"],"_cs_severities":["high"],"_cs_tags":["bootkit","persistence","efi","bootloader","windows"],"_cs_type":"advisory","_cs_vendors":["Microsoft","Splunk"],"content_html":"\u003cp\u003eThis detection identifies suspicious activity related to the modification of EFI bootloader files on Windows systems. The EFI bootloader files, specifically \u003ccode\u003ebootmgfw.efi\u003c/code\u003e and \u003ccode\u003ebootx64.efi\u003c/code\u003e located in the \u003ccode\u003e\\EFI\\Boot\\\u003c/code\u003e directory, are critical components responsible for initializing the Windows Boot Manager during system startup. Modification or replacement of these files is highly unusual under normal circumstances. Such activity may indicate an attacker\u0026rsquo;s attempt to install a bootkit, establish persistence for malicious code at the firmware level, or otherwise compromise the integrity of the system\u0026rsquo;s boot process. The referenced HybridPetya ransomware and CVE-2024-7344 highlight the real-world threat of bootloader modification for malicious purposes.\u003c/p\u003e\n\u003ch2 id=\"attack-chain\"\u003eAttack Chain\u003c/h2\u003e\n\u003col\u003e\n\u003cli\u003eInitial access is gained through an existing vulnerability or compromised account.\u003c/li\u003e\n\u003cli\u003eThe attacker escalates privileges to obtain necessary permissions to modify system files.\u003c/li\u003e\n\u003cli\u003eThe attacker locates the EFI bootloader files (\u003ccode\u003ebootmgfw.efi\u003c/code\u003e or \u003ccode\u003ebootx64.efi\u003c/code\u003e) in the \u003ccode\u003e\\EFI\\Boot\\\u003c/code\u003e directory.\u003c/li\u003e\n\u003cli\u003eThe attacker modifies the bootloader file, potentially injecting malicious code or replacing it with a compromised version.\u003c/li\u003e\n\u003cli\u003eThe system is rebooted, and the modified bootloader executes, initiating the malicious payload.\u003c/li\u003e\n\u003cli\u003eThe malicious payload gains control early in the boot process, bypassing security measures.\u003c/li\u003e\n\u003cli\u003eThe attacker achieves persistence, allowing them to maintain control over the system even after reboots.\u003c/li\u003e\n\u003c/ol\u003e\n\u003ch2 id=\"impact\"\u003eImpact\u003c/h2\u003e\n\u003cp\u003eSuccessful modification of the EFI bootloader can result in a complete compromise of the affected system. Attackers can use this technique to install persistent malware, bypass security measures, and potentially gain control over the entire network. This can lead to data theft, system disruption, and other malicious activities. While specific victim numbers are unavailable, the criticality of the boot process means any successful attack can have severe consequences.\u003c/p\u003e\n\u003ch2 id=\"recommendation\"\u003eRecommendation\u003c/h2\u003e\n\u003cul\u003e\n\u003cli\u003eEnable Sysmon Event ID 11 logging to monitor file creation events and activate the provided Sigma rule.\u003c/li\u003e\n\u003cli\u003eDeploy the Sigma rule \u003ccode\u003eWindows EFI Bootloader File Modification\u003c/code\u003e to your SIEM and tune it for your environment to detect bootloader modifications.\u003c/li\u003e\n\u003cli\u003eReview the references provided, including the Bleeping Computer article and the ESET research on CVE-2024-7344, for additional context on bootloader attacks.\u003c/li\u003e\n\u003cli\u003eInvestigate any alerts generated by this rule immediately, as they could indicate a serious compromise.\u003c/li\u003e\n\u003c/ul\u003e\n","date_modified":"2024-01-26T12:00:00Z","date_published":"2024-01-26T12:00:00Z","id":"/briefs/2024-01-efi-bootloader-modification/","summary":"A process writing to critical EFI bootloader files (bootmgfw.efi or bootx64.efi) within the \\EFI\\Boot\\ directory may indicate a bootkit installation, malicious code persistence at the firmware level, or tampering with the system boot process.","title":"Windows EFI Bootloader File Modification Detection","url":"https://feed.craftedsignal.io/briefs/2024-01-efi-bootloader-modification/"}],"language":"en","title":"CraftedSignal Threat Feed — Bootkit","version":"https://jsonfeed.org/version/1.1"}