{"description":"Trending threats, MITRE ATT\u0026CK coverage, and detection metadata — refreshed continuously.","feed_url":"https://feed.craftedsignal.io/tags/theme-file/","home_page_url":"https://feed.craftedsignal.io/","items":[{"_cs_actors":[],"_cs_cves":[],"_cs_exploited":true,"_cs_products":["Splunk Enterprise","Splunk Enterprise Security","Splunk Cloud"],"_cs_severities":["medium"],"_cs_tags":["windows","theme-file","code-execution","credential-theft"],"_cs_type":"threat","_cs_vendors":["Splunk"],"content_html":"\u003cp\u003eThis detection identifies suspicious activity related to Windows theme files. Attackers can leverage theme files, designed for customizing desktop appearances, to achieve remote code execution or perform NTLM coercion attacks. The creation of these files in unusual locations, such as the Desktop, Documents, Downloads, or Temp directories, is not typical user behavior and may signify malicious activity. This activity has been observed in attacks attempting to steal user credentials and execute arbitrary code. The detection is based on Sysmon EventID 11 logs and requires a properly configured Endpoint Detection and Response (EDR) solution and Splunk instance.\u003c/p\u003e\n\u003ch2 id=\"attack-chain\"\u003eAttack Chain\u003c/h2\u003e\n\u003col\u003e\n\u003cli\u003eA user downloads a malicious file, often delivered via phishing or drive-by download, containing a crafted \u003ccode\u003e.theme\u003c/code\u003e file.\u003c/li\u003e\n\u003cli\u003eThe malicious file is saved to a common user directory such as Downloads.\u003c/li\u003e\n\u003cli\u003eThe attacker executes code (e.g., via a script or executable) that creates or copies a specially crafted \u003ccode\u003e.theme\u003c/code\u003e file in a location such as \u003ccode\u003eC:\\Users\\\u0026lt;username\u0026gt;\\Downloads\u003c/code\u003e.\u003c/li\u003e\n\u003cli\u003eThe user or attacker interacts with the \u003ccode\u003e.theme\u003c/code\u003e file, triggering the parsing of its contents.\u003c/li\u003e\n\u003cli\u003eThe crafted \u003ccode\u003e.theme\u003c/code\u003e file contains malicious directives that exploit vulnerabilities to execute arbitrary code or initiate NTLM authentication to a rogue server controlled by the attacker.\u003c/li\u003e\n\u003cli\u003eIf code execution is achieved, the attacker gains control of the user\u0026rsquo;s system.\u003c/li\u003e\n\u003cli\u003eIf NTLM coercion is successful, the attacker captures the user\u0026rsquo;s credentials.\u003c/li\u003e\n\u003cli\u003eThe attacker uses compromised credentials or system control for lateral movement or data exfiltration.\u003c/li\u003e\n\u003c/ol\u003e\n\u003ch2 id=\"impact\"\u003eImpact\u003c/h2\u003e\n\u003cp\u003eSuccessful exploitation via malicious theme files can lead to remote code execution, allowing attackers to gain control over the victim\u0026rsquo;s system. NTLM coercion can result in credential theft, enabling lateral movement and further compromise of the network. The scope of impact depends on the attacker\u0026rsquo;s objectives, but may include data exfiltration, ransomware deployment, or long-term persistence within the environment.\u003c/p\u003e\n\u003ch2 id=\"recommendation\"\u003eRecommendation\u003c/h2\u003e\n\u003cul\u003e\n\u003cli\u003eEnable Sysmon EventID 11 logging to collect file creation events, which is required for the detections to function.\u003c/li\u003e\n\u003cli\u003eDeploy the Sigma rules provided below to your SIEM to detect suspicious theme file creation and tune for your environment.\u003c/li\u003e\n\u003cli\u003eInvestigate any alerts generated by these rules, paying close attention to the process creating the theme file and the user context.\u003c/li\u003e\n\u003cli\u003eImplement strict file download policies to reduce the risk of users downloading and executing malicious files.\u003c/li\u003e\n\u003cli\u003eEducate users about the risks associated with opening untrusted files, especially those with unusual extensions like \u003ccode\u003e.theme\u003c/code\u003e.\u003c/li\u003e\n\u003c/ul\u003e\n","date_modified":"2024-01-03T15:00:00Z","date_published":"2024-01-03T15:00:00Z","id":"/briefs/2024-01-03-windows-theme-file-creation/","summary":"Detects the creation of Windows theme files in unusual locations, such as Desktop, Documents, Downloads, or Temp directories, which can be indicative of remote code execution or NTLM coercion attacks.","title":"Windows Theme File Creation in Unusual Location","url":"https://feed.craftedsignal.io/briefs/2024-01-03-windows-theme-file-creation/"}],"language":"en","title":"CraftedSignal Threat Feed — Theme-File","version":"https://jsonfeed.org/version/1.1"}