{"description":"Trending threats, MITRE ATT\u0026CK coverage, and detection metadata — refreshed continuously.","feed_url":"https://feed.craftedsignal.io/tags/vsto/","home_page_url":"https://feed.craftedsignal.io/","items":[{"_cs_actors":[],"_cs_cves":[],"_cs_exploited":false,"_cs_products":["Microsoft Office","Microsoft Visual Studio"],"_cs_severities":["medium"],"_cs_tags":["persistence","office","vsto"],"_cs_type":"advisory","_cs_vendors":["Microsoft"],"content_html":"\u003cp\u003eAttackers can leverage Visual Studio Tools for Office (VSTO) add-ins to establish persistence within Microsoft Office applications. VSTO add-ins, designed to extend the functionality of Office applications, can be manipulated by threat actors to execute malicious code upon application startup. By modifying specific registry keys associated with VSTO add-ins, adversaries can ensure their code is loaded and executed each time an Office application is launched. This technique allows for covert and persistent access to compromised systems, enabling further malicious activities such as data exfiltration, lateral movement, or the deployment of additional payloads. The detection of this persistence mechanism is crucial for defenders to identify and mitigate potential compromises within their environment.\u003c/p\u003e\n\u003ch2 id=\"attack-chain\"\u003eAttack Chain\u003c/h2\u003e\n\u003col\u003e\n\u003cli\u003eAttacker gains initial access to the target system via unspecified means (e.g., phishing, exploiting a vulnerability).\u003c/li\u003e\n\u003cli\u003eThe attacker identifies the registry keys associated with VSTO add-ins for Office applications (Outlook, Word, Excel, PowerPoint). These keys are typically located under \u003ccode\u003e\\Software\\Microsoft\\Office\\[Application]\\Addins\\\u003c/code\u003e.\u003c/li\u003e\n\u003cli\u003eThe attacker modifies the registry to add or modify entries related to a malicious VSTO add-in. This involves setting the \u003ccode\u003eLoadBehavior\u003c/code\u003e value to \u003ccode\u003e3\u003c/code\u003e to ensure the add-in is loaded on startup.\u003c/li\u003e\n\u003cli\u003eThe attacker places the malicious VSTO add-in files (DLLs) in a location accessible to the Office application.\u003c/li\u003e\n\u003cli\u003eThe attacker may also modify the \u003ccode\u003e\\Software\\Microsoft\\VSTO\\Security\\Inclusion\\\u003c/code\u003e registry key to bypass security warnings related to unsigned add-ins.\u003c/li\u003e\n\u003cli\u003eThe user launches the targeted Office application (e.g., Outlook).\u003c/li\u003e\n\u003cli\u003eThe Office application loads the malicious VSTO add-in based on the modified registry entries.\u003c/li\u003e\n\u003cli\u003eThe malicious VSTO add-in executes its payload, enabling the attacker to perform malicious activities on the system.\u003c/li\u003e\n\u003c/ol\u003e\n\u003ch2 id=\"impact\"\u003eImpact\u003c/h2\u003e\n\u003cp\u003eSuccessful exploitation allows attackers to achieve persistent code execution within Microsoft Office applications. This can lead to the compromise of sensitive data, the deployment of additional malware, and the establishment of a long-term foothold within the targeted environment. The scope of impact depends on the privileges of the user account and the capabilities of the malicious VSTO add-in. Since Office applications are commonly used, a successful attack could potentially affect a large number of users within an organization.\u003c/p\u003e\n\u003ch2 id=\"recommendation\"\u003eRecommendation\u003c/h2\u003e\n\u003cul\u003e\n\u003cli\u003eDeploy the Sigma rule \u003ccode\u003ePotential Persistence Via Visual Studio Tools for Office\u003c/code\u003e to your SIEM to detect suspicious registry modifications related to VSTO add-ins.\u003c/li\u003e\n\u003cli\u003eMonitor registry modifications under the paths \u003ccode\u003e\\Software\\Microsoft\\Office\\Outlook\\Addins\\\u003c/code\u003e, \u003ccode\u003e\\Software\\Microsoft\\Office\\Word\\Addins\\\u003c/code\u003e, \u003ccode\u003e\\Software\\Microsoft\\Office\\Excel\\Addins\\\u003c/code\u003e, \u003ccode\u003e\\Software\\Microsoft\\Office\\Powerpoint\\Addins\\\u003c/code\u003e, and \u003ccode\u003e\\Software\\Microsoft\\VSTO\\Security\\Inclusion\\\u003c/code\u003e (see Sigma rule and references).\u003c/li\u003e\n\u003cli\u003eImplement application control policies to restrict the execution of unsigned or untrusted VSTO add-ins.\u003c/li\u003e\n\u003cli\u003eRegularly review and audit installed Office add-ins to identify and remove any suspicious or unauthorized extensions.\u003c/li\u003e\n\u003c/ul\u003e\n","date_modified":"2024-01-03T12:00:00Z","date_published":"2024-01-03T12:00:00Z","id":"/briefs/2024-01-vsto-persistence/","summary":"The Visual Studio Tools for Office (VSTO) add-ins can be abused by attackers to establish persistence in Microsoft Office applications by modifying registry keys.","title":"Persistence via Visual Studio Tools for Office (VSTO) Add-ins","url":"https://feed.craftedsignal.io/briefs/2024-01-vsto-persistence/"}],"language":"en","title":"CraftedSignal Threat Feed — Vsto","version":"https://jsonfeed.org/version/1.1"}