{"description":"Trending threats, MITRE ATT\u0026CK coverage, and detection metadata. Fed continuously.","feed_url":"https://feed.craftedsignal.io/products/microsoft-.net-framework/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":["Microsoft .NET Framework"],"_cs_severities":["medium"],"_cs_tags":["regasm","application-control-bypass","command-and-control","lolbin"],"_cs_type":"advisory","_cs_vendors":["Microsoft"],"content_html":"\u003cp\u003eThe \u003ccode\u003eregasm.exe\u003c/code\u003e (Assembly Registration Tool) is a legitimate Microsoft-signed binary used for registering .NET assemblies. Adversaries may abuse \u003ccode\u003eregasm.exe\u003c/code\u003e to bypass application control or establish command and control (C2) communication. This activity is detected by monitoring network connections initiated by \u003ccode\u003eregasm.exe\u003c/code\u003e to public IP addresses, excluding connections to known private IP ranges. The LOLBAS project has documented the potential misuse of this binary. This activity is significant as it can be used to proxy malicious commands or download payloads. The detection is based on Sysmon Event ID 3 (Network Connect).\u003c/p\u003e\n\u003ch2 id=\"attack-chain\"\u003eAttack Chain\u003c/h2\u003e\n\u003col\u003e\n\u003cli\u003eThe adversary gains initial access through unspecified means (e.g., phishing, exploit).\u003c/li\u003e\n\u003cli\u003eThe adversary executes \u003ccode\u003eregasm.exe\u003c/code\u003e on the compromised system.\u003c/li\u003e\n\u003cli\u003e\u003ccode\u003eregasm.exe\u003c/code\u003e attempts to establish a network connection to a public IP address.\u003c/li\u003e\n\u003cli\u003eThe connection bypasses typical application control restrictions due to the binary being signed by Microsoft.\u003c/li\u003e\n\u003cli\u003eData is transmitted over the established connection, potentially downloading malicious payloads or sending command execution results.\u003c/li\u003e\n\u003cli\u003eThe adversary uses the connection to maintain remote access and control.\u003c/li\u003e\n\u003cli\u003eFurther malicious activities are executed, such as lateral movement or data exfiltration.\u003c/li\u003e\n\u003c/ol\u003e\n\u003ch2 id=\"impact\"\u003eImpact\u003c/h2\u003e\n\u003cp\u003eA successful attack leveraging \u003ccode\u003eregasm.exe\u003c/code\u003e for network communication could allow an adversary to establish a persistent command and control channel within the environment. This could lead to further compromise, including data exfiltration, deployment of ransomware, or other malicious activities. The number of victims and targeted sectors are currently unknown.\u003c/p\u003e\n\u003ch2 id=\"recommendation\"\u003eRecommendation\u003c/h2\u003e\n\u003cul\u003e\n\u003cli\u003eEnable Sysmon Event ID 3 (Network Connect) logging to collect the necessary network connection data (Sysmon EventID 3).\u003c/li\u003e\n\u003cli\u003eDeploy the Sigma rule \u0026quot;Detect Regasm with Network Connection\u0026quot; to your SIEM and tune for your environment to reduce false positives (Sigma rule).\u003c/li\u003e\n\u003cli\u003eInvestigate any alerts generated by the \u0026quot;Detect Regasm with Network Connection\u0026quot; rule, focusing on the destination IP address and associated processes (Sigma rule).\u003c/li\u003e\n\u003cli\u003eImplement application control policies that monitor and restrict the execution of \u003ccode\u003eregasm.exe\u003c/code\u003e, even though it's a signed binary, especially when network connections are involved.\u003c/li\u003e\n\u003cli\u003eReview endpoint network connection logs for \u003ccode\u003eregasm.exe\u003c/code\u003e to identify any unusual or suspicious connections to external IP addresses.\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-regasm-network/","summary":"The detection of regasm.exe, a Microsoft-signed binary, establishing a network connection to a public IP address (excluding private ranges) may indicate command and control activity or attempts to bypass application control.","title":"Regasm.exe Making External Network Connection","url":"https://feed.craftedsignal.io/briefs/2024-01-regasm-network/"}],"language":"en","title":"CraftedSignal Threat Feed - Microsoft .NET Framework","version":"https://jsonfeed.org/version/1.1"}