{"description":"Trending threats, MITRE ATT\u0026CK coverage, and detection metadata — refreshed continuously.","feed_url":"https://feed.craftedsignal.io/tags/commandandcontrol/","home_page_url":"https://feed.craftedsignal.io/","items":[{"_cs_actors":[],"_cs_cves":[],"_cs_exploited":false,"_cs_products":["Splunk Enterprise","Splunk Enterprise Security","Splunk Cloud"],"_cs_severities":["high"],"_cs_tags":["cobaltstrike","powershell","beacon","commandandcontrol","windows"],"_cs_type":"advisory","_cs_vendors":["Splunk"],"content_html":"\u003cp\u003eCobalt Strike is a popular commercial penetration testing tool often abused by threat actors for command and control (C2) after initial compromise. This brief focuses on detecting the default PowerShell beacon component of Cobalt Strike, which uses recognizable function and variable names in its scripts. By identifying these default names within PowerShell script block logs, defenders can detect Cobalt Strike activity even if the initial delivery mechanism is unknown. This detection is focused on the default variable names and function names within the tool and as such more sophisticated users of the tool may modify their scripts to evade this detection. This brief will aid in detecting default Cobalt Strike PowerShell beacons, giving defenders a chance to respond quickly.\u003c/p\u003e\n\u003ch2 id=\"attack-chain\"\u003eAttack Chain\u003c/h2\u003e\n\u003col\u003e\n\u003cli\u003eThe attacker gains initial access to a target system through various means (e.g., spear phishing, exploiting a vulnerability).\u003c/li\u003e\n\u003cli\u003eA PowerShell script is executed on the target system, either through direct execution or by being called from another process (cmd.exe, mshta.exe).\u003c/li\u003e\n\u003cli\u003eThe PowerShell script contains default Cobalt Strike PowerShell beacon code, including functions and variables like \u003ccode\u003efunc_get_proc_address\u003c/code\u003e, \u003ccode\u003e$var_unsafe_native_methods\u003c/code\u003e, \u003ccode\u003e$var_gpa.Invoke\u003c/code\u003e, \u003ccode\u003efunc_get_delegate_type\u003c/code\u003e, and \u003ccode\u003e$var_type_builder\u003c/code\u003e.\u003c/li\u003e\n\u003cli\u003eThe script uses these functions and variables to dynamically load and execute malicious code in memory, bypassing traditional file-based antivirus solutions.\u003c/li\u003e\n\u003cli\u003eThe beacon establishes a connection to the attacker\u0026rsquo;s C2 server, allowing for remote command execution.\u003c/li\u003e\n\u003cli\u003eThe attacker uses the C2 connection to perform reconnaissance, move laterally within the network, and escalate privileges.\u003c/li\u003e\n\u003cli\u003eThe attacker deploys additional tools or malware to achieve their objectives, such as data exfiltration or ransomware deployment.\u003c/li\u003e\n\u003cli\u003eThe attacker maintains persistence on the compromised system to ensure continued access.\u003c/li\u003e\n\u003c/ol\u003e\n\u003ch2 id=\"impact\"\u003eImpact\u003c/h2\u003e\n\u003cp\u003eSuccessful exploitation via Cobalt Strike can lead to a complete compromise of the targeted system and potentially the entire network. Attackers can steal sensitive data, deploy ransomware, disrupt business operations, and cause significant financial and reputational damage. While the exact number of victims is unknown, Cobalt Strike is used in a wide range of attacks across various sectors, including healthcare, finance, and government. A successful attack could lead to significant data breaches, system downtime, and regulatory fines.\u003c/p\u003e\n\u003ch2 id=\"recommendation\"\u003eRecommendation\u003c/h2\u003e\n\u003cul\u003e\n\u003cli\u003eEnable PowerShell script block logging (Event ID 4104) on all Windows endpoints to capture the necessary data for detection.\u003c/li\u003e\n\u003cli\u003eDeploy the Sigma rule \u0026ldquo;Detect Default Cobalt Strike PowerShell Beacon\u0026rdquo; to your SIEM and tune for your environment using the included false positive guidance.\u003c/li\u003e\n\u003cli\u003eInvestigate any alerts generated by the Sigma rule, paying close attention to the parent processes and network connections associated with the PowerShell scripts.\u003c/li\u003e\n\u003cli\u003eImplement network segmentation to limit the lateral movement of attackers within the network after initial compromise.\u003c/li\u003e\n\u003cli\u003eReview and update PowerShell execution policies to prevent the execution of unsigned or untrusted scripts.\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-cobalt-strike-powershell-beacon/","summary":"This brief outlines detection strategies for default Cobalt Strike PowerShell beacons, which are used for command and control, by identifying specific function and variable names within PowerShell script block logs.","title":"Detection of Default Cobalt Strike PowerShell Beacon","url":"https://feed.craftedsignal.io/briefs/2024-01-cobalt-strike-powershell-beacon/"}],"language":"en","title":"CraftedSignal Threat Feed — Commandandcontrol","version":"https://jsonfeed.org/version/1.1"}