BPFDoor is a sophisticated backdoor payload targeting Linux systems, designed to enable re-entry into compromised environments, as detailed by the Elastic Security Intelligence & Analytics Team. This malware has been active for over five years, indicating that its operators have remained undetected in numerous networks, utilizing a network of VPS servers and compromised routers in Taiwan to act as a VPN. The research delves into the payload's lifecycle, the use of BPF filters for evasion, and offers insights into detection methods and the complexity of its loader. The Elastic team provides indicators of compromise and emphasizes the importance of monitoring organizational workloads effectively, offering tools like a 14-day trial of Elastic Cloud or a free version of the Elastic Stack for enhanced security.