ByteCode MSIL Backdoor AsyncRAT Detection

This rule detects the AsyncRAT backdoor by identifying specific bytecode patterns related to its server communication, data handling, URL opening, and monitoring functionalities. The rule uses two main sets of string conditions, both of which are indicative of AsyncRAT's operational mechanisms. The first set ($read_server_data_v1, $send_v1, and $read_packet_v1_p*) focuses on its core communication and data processing. The second set ($send_v2, $open_url_v2, and $monitoring_v2) targets more advanced features like URL manipulation and system monitoring. The rule also checks for the MZ header (uint16(0) == 0x5A4D) to ensure the scanned file is a Windows executable.