Lotus Blossom Chrysalis Backdoor

• System User Discovery With Whoami :
  endpoint Endpoint None version:12
  The following analytic detects the execution of `whoami.exe` without any arguments. It leverages data from Endpoint Detection and Response (EDR) agents, focusing on process execution logs. This activity is significant because both Red Teams and adversaries use `whoami.exe` to identify the current logged-in user, aiding in situational awareness and Active Directory discovery. If confirmed malicious, this behavior could indicate an attacker is gathering information to further compromise the system, potentially leading to privilege escalation or lateral movement within the network.


• System Information Discovery Detection :
  endpoint Windows None version:16
  The following analytic identifies system information discovery techniques, such as the execution of commands like `wmic qfe`, `systeminfo`, and `hostname`. It leverages data from Endpoint Detection and Response (EDR) agents, focusing on process execution logs. This activity is significant because attackers often use these commands to gather system configuration details, which can aid in further exploitation. If confirmed malicious, this behavior could allow attackers to tailor their attacks based on the discovered system information, potentially leading to privilege escalation, persistence, or data exfiltration.


• Windows Wmic Systeminfo Discovery :
  endpoint Endpoint None version:5
  The following analytic detects the execution of Windows Management Instrumentation Command-line (WMIC) commands used for computer system discovery on a Windows system. Specifically, it monitors for commands such as “wmic computersystem” that retrieve detailed information about the computer’s model, manufacturer, name, domain, and other system attributes. While these commands are commonly used by administrators for inventory and troubleshooting, they may also be exploited by adversaries to gain insight into the target environment during the reconnaissance phase of an attack. Identifying and alerting on WMIC computer system queries helps security teams recognize unauthorized information gathering and take steps to mitigate potential threats.


• Windows BitDefender Submission Wizard DLL Sideloading :
  endpoint Endpoint None version:3
  Detects DLL side-loading of Bitdefender Submission Wizard (BDSubmit.exe, bdsw.exe, or renamed BluetoothService.exe) when a malicious log.dll is loaded from a non-standard path via Sysmon ImageLoad events.


• Windows Bluetooth Service Installed From Uncommon Location :
  endpoint Endpoint None version:3
  Identifies the creation of a Windows service named "BluetoothService" with a binary path in user-writable directories, particularly %AppData%\Bluetooth. This technique was observed in the Lotus Blossom Chrysalis backdoor campaign, where attackers created a service named "BluetoothService" pointing to a malicious binary (renamed Bitdefender Submission Wizard) in a hidden AppData directory. While legitimate Bluetooth services exist in Windows, they are system services with binaries in System32. Any BluetoothService created with a binary path in user directories (AppData, Temp, Downloads) is highly suspicious and indicates potential malware persistence.


• Windows Rundll32 Execution With Log.DLL :
  endpoint Endpoint None version:3
  Identifies the execution of rundll32 with a command line argument of "log.dll", as used in the Lotus Blossom Chrysalis backdoor campaign. Attackers placed a malicious "log.dll" in "%AppData%\Bluetooth" and invoked it via rundll32.exe "log.dll,LogInit" to decrypt and execute ShellCode. The legitimate Bitdefender Submission Wizard (BDSubmit.exe, bdsw.exe) also uses log.dll and is vulnerable to DLL sideloading.


• Windows TinyCC Shellcode Execution :
  endpoint Endpoint None version:4
  Detects abuse of Tiny-C-Compiler (TinyCC) for shellcode execution, where tcc.exe is renamed to masquerade as svchost.exe and used to compile and execute C source files containing shellcode. This technique was observed in the Lotus Blossom Chrysalis backdoor campaign, where attackers renamed "tcc.exe" to "svchost.exe", and executed a file named "conf.c" containing Metasploit block_api shellcode with the flags -nostdlib -run. TinyCC is a legitimate C compiler, but its ability to compile and execute code on-the-fly makes it attractive to attackers seeking to evade detection. The combination of a renamed compiler binary executing from non-standard locations with suspicious flags is a strong indicator of malicious activity.