OdinLdr : Advancing Red Team Stealth And Efficiency With Draugr And Cobalt Strike’s UDRLs

The OdinLdr and Draugr tools, alongside Cobalt Strike’s User-Defined Reflective Loader (UDRL), represent advanced mechanisms for enhancing stealth and flexibility in red team operations.

These tools leverage innovative techniques to bypass endpoint detection and response (EDR) systems and optimize post-exploitation tasks.

Key Features Of OdinLdr And Draugr

1. Synthetic Stackframe for NtApi Calls:

• Both OdinLdr and Draugr utilize synthetic stackframes when making NtApi calls. This approach confuses EDR systems that rely on stackframe-based detection, improving operational security.

1. Beacon Integration:

• OdinLdr employs the BeaconUserData structure to manage memory information for Cobalt Strike’s Beacon payloads. This includes allocating memory for Beacon Object Files (BOFs) and sleep masks.
• The loader allocates a read-write memory region for the virtual Beacon, patches the Import Address Table (IAT) and relocations, and adjusts memory protections for each section. All sections are marked as MASK_TRUE in the allocated memory structure.

1. Post-Exploitation Enhancements:

• Post-exploitation tools like PowerPick, Execute-Assembly, and Mimikatz often rely on reflective DLLs. OdinLdr provides a custom reflective loader to improve stealth during these operations.
• Unlike Beacon, the .rdata section in these loaders is set to read-write instead of read-only.

Considerations For Operational Security (OpSec)

1. Custom Injection:

• While UDRLs enhance DLL mapping stealth, execution behaviors remain detectable. Custom injection techniques, such as process-injection kits with synthetic stackframes, are recommended.

1. Sleep Mask Compatibility:

• OdinLdr supports sleep mask integration via BeaconUserData, ensuring compatibility with sleep encryption mechanisms.

1. Avoiding Indicators of Compromise (IoCs):

• Using AMSI bypasses (amsi_disable) in PowerShell or assembly can trigger IoCs. Implementing hardware breakpoint (HWBP) hooking on AmsiScanBuffer for specific DLLs reduces detection risks.

OpSec Features Of UDRLs

• Synthetic stackframe usage mirrors Draugr’s approach for NtApi calls.
• Memory management through BeaconUserData ensures accurate runtime masking.

These advancements draw inspiration from resources like Sektor7’s training programs and Cobalt Strike’s extensive documentation.