Full Report
This blog will demonstrate the practice and methodology of reversing BugSleep’s protocol, writing a functional C2 server, and detecting this traffic with Snort.
Analysis Summary
# Tool/Technique: BugSleep (MuddyRot) C2 Protocol
## Overview
BugSleep, also known as MuddyRot, is a Remote Access Tool (RAT) that utilizes a bespoke Command and Control (C2) protocol implemented over plain TCP sockets. The analysis focuses on reversing this custom protocol to build a functional C2 server and develop detection signatures using Snort.
## Technical Details
- Type: Malware Family (RAT Implant)
- Platform: Windows (implied by file sample analysis and typical RAT targets)
- Capabilities: Reverse shell, file Input/Output (I/O), persistence capabilities, bespoke encrypted C2 communication.
- First Seen: Analysis based on implants compiled as early as May 8, 2024.
## MITRE ATT&CK Mapping
*Note: Direct mappings are inferred based on stated capabilities (reverse shell, file I/O).*
- T1071 - Application Layer Protocol
- T1071.001 - Web Protocols (Implied application layer communication over TCP)
- T1105 - Ingress Tool Transfer
- (Related to File I/O capabilities for downloading/uploading files)
- T1090 - Proxy
- (Implied if reverse shell is established)
- T1547 - Boot or Logon Autostart Execution
- (Implied via "persistence capabilities")
## Functionality
### Core Capabilities
- **Custom C2 Protocol:** Implements a pseudo-TLV (Type Length Value) structure over plain TCP. Types are limited to integers (4- or 8-byte little-endian) or strings.
- **Data Encryption:** Payloads are encrypted by subtracting a static value (e.g., '3') from each byte of the buffer.
- **Beaconing:** The implant beacons to the C2 server using a `StringMsg` formatted as `ComputerName/Username`.
- **Command Handling:** Commands are executed based on `IntegerMsg` responses following the beacon.
- **Reverse Shell:** Provides remote execution capabilities.
- **File Operations:** Supports `GetFile` (downloading) and `PutFile` (uploading) functionality.
### Advanced Features
- **Bespoke C2 Protocol:** The custom nature of the protocol requires manual analysis (reverse engineering) for interaction.
- **File Obfuscation:** Operators use file-obfuscation techniques to evade detection.
- **File Transfer Chunking:** `GetFile` sends full 1024-byte pages, while `PutFile` transmits data in chunks starting with a 4-byte page number followed by 1020 bytes of file data.
- **Error Handling:** Socket functions (SendSocket/ReadSocket) attempt data transmission/reception 10 times before failing.
- **Emergency Kill:** Responding to the C2 with an `IntegerMsg` of `0x03` causes the implant to terminate, possibly an old kill command remnant.
## Indicators of Compromise
- **File Hashes (SHA256):**
- `b8703744744555ad841f922995cef5dbca11da22565195d05529f5f9095fbfca` (Compile Date: May 8, 2024)
- `94278fa01900fdbfb58d2e373895c045c69c01915edc5349cd6f3e5b7130c472` (Compile Date: May 22, 2024)
- `73c677dd3b264e7eb80e26e78ac9df1dba30915b5ce3b1bc1c83db52b9c6b30e` (Compile Date: May 31, 2024)
- `5df724c220aed7b4878a2a557502a5cefee736406e25ca48ca11a70608f3a1c0` (Compile Date: Jul 7, 2024)
- `960d4c9e79e751be6cad470e4f8e1d3a2b11f76f47597df8619ae41c96ba5809` (Compile Date: Jul 15, 2079 - likely data error/future placeholder)
- **Network Indicators (Defanged C2s):**
- `1[.]235[.]234[.]202`
- `146[.]19[.]143[.]14`
- `46[.]19[.]143[.]14`
- `5[.]239[.]61[.]97`
- **Behavioral Indicators:**
- Communication over plain TCP using the custom pseudo-TLV structure.
- Transmission of beacons formatted as `ComputerName/Username`.
- Traffic exhibiting byte-by-byte XOR subtraction encryption (key = 3).
## Associated Threat Actors
- Not explicitly named in the provided text, but associated with the research detailing the "MuddyRot" implant.
## Detection Methods
- **Signature-based detection:** Snort SIDs 63937 and 63938 cover the identified C2 traffic.
- **Behavioral detection:** Monitoring for traffic matching the specific pseudo-TLV structure and byte subtraction encryption pattern over standard TCP ports.
- **YARA rules:** (Not provided in the article)
## Mitigation Strategies
- Implementing network monitoring tools capable of deep packet inspection to identify traffic deviating from standard application protocols.
- Implementing comprehensive endpoint detection to spot persistence mechanisms utilized by the implant.
- Updating security monitoring solutions with Snort rules 63937 and 63938.
## Related Tools/Techniques
- Other RATs analyzed in related articles include: PowerRAT, DCRAT, ShadowPad, and SpiceRAT.