Chinese Remote Access Trojan Taidoor



SonicWall Capture Labs Threat Research Team recently observed activity for the Chinese Remote Access Trojan Taidoor. Taidoor is composed of two stages, the loader and RAT module. The loader starts the service and decrypts the second file. The loader uses its export function “MyStart” for the initial infection. The function will allocate memory space for a new file called “svchost.dll”.

Before the new file is called it will have to go through a series of routines to decrypt the contents of the file. The DLL uses RC4 encryption, the key is actually rebuilt using the following sting: “ar1zyAXt7d6556sAsvchUQc2”. Once filtered, the RC4 key will be: “ar1z7d6556sAyAXtUQc2”.

The RC4 algorithm is also used to decrypt the import names and other related strings.

DLL Loader Layer, Static Information:

Checking binary static information… (Not Corrupted)…




RC4 Prefiltered Key:

Dynamic Information:

Looking inside “MyStart” Export Routine:

Creating the RAT module:

Once the svchost dll is allocated in memory it will cycle the exports and located the “Start” export routine in the new dll.

Calling the call routine to start the Remote Access Trojan module:

Network Artifacts:

Command and Control Information:


Supported Systems:

  • Windows 10
  • Windows 8.1
  • Windows 8.0
  • Windows 7
  • Windows Vista

SonicWall, (GAV) Gateway Anti-Virus, provides protection against this threat:

  • GAV: Taidoor.LD


Sample SHA256 Hash: 4a0688baf9661d3737ee82f8992a0a665732c91704f28688f643115648c107d4

Security News
The SonicWall Capture Labs Threat Research Team gathers, analyzes and vets cross-vector threat information from the SonicWall Capture Threat network, consisting of global devices and resources, including more than 1 million security sensors in nearly 200 countries and territories. The research team identifies, analyzes, and mitigates critical vulnerabilities and malware daily through in-depth research, which drives protection for all SonicWall customers. In addition to safeguarding networks globally, the research team supports the larger threat intelligence community by releasing weekly deep technical analyses of the most critical threats to small businesses, providing critical knowledge that defenders need to protect their networks.