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Aug 03, 2018

Volatility Plugin for Detecting Cobalt Strike Beacon

JPCERT/CC has observed some Japanese organisations being affected by cyber attacks leveraging “Cobalt Strike” since around July 2017. It is a commercial product that simulates targeted attacks [1], often used for incident handling exercises, and likewise it is an easy-to-use tool for attackers. Reports from LAC [2] and FireEye [3] describe details on Cobalt Strike and actors who conduct attacks using this tool.

Cobalt Strike is delivered via a decoy MS Word document embedding a downloader. This will download a payload (Cobalt Strike Beacon), which will be executed within the memory. Since Cobalt Strike Beacon is not saved on the filesystem, whether a device is infected cannot be confirmed just by looking for the file itself. There is a need to look into memory dump or network device logs.

This article is to introduce a tool that we developed to detect Cobalt Strike Beacon from the memory. It is available on GitHub - Feel free to try from the following webpage:

JPCERTCC/aa-tools · GitHub

https://github.com/JPCERTCC/aa-tools/blob/master/cobaltstrikescan.py

Tool details

This tool works as a plugin for The Volatility Framework (hereafter “Volatility”), a memory forensic tool. Here are the functions of cobaltstrikescan.py:

  • cobaltstrikescan: Detect Cobalt Strike Beacon from memory image
  • cobaltstrikeconfig: Detect Cobalt Strike Beacon from memory image and extract configuration

To run the tool, save cobaltstrikescan.py in ”contrib/plugins/malware” folder in Volatility, and execute the following command:

$python vol.py [cobaltstrikescan|cobaltstrikeconfig] –f <memory.image> ––profile=<profile>

Figure 1 shows an example output of cobaltstrikescan. You can see the detected process name (Name) and process ID (PID) indicating where the malware is injected to.

Figure 1: Execution results of cobaltstrikescan
Fig1

Figure 2 shows an example output of cobalrstrikeconfig. Please refer to Appendix A for configuration details for Cobalt Strike Beacon.

Figure 2: Execution results of cobaltstrikeconfig
Fig2

In closing

Actors using Cobalt Strike continue attacks against Japanese organisations. We hope this tool helps detecting the attack in an early stage.

- Takuya Endo

(Translated by Yukako Uchida)

Reference

[1] Strategic Cyber LLC:COBALT STRIKE ADVANCED THREAT TACTICS FOR PANETRATION TESTERS

https://www.cobaltstrike.com/

[2] LAC: New attacks by APT actors menuPass (APT10) observed (Japanese)

https://www.lac.co.jp/lacwatch/people/20180521_001638.html

[3] FireEye: Privileges and Credentials: Phished at the Request of Counsel

https://www.fireeye.com/blog/threat-research/2017/06/phished-at-the-request-of-counsel.html

[4] Cybereason: Operation Cobalt Kitty: A large-scale APT in Asia carried out by the OceanLotus Group

https://www.cybereason.com/blog/operation-cobalt-kitty-apt

Appendix A
Table A: Configuration format
Offset Length Description
0x00 2 index (Refer to Table B)
0x02 2

Data length

1 = 2 byte, 2 = 4 byte, 3 = as specified in 0x04

0x04 2 Data length
0x06 As specified in 0x04 Data
 
Table B: Configuration
Offset Description Remarks
0x01 BeaconType 0=HTTP, 1=Hybrid HTTP and DNS, 8=HTTPS
0x02 Port number  
0x03 Polling time  
0x04 Unknown  
0x05 Jitter Ratio of jitter in polling time (0-99%)
0x06 Maxdns Maximum length of host name when using DNS (0-255)
0x07 Unknown  
0x08 Destination host  
0x09 User agent  
0x0a Path when communicating HTTP_Header2  
0x0b Unknown  
0x0c HTTP_Header1  
0x0d HTTP_Header2  
0x0e Injection process  
0x0f Pipe name  
0x10 Year Stops operating after the specified date by Year, Month, Day
0x11 Month  
0x12 Day  
0x13 DNS_idle  
0x14 DNS_Sleep  
0x1a HTTP_Method1  
0x1b HTTP_Method2  
0x1c Unknown  
0x1d Process to inject arbitrary shellcode (32bit)  
0x1e Process to inject arbitrary shellcode (64bit)  
0x1f Unknown  
0x20 Proxy server name  
0x21 Proxy user name  
0x22 Proxy password  
0x23 AccessType

1 = Do not use proxy server

2 = Use IE configuration in the registry

4 = Connect via proxy server

0x24 create_remote_thread Flag whether to allow creating threads in other processes
0x25 Not in use