Trickbot Brief: Creds and Beacons

Intro

“TrickBot malware—first identified in 2016—is a Trojan developed and operated by a sophisticated group of cybercrime actors. The cybercrime group initially designed TrickBot as a banking trojan to steal financial data. Through continued development and new functionality, TrickBot has become a highly modular, multi-stage malware that provides its operators a full suite of tools to conduct a myriad of illegal cyber activities. Since TrickBot’s inception, the cybercrime group has used the malware to attack individuals and businesses globally across a wide range of sectors.”

Source – Fact Sheet: TrickBot Malware Source

In an intrusion this past month, threat actors were seen enumerating and collecting information related to the domain as well as dumping passwords before leaving the network. Multiple Cobalt Strike Beacons were deployed and remained connected despite the lack of activity from the threat actors. 

Case Summary

We assess, with moderate confidence, the Trickbot DLL that we executed was originally delivered via a malicious Office document. The threat actors were observed leveraging Trickbot and Cobalt Strike for C2 communication. They began their discovery by running net and nltest commands as well as PowerView domain discovery modules. Minutes later, Lazagne (“retrieve lots of passwords”) was executed using the “all” switch. A registry value was set to enable storing logon credentials in plaintext in memory (WDigest), likely to facilitate future activity as the host was not restarted for this change to take effect. 

Before the threat actors departed the network, they successfully accessed the LSASS process and retrieved credentials from memory. No lateral movement or execution on mission was observed.

Timeline

Analysis and reporting completed by @kostastsale, @ICSNick, and @RoxpinTeddy.

Reviewed by @TheDFIRReport

 

MITRE ATT&CK

Initial Access

We assess with moderate confidence that this DLL was dropped by a malicious Office document. 

Execution

Trickbot (click.php.dll) was manually executed on a single endpoint.

Source: https://tria.ge/210412-wmdnkzp5la 

Trickbot, from its injected wermgr process, spawned a command process to then run a PowerShell Cobalt Strike Beacon.

Reviewing the above PowerShell code, we can extract the shellcode to discover the IP and User-agent string, the beacon will communicate with.

Getting the IP and port using scdbg.

The threat actor also executed a second Cobalt Strike Beacon (wsuC3C.tmp) using the injected wemgr.exe process.

rundll32.exe C:\Users\redacted\AppData\Local\Temp\wsuC3C.tmp,ControlUnitSpeed

Persistence

A scheduled task was created to keep the Trickbot malware persistent on the system.

C:\Windows\system32\rundll32.exe" "C:\Users\redacted\AppData\Roaming\DownloadMngNet5353711913\xxclickdr.dwn",#1

Defense Evasion

Trickbot injected into wermgr.exe processes and used this for communication to command and control infrastructure.

Credential Access

Lazagne was used with the “all” switch, which runs all modules.

Below we can see registry hives being saved to disk.

LSASS was accessed by rundll32, but we did not see anything written to disk.

Trickbot was used to enable the storage of clear text credentials (WDigest) by setting UseLogonCredential to 1.

Key - SYSTEM\ControlSet001\Control\SecurityProviders\WDigest
Value name - UseLogonCredential
Set value data - 1

Discovery

The following net commands were used by the threat actor from the injected Trickbot process. 

net config workstation 
net view /all  
net view /all /domain
net group “Domain Computers” /domain   

The following nltest commands were used by the threat actor from the injected Trickbot process. 

nltest /domain_trusts 
nltest /domain_trusts /all_trusts 

PowerView modules were also used by the threat actor executed from the Cobalt Strike beacons. 

Get-DomainSearcher 
Get-NetComputer 
Get-NetDomain 

The local network was scanned for port 445/SMB. 

ipconfig was used to show all IP info.

ipconfig /all

Command and Control

Trickbot

gtag: rob52 

Cobalt Strike C2 #1 

147.135.78[.]200:80 (Our Threat Feed service has known about this CS service since at least 4-4-2021)

CS Config: 

"x64": {
"md5": "d963ff232b5b519014cbca17e7e9d512",
"sha256": "0f0cf5e9b35012fc51306179ba4c8cfdaa4f60bf293d8140a77a74db548182e5",
"sha1": "77430b1da03bf6fee12d12abd810666a7751e3c0",
"config": {
"HTTP Method Path 2": "/submit.php",
"Method 2": "POST",
"C2 Server": "147.135.78.200,/cx",
"Method 1": "GET",
"Polling": 60000,
"Spawn To x86": "%windir%\\syswow64\\rundll32.exe",
"Beacon Type": "0 (HTTP)",
"Spawn To x64": "%windir%\\sysnative\\rundll32.exe",
"Jitter": 0,
"Port": 80

"x86": {
"md5": "ec2fc2b33d60ddc829c9aeabb6ce0bbe",
"sha256": "93008b078e8358c948877c7fde261231fc72bcd45143132070761550046701f2",
"sha1": "91ea27632c363b821d8f84b8320b1d76f1d91899",
"config": {
"HTTP Method Path 2": "/submit.php",
"Method 2": "POST",
"C2 Server": "147.135.78.200,/push",
"Method 1": "GET",
"Polling": 60000,
"Spawn To x86": "%windir%\\syswow64\\rundll32.exe",
"Beacon Type": "0 (HTTP)",
"Spawn To x64": "%windir%\\sysnative\\rundll32.exe",
"Jitter": 0,
"Port": 80

Cobalt Strike C2 #2 

23.108.57[.]39:443 (Our Threat Feed service has known about this CS service since at least 4-12-2021)
wideri[.]com 

JA3s:ae4edc6faf64d08308082ad26be60767 
JA3:a0e9f5d64349fb13191bc781f81f42e1 
Certificate:[10:cd:12:74:dc:9d:3d:15:b5:e9:f1:f1:22:e1:ff:65:77:a3:c9:93] 
Not Before: 2021/04/04 00:00:00   
Not After: 2022/04/04 23:59:59   
Issuer Org: Sectigo Limited  
Subject Common: wideri.com  
Public Algorithm:rsaEncryption 
JARM:07d14d16d21d21d07c42d41d00041d58c7162162b6a603d3d90a2b76865b53 

CS Config: 

"x64": {
"time": 1618262029857.8,
"config": {
"Jitter": 46,
"Spawn To x86": "%windir%\\syswow64\\wusa.exe",
"Beacon Type": "8 (HTTPS)",
"Method 1": "GET",
"Method 2": "POST",
"C2 Server": "wideri.com,/tab_shop.css",
"Spawn To x64": "%windir%\\sysnative\\wusa.exe",
"Port": 443,
"Polling": 5000,
"HTTP Method Path 2": "/language"
},
"md5": "249f38615a76d47892fc530102a8a178",
"sha256": "91d6230999853424f158fd58bd343c781fd687c71173ee39ed98429181d3cdb4",
"sha1": "9b1f5d93af2344529b37055af8e3db0d3867c5bc"

"x86": {
"time": 1618262025634.5,
"config": {
"Jitter": 46,
"Spawn To x86": "%windir%\\syswow64\\wusa.exe",
"Beacon Type": "8 (HTTPS)",
"Method 1": "GET",
"Method 2": "POST",
"C2 Server": "wideri.com,/language.css",
"Spawn To x64": "%windir%\\sysnative\\wusa.exe",
"Port": 443,
"Polling": 5000,
"HTTP Method Path 2": "/sq"
},
"md5": "46a3380418ce59563c3adfa8f6624d3f",
"sha256": "8cf43734e0d187aaad93e950646a883820b20ca2837480c1140e1751cf6557b2",
"sha1": "44e19c7f2534226e6774591713fbd659931d2e10"

Impact

Aside from the initial compromise on the beachhead host and the stolen credentials, no further impact was observed during this intrusion. No lateral movement or execution on mission was observed.

IOCs

Network

Cobalt Strike:  

147.135.78.200|80  
23.108.57.39|443
wideri[.]com 
http://172.82.179.170/w.dll

Trickbot: 

102.68.17.97|443   
103.76.150.14|443  
103.9.188.23|449   
109.185.139.90|449   
138.185.72.142|443   
148.216.32.55|443   
173.81.4.147|443   
182.253.184.130|449   
185.205.250.162|443   
190.122.168.219|443   
196.41.57.46|449   
200.90.11.177|449   
202.166.211.197|443   
31.134.124.90|443   
31.211.85.110|443   
41.77.134.250|443   
5.59.205.32|443   
62.213.14.166|443   
77.95.93.132|449   
78.138.187.231|443  
81.95.45.234|449  
84.21.206.164|449  
85.112.74.178|449  
87.116.151.237|449  
87.76.1.81|449  
89.250.208.42|449  
91.185.236.170|449  
91.225.231.120|443  
96.9.77.142|443 

File

click.php.dll  
8c0d352934271350cfe6c00b7587e8dc8d062817
0ae86e5abbc09e96f8c1155556ca6598c22aebd73acbba8d59f2ce702d3115f8

xxclickdr.dwn 
8c0d352934271350cfe6c00b7587e8dc8d062817
0ae86e5abbc09e96f8c1155556ca6598c22aebd73acbba8d59f2ce702d3115f8

wsuC3C.tmp 
b7d9f3e387021bba138dbe3d153fef4e7e2196ad
97dedd5ca85a13ab1a8910416b13ffd088b1c7e3486d6629a71f5c118d56fbea

lazagne.exe 
75f4115024b5d0818f0696345eef98d92db92118
61deb3a206cc203252418b431f6556e3f7efd9556fc685eeda7281d9baf89851

Detections

Network

ET CNC Feodo Tracker Reported CnC Server group 11
ET MALWARE Trickbot Checkin Response
ET INFO SUSPICIOUS Dotted Quad Host MZ Response

Sigma

https://github.com/SigmaHQ/sigma/blob/084cd39505861188d9d8f2d5c0f2835e4f750a3f/rules/windows/process_creation/win_malware_trickbot_recon_activity.yml

https://github.com/SigmaHQ/sigma/blob/08ca62cc8860f4660e945805d0dd615ce75258c1/rules/windows/process_creation/win_grabbing_sensitive_hives_via_reg.yml

https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/win_susp_powershell_enc_cmd.yml

Yara

/*
YARA Rule Set
Author: The DFIR Report
Date: 2021-04-27
Identifier: Case 3521 Trickbot
Reference: https://thedfirreport.com
*/

/* Rule Set ----------------------------------------------------------------- */

import "pe"

rule click_php {
meta:
description = "files - file click.php.dll"
author = "The DFIR Report"
reference = "https://thedfirreport.com"
date = "2021-04-27"
hash1 = "0ae86e5abbc09e96f8c1155556ca6598c22aebd73acbba8d59f2ce702d3115f8"
strings:
$s1 = "f_+ (Q" fullword wide
$s2 = "'/l~;2m" fullword wide
$s3 = "y'L])[" fullword wide
$s4 = "1!1I1m1s1" fullword ascii
$s5 = "&+B\"wm" fullword wide
$s6 = ">jWR=C" fullword wide
$s7 = "W!\\R.S" fullword wide
$s8 = "r-`4?b6" fullword wide
$s9 = "]Iip!x" fullword wide
$s10 = "!k{l`<" fullword wide
$s11 = "D~C:RA" fullword wide
$s12 = "]{T~as" fullword wide
$s13 = "7%8+8^8" fullword ascii
$s14 = "f]-hKa" fullword wide
$s15 = "StartW" fullword ascii /* Goodware String - occured 5 times */
condition:
uint16(0) == 0x5a4d and filesize < 1000KB and
( pe.imphash() == "8948fb754b7c37bc4119606e044f204c" and pe.exports("StartW") or 10 of them )
}

MITRE

User Execution – T1204
Command and Scripting Interpreter – T1059
PowerShell – T1059.001
Windows Command Shell – T1059.003
Domain Trust Discovery – T1482
Network Service Scanning – T1046
Remote System Discovery – T1018
System Network Configuration Discovery – T1016
System Information Discovery – T1082
Process Injection – T1055
Credentials from Web Browsers – T1555.003
OS Credential Dumping – T1003
LSASS Memory – T1003.001
Exfiltration Over C2 Channel – T1041
Non-Standard Port – T1571

Internal case #3521

The post Trickbot Brief: Creds and Beacons appeared first on The DFIR Report.

Article Link: https://thedfirreport.com/2021/05/02/trickbot-brief-creds-and-beacons/