Reassembling Victim Domain Fragments from SUNBURST DNS

We are releasing a free tool called SunburstDomainDecoder today, which is created in order to help CERT organizations identify victims of the trojanized SolarWinds software update, known as SUNBURST or Solorigate.

SunburstDomainDecoder can be fed with DNS queries to avsvmcloud.com in order to reveal the full internal domain names of infected companies and organizations.

UPDATE December 18, 2020 (v1.1)

SunburstDomainDecoder has now been updated to automatically reassemble fragmented domain name segments in order to show the full domain in the output.

UPDATE December 19, 2020 (v1.2)

Domain names that have been base32 encoded, such as domain names with uppercase letters, can now be extracted with SunburstDomainDecoder. The queried SUNBURST subdomains are now also included in the output.

UPDATE December 21, 2020 (v1.6)

Improved parsing of base32 encoded domain names. SUNBURST victim domains like "LKDataCenter.com", "Sunkistgrowers.com" and "BrokenArrow.Local" can now be extracted.

UPDATE December 27, 2020 (v1.7)

Improved reassembly of long domain names, like "CIMBMY.CIMBDomain.com" and "BE.AJINOMOTO-OMNICHEM.AD", that get segmented into multiple parts. Extraction of time stamps and security applications, including "Windows Defender", "Carbon Black", "CrowdStrike", "FireEye", "ESET" and "F-Secure". See Sergei Shevchenko's blog post Sunburst Backdoor, Part III: DGA & Security Software for more details.

UPDATE January 4, 2021 (v1.8)

Security products (WinDefend, ESET etc.) are now included in the summary output at the end. SUNBURST stage2 victims, which accept C2 domains in CNAME responses, are indicated with a "STAGE2" tag. The previous release marked stage2 queries with a "DNSSEC" tag. Improved extraction of truncated base32 domains, such as "*TED.com".

UPDATE January 12, 2021 (v1.9)

DNS queries with encoded timestamps are tagged with either "AVProducts" or "Ping", depending on if they include an update of the installed/running security products and services or not. The summary data at the end has been modified to also show partial domain names, such as "paloaltonetworks*".

UPDATE February 16, 2021 (v2.0)

Slightly faster and even more accurate than previous versions.

Download SunburstDomainDecoder.zip

SUNBURST DNS Traffic

SUNBURST victims, who have installed one of the trojanized SolarWinds Orion software updates, will query for domain names formatted like this:

The "SUBDOMAIN" string has different values for each victim and the second half of this string actually contains an encoded domain name (encrypted with a simple substitution cipher).

RedDrip's decode.py

The RedDrip Team published a SUNBURST DGA decoding script yesterday, which can be used to identify SUNBURST victim organizations like CISCO and Belkin by decoding the domain names encoded in the outgoing DNS queries for subdomains of avsvmcloud.com.

This is what it looks like when RedDrip's decode.py script is fed with domain names from John Bambenek's uniq-hostnames.txt file.

The beauty of this approach is that passive DNS data can be used in order to reliably identify the victims. This is great news for national CERTs, because they typically have readily access to passive DNS data and can use the decoded domain names in order to identify and reach out to victims in their country.

After using the python script provided by ReadDrip Team I noticed two things:

1. The leaked domain names were internal domain names used on the victim organizations' corporate networks. Many of the domains were using the ".local" suffix.
2. Most of the extracted domains were truncated to around 15 bytes, which make it difficult to identify the victim organization.

Truncated Domains Fragmented Domains

I later learned that what seemed to be truncated domains were actually fragmented domains, where long domain names would be split into multiple queries. This revelation turns the output from RedDrip's python tool into an interesting domain name puzzle. At this point I decided to take a closer look at the malicious SolarWinds update I had downloaded from SolarWind's website a few days ago -- yes, that's right the malicious software update "SolarWinds-Core-v2019.4.5220-Hotfix5.msp" (MD5: 02af7cec58b9a5da1c542b5a32151ba1) was actually available for download from SolarWinds' website long after they had been notified about their software being backdoored!

As an example, lets' take a closer look at this DNS query from John Bambenek's passive DNS data:
r1qshoj05ji05ac6eoip02jovt6i2v0c.appsync-api.us-west-2.avsvmcloud.com

This query can be broken down into three parts:

1. r1qshoj05ji05ac6 : What is encoded here???
2. eoip02jovt6i2v0c : Base32 encoded string "city.kingston."
3. .appsync-api.us-west-2.avsvmcloud.com : DNS trailer without encoded data

So, which "City of Kingston", or "Kingston City", should we contact to let them know that they have installed a trojanized SolarWinds update? Is it Kingston Jamaica, City of Kingston NY USA, City of Kingston Ontario Canada, Kingston City Tennessee USA or City of Kingston Australia?

After analyzing the "SolarWinds.Orion.Core.BusinessLayer.dll" file (MD5: b91ce2fa41029f6955bff20079468448) from the "SolarWinds-Core-v2019.4.5220-Hotfix5.msp" I learned that the initial "r1qshoj05ji05ac6" string is representing a unique "GUID" value for the infected machine. This GUID is generated by calculating an MD5 hash of the MAC address of the first active non-Loopback network interface, the domain name and the "MachineGuid" registry key value in "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Cryptography".

This MD5 hash is then squeezed into a tiny 8 byte array by XOR'ing overlapping bytes. The "CreateSecureString" function in the trojanized SolarWinds update then "encrypts" this hash using XOR with a random key, which is prepended to the data. The XOR key and the XOR'ed data is then finally base32 encoded into what makes up the first part of the subdomain to query for. Don't let the SUNBURST source code below fool you, it is actually using base32 encoding with a custom alphabet even though the function is called "Base64Encode";

Image: SUNBURST source code generates a random value between 1 and 127 as XOR key

Each DNS lookup from an infected machine will query for a unique subdomain because a new XOR key will be generated for each request. Luckily for us, this XOR key is provided in each request, so we can use it in order to "decrypt" the subdomain and get the original 8 bytes derived from the MAC+domain+MachineGuid MD5 hash.

The output from my "SunburstDomainDecoder.exe" tool will print the "decrypted" 8 byte GUID in the first column, the decoded victim domain segment or timestamp in the second column and the queried SUNBURST subdomain in the last column. Each DNS query line read from standard input will generate a "GUID DecodedHostname SunburstSubdomain" line on standard output.

The tool then finishes off by outputting the domains that are complete or at least have the last part of their domain intact. Some of these domains are complete because they were short enough to fit in one single SUNBURST DNS query, while others have been pieced together by SunburstDomainDecoder from domain fragments arriving in separate SUNBURST DNS queries.

We can now see that it was "city.kingston.on.ca", (City of Kingston, Ontario, Canada) who had installed a trojanized SolarWinds update.

Download SunburstDomainDecoder

The C# source code and a compiled Windows binary for SunburstDomainDecoder is available here:
https://www.netresec.com/files/SunburstDomainDecoder.zip

The source code and Windows binary is shared under a Creative Commons CC-BY license, which means that you are free to:

• Share : copy and redistribute the material in any medium or format
• Adapt : remix, transform, and build upon the material for any purpose, even commercially.

Running SunburstDomainDecoder on Linux/MacOS

Wanna run SunburstDomainDecoder.exe but not in Windows? No problems, the tool runs perfectly fine in Mono. Another option is to build SunburstDomainDecoder.cs as a .NET core project in Linux.

.NET Reversing

Would you like to verify my findings or learn more about .NET reverse engineering? Cool, then I'd recommend that you download dnSpy in order to reverse engineer the SUNBURST .NET DLL (which can be extracted from the msp installer with 7zip). Or you can have a look at the already extracted OrionImprovementBusinessLayer.cs on GitHub.

Posted by Erik Hjelmvik on Thursday, 17 December 2020 22:30:00 (UTC/GMT)

Tags: #SunburstDomainDecoder​ #SUNBURST​ #SolarWinds​ #Solorigate​ #domain​ #DNS​ #pDNS​ #Windows Defender​ #Carbon Black​ #FireEye​ #ESET​ #F-Secure​ #Trojan​ #avsvmcloud​

Detecting the Pony Trojan with RegEx using CapLoader

This short video demonstrates how you can search through PCAP files with regular expressions (regex) using CapLoader and how this can be leveraged in order to improve IDS signatures.

The EmergingThreats snort/suricata rule mentioned in the video is SID 2014411 “ET TROJAN Fareit/Pony Downloader Checkin 2”.

The header accept-encoding header with quality factor 0 used by the Pony malware is:
Accept-Encoding: identity, *;q=0

And here is the regular expression used to search for that exact header: \r\nAccept-Encoding: identity, \*;q=0\r\n

After recording the video I noticed that the leaked source code for Pony 2.0 actually contains this accept-encoding header as a hard-coded string. Have a look in the redirect.php file, where they set curl’s CURLOPT_HTTPHEADER to this specific string.

Wanna learn more about the intended use of quality factors in HTTP accept headers? Then have a look at section 14.1 of RFC 2616section 5.3.4 of RFC 7231, which defines how to use qvalues (i.e. quality factors) in the Accept-Encoding header.

Finally, I'd like to thank Brad Duncan for running the malware-traffic-analysis.net website, your PCAP files often come in handy!

Update 2018-07-05

I submitted a snort/suricata signature to the Emerging-Sigs mailinglist after publishing this blog post, which resulted in the Emerging Threats signature 2014411 being updated on that same day to include:

Thank you @EmergingThreats for the fast turnaround!

Posted by Erik Hjelmvik on Wednesday, 04 July 2018 07:39:00 (UTC/GMT)

Tags: #video​ #regex​ #malware​ #IDS​ #curl​ #malware-traffic-analysis.net​ #videotutorial​

Zyklon Malware Network Forensics Video Tutorial

Analyzing a Zyklon Trojan with Suricata and NetworkMiner

Resources
https://www.malware-traffic-analysis.net/2017/07/22/index.html
https://github.com/Security-Onion-Solutions/security-onion
https://www.arbornetworks.com/blog/asert/wp-content/uploads/2017/05/zyklon_season.pdf
http://doc.emergingthreats.net/2017930

IOCs
service.tellepizza.com
104.18.40.172
104.18.41.172
Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.3pre) Gecko/20070302 BonEcho/2.0.0.3pre
gate.php
.onion
98:1F:D2:FF:DC:16:B2:30:1F:11:70:82:3D:2E:A5:DC
65:8A:5C:76:98:A9:1D:66:B4:CB:9D:43:5C:DE:AD:22:38:37:F3:9C
E2:50:35:81:9F:D5:30:E1:CE:09:5D:9F:64:75:15:0F:91:16:12:02:2F:AF:DE:08:4A:A3:5F:E6:5B:88:37:D6

Posted by Erik Hjelmvik on Monday, 05 February 2018 07:30:00 (UTC/GMT)

Tags: #Netresec​ #PCAP​ #Trojan​ #video​ #tutorial​ #videotutorial​ #NetworkMiner​ #SecurityOnion​ #Suricata​ #malware​ #network​ #forensics​ #NSM​ #malware_traffic​

Full Disclosure of Havex Trojans

I did a talk on "SCADA Network Forensics" at the 4SICS conference last week, where I disclosed the results from my analysis of the Havex RAT/backdoor.

The Havex backdoor is developed and used by a hacker group called Dragonfly, who are also known as "Energetic Bear" and "Crouching Yeti". Dragonfly is an APT hacker group, who have been reported to specifically target organizations in the energy sector as well as companies in other ICS sectors such as industrial/machinery, manufacturing and pharmaceutical.

In my 4SICS talk I disclosed a previously unpublished comprehensive view of ICS software that has been trojanized with the Havex backdoor, complete with screenshots, version numbers and checksums.

Dale Petersen, founder of Digital Bond, expressed the following request regarding the lack of public information about the software trojanized with Havex:

If the names of the vendors that unwittingly spread Havex were made public, the wide coverage would likely reach most of the affected asset owners.

Following Dale's request we decided to publish the information presented at 4SICS also in this blog post, in order to reach as many affected asset owners as possible. The information published here is based on our own sandbox executions of Havex malware samples, which we have obtained via CodeAndSec and malwr.com. In addition to what I presented at 4SICS, this blog post also includes new findings published by Joel "scadahacker" Langill in version 2.0 of his Dragonfly white paper, which was released just a couple of hours after my talk.

In Symantec's blog post about Havex they write:

Three different ICS equipment providers were targeted and malware was inserted into the software bundles

Trojanized MESA Imaging driver

The first vendor known to have their software trojanized by the Dragonfly group was the Swiss company MESA Imaging, who manufacture industrial grade cameras for range measurements.

Image: Screenshot of trojanized MESA Imaging driver installer from our sandbox execution

eWON / Talk2M

The second vendor to have their software trojanized was the Belgian company eWON, who provide a remote maintenance service for industrial control systems called “Talk2M”.

eWon published an incident report in January 2014 and then a follow-up report in July 2014 saying:

Back in January 2014, the eWON commercial web site www.ewon.biz had been compromised. A corrupted eCatcherSetup.exe file had been uploaded into the CMS (Content Management System) of www.ewon.biz web site. eCatcher download hyperlinks were rerouted to this corrupted file. The corrupted eCatcherSetup.exe contained a malware which could, under restricted conditions, compromise the Talk2M login of the infected user.

Image: Screenshot of trojanized Talk2M eCatcher installer from our sandbox execution

Prior to version 2.0 of Joel's Dragonfly report, eCatcher was the only product from eWON known to be infected with the Havex backdoor. However, Joel's report also listed a product called “eGrabit”, which we managed to obtain a malware sample for via malwr.com.

Image: Screenshot of trojanized eGrabIt installer from our sandbox execution

MB Connect Line

The most recent company known to have their software infected with the Havex backdoor was the German company MB Connect Line GmbH, who are known for their industrial router mbNET and VPN service mbCONNECT24.

MB Connect Line published a report about the Dragonfly intrusion in September 2014, where they write:

On 16th of April 2014 our website www.mbconnectline.com has been attacked by hackers. The files mbCHECK (Europe), VCOM_LAN2 and mbCONFTOOL have been replaced with infected files. These files were available from 16th of April 2014 to 23th of April 2014 for download from our website. All of these files were infected with the known Trojan Virus Havex Rat.

Image: Screenshot of trojanized mbCONFTOOL installer from our sandbox execution

Image: Screenshot of trojanized mbCHECK application from our sandbox execution

Notice how only mbCHECK for users in Europe was trojanized, there has been no report of the USA/CAN version of mbCHECK being infected with Havex.

We have not been able to get hold of a malware sample for the trojanized version of VCOM_LAN2. The screenshot below is therefore from a clean version of this software.

Image: Screenshot VCOM_LAN2 installer

Conclusions on Havex Trojans

The vendors who have gotten their software trojanized by Dragonfly are all European ICS companies (Switzerland, Belgium and Germany). Additionally, only the mbCHECK version for users in Europe was infected with Havex, but not the one for US / Canada. These facts indicate that the Dragonfly / Energetic Bear threat actor seems to primarily target ICS companies in Europe.

Next: Detecting Havex with NSM

Read our follow-up blog post Observing the Havex RAT, which shows how to detect and analyze network traffic from ICS networks infected with Havex.

Posted by Erik Hjelmvik on Monday, 27 October 2014 11:11:00 (UTC/GMT)

Tags: #Havex​ #ICS​ #SCADA​ #Trojan​ #4SICS​