CapLoader 1.9.6 Released

CapLoader now detects even more malicious protocols and includes several new features such as JA4 fingerprints, API support for sharing IOCs to ThreatFox and OSINT lookups of malware families on Malpedia. The new CapLoader 1.9.6 release also comes with several improvements of the user interface, for example interactive filtering of flows and services with regular expressions.

Detection of Malware C2 Protocols

Malware authors continually keep coming up with new C2 protocols for defenders to detect. Luckily we don’t need to manually create protocol signatures for CapLoader, we only need a few examples of traffic for a protocol to generate a statistical model that CapLoader can use to detect that protocol. We call this feature Port Independent Protocol Identification (PIPI).

We’ve added support for detecting of the following protocols in this new release of CapLoader:

Image: Protocols identified in PCAP files with malware traffic from various sandboxes (ANY.RUN, Hybrid-Analysis, Joe Sandbox and Triage)

Our PIPI feature can also detect protocols inside of other protocols, such as Cobalt Strike, DCRat, Emotet, Formbook, Gozi ISFB, GzipLoader and Socks5Systemz which all run on top of HTTP. It is sometimes even possible to identify malicious protocols that use TLS encryption, such as AsyncRAT, Cobalt Strike, Emotet, IcedID or Remcos. However, detection of malicious TLS encrypted protocols is a difficult challenge and might be subject to false positives.

Sharing IOCs to ThreatFox

ThreatFox is a free online service for sharing indicators of compromise (IOCs) from malware. ThreatFox can be queried for a particular malware family, such as RedLine Stealer, and it’ll return a list of URLs, domain names and IP:port pairs used for C2 communication or payload delivery for that malware. You can also query for a domain or IP address to see if it’s a known C2 address of any malware or botnet.

CapLoader has supported OSINT lookup of IP addresses and domains on ThreatFox since the release of version 1.9, but with this release we also add the ability to contribute by sharing IOCs with the infosec community. All you need to do is to enter your ThreatFox API-key in CapLoader’s settings, then right-click a flow, service or alert and select “Submit to ThreatFox”.

Image: Submission of microsoft.net.linkpc[.]net to ThreatFox

If the right-clicked item is an alert for a “Malicious protocol” then CapLoader will automatically populate the Mapledia Name field, as shown in the screenshot (win.loda).

TLS Client Fingerprinting with JA4

John Althouse announced the new JA4+ fingerprint methods a couple of months ago on the FoxIO blog. In short JA4+ is a suite of methods designed to fingerprint implementations of a specific set of protocols, including TLS, HTTP and SSH. As you’ve probably guessed JA4+ is a successor to the JA3 and JA3S hashes that we’ve learned to love (we added JA3 fingerprinting to NetworkMiner in 2019).

Most of the fingerprinting methods in the JA4+ suite are patent pending except for the TLS client fingerprinting method “JA4”, which FoxIO does not have patent claims and is not planning to pursue patent coverage for. We have therefore built a JA4 fingerprinting engine that we’ve included in this CapLoader release. Future releases of NetworkMiner will hopefully also include our JA4 fingerprinting engine.

Image: JA3 and JA4 hashes of Remcos C2 traffic

JA4 is similar to JA3 in many ways, but one essential difference is that JA4 fingerprints are something of a fuzzy hash of the client’s handshake rather than a MD5 hash of the raw fingerprint. JA3’s use of MD5 hashing has received criticism, for example in academic literature, partly due to the inability to see if two JA3 hashes have similar TLS handshakes.

JA4 does use hashes, but instead of just being one big hash it breaks the fingerprint into three separate sections; where the first section is used in its raw (non-hashed) format and the other two sections are hashed separately. Thus, an update of a TLS implementation, which only adds one additional cipher, will increment the cipher counter in the first section of the JA4 fingerprint by one and the ciphers hash (second section) will get a new value. The hash in the last section will remain intact.

In the previous CapLoader screenshot with Remcos C2 traffic we see TLS handshakes that have the same JA3 hash (a85be79f7b569f1df5e6087b69deb493) but the JA4 fingerprints have different values (t13i010400_0f2cb44170f4_5c4c70b73fa0 and t13i010400_0f2cb44170f4_1b583af8cc09). The reason why the last JA4 section is different even though the JA3 hash is the same is because some of these TLS handshakes present a different set of signature algorithms, which is a parameter that isn't being used in JA3.

Alerts Tab

CapLoader’s Alerts tab now includes more alert types than before and each alert has a severity rating graded as follows:

• High = 4
• Medium = 3
• Low = 2
• Info = 1

A typical high-severity alert is when a known malicious protocol is detected, while an “Info” type alert can provide a heads up about traffic from things like coin mining or legitimate remote admin tools. As you can see in the screenshot below the alerts are sorted based on severity to make it easier to prioritize them.

Image: CapLoader alerts for 2023-10-16-IcedID-infection.pcap

Here’s a breakdown of the alerts shown in the CapLoader screenshot above:

• GzipLoader traffic to 104.21.7.13:80 / aptekoagraliy[.]com
• BackConnect XOR traffic to 159.89.124.188:443
• IcedID over TLS traffic to 104.223.118.109:443 / seedkraproboy[.]com
• Port-protocol mismatch (non-TLS traffic to port 443) for 159.89.124.188:443
• Periodic connections every 5 minutes to 151.236.9.107:443 / lazirusairnaf[.]com
• Periodic connections every 5 minutes to 104.223.118.109:443 / seedkraproboy[.]com
• Long running TCP session to 159.89.124.188:443
• Long running TCP session to 104.248.81.48:443 / joekairbos[.]com

All these alerts are indicators of an IcedID infection, including the 5 minute C2 connection interval which I have mentioned before.

Other User Interface Improvements

CapLoader’s “Column Criteria” row filter could previously only be used to filter on columns with a specific value, such as “Protocol = TLS”. This new release of CapLoader additionally allows users to do substring matching with the “contains” keyword and regular expression (regex) matching with the “matching” keyword. In the screenshot below the Column Criteria “Hostname matches \.local$” is used to only show hosts that have a hostname ending with “.local”.

We’ve also added an often asked for feature to CapLoader, namely the ability to switch between different flows in the Transcript window.

The flows you can switch between depends on how the transcript window was opened. A flow transcript opened from the Flows tab will allow switching between the flows that were visible in the list from where the transcript was opened. A transcript opened from any of the other tabs (Services, Hosts or Alerts), on the other hand, allows switching between the different flows for the particular service, host or alert that was opened.

Credits

I would like to thank Nic Cerny, Trent Healy and Fredrik Ginsberg for their input on various improvements that have been implemented in CapLoader 1.9.6.

Updating to the Latest Release

Users who have already purchased a license for CapLoader can download a free update to version 1.9.6 from our customer portal or by clicking “Check for Updates” in CapLoader’s Help menu.

Posted by Erik Hjelmvik on Wednesday, 15 November 2023 12:08:00 (UTC/GMT)

Tags: #CapLoader​ #ThreatFox​ #JA3​ #IcedID​ #GzipLoader​ #regex​

Forensic Timeline of an IcedID Infection

The BackConnect and VNC parsers that were added to NetworkMiner 2.8.1 provide a unique possibility to trace the steps of an attacker with help of captured network traffic from a hacked computer.

In this blog post I use the free and open source version of NetworkMiner to see how GzipLoader downloads IcedID, after which the attacker deploys BackConnect VNC to purchase an iPhone 14 with a stolen credit card and then drops Cobalt Strike on the victim PC.

The analyzed pcap is 2022-10-31-IcedID-with-DarkVNC-and-Cobalt-Strike-full-pcap-raw.pcap from Brad Duncan's malware-traffic-analysis.net blog.

Safety First

I ran NetworkMiner in a Windows Sandbox when analyzing this PCAP file to avoid accidentally infecting my computer with any of the malicious artifacts that NetworkMiner extracts from the network traffic.

Another safe way to analyze Windows malware is to run NetworkMiner in Linux or macOS.

14:47 GzipLoader

This infection starts with GzipLoader (aka “IcedID Downloader”) reaching out to its C2 server on vgiragdoffy[.]com (67.205.184.237:80) to download IcedID.

The “_gat” cookie value in frame number 6 tells us that the victim machine is running a Windows 10 build 19045 (aka 22H2). The long “_u” value contains the victim’s username and hostname in hexadecimal representation and the “__io” value is the logged in user’s SID. NetworkMiner decodes these values from the GzipLoader request and displays them in the Hosts tab.

For more info about the GzipLoader cookie, see IcedID PhotoLoader evolution by Jason Reaves and the eSentire blog post on Gootloader and IcedID.

The response for this GzipLoader request is a 550 kB file (MD5 700c602086590b05dde8df57933c7e68) with a fake gzip header. This file actually contains the IcedID DLL (Odwikp.dll) and license.dat files.

14:47 IcedID

The banking trojan IcedID (aka BokBot) gets launched at 14:47:29 UTC (frame 641) after which it connects to these four IcedID servers used for payload delivery and C2:

• ringashopsu[.]com = 137.184.208.116
• sainforgromset[.]com = 138.68.255.102
• yeloypod[.]hair = 94.140.114.103
• airsaintol[.]beauty = 66.63.168.75

These four IcedID servers all run TLS servers with self signed certificates issued for "localhost" and doing TLS handshakes with JA3S hash ec74a5c51106f0419184d0dd08fb05bc. Both these properties can be used as filters in NetworkMiner's Hosts tab to only display the IcedID C2 servers.

14:59 BackConnect and Keyhole VNC

Shortly after the IcedID C2 traffic has been started the IcedID bot also initiates BackConnect C2 connections to 137.74.104.108 on TCP port 8080 (frame 4505 at 14:59:14 UTC).

The BackConnect C2 server tells the bot to sleep for 60 seconds two times before launching a reverse VNC session with command 0x11 (frame 4530 at 15:01.09 UTC).

15:06 Apple Store

The keylog of the attacker above reveals that the attacker is typing “iphone 14 apple store buy”. The VNC graphics that NetworkMiner extracted from the PCAP file additionally reveal that this was a Google search query typed into an Edge browser.

15:10 Credit Card payment

The attacker proceeds to the Apple Store, puts a black iPhone 14 Plus for $987.99 into the shopping cart, enters a delivery address in West Hartford (US) and then inputs credit card details for the payment.

Luckily, the transaction was denied by Apple Store.

15:12 Reverse Shell

After having failed to buy an iPhone through the hacked computer the attacker instead deploys three reverse shell sessions using the BackConnect C2 channel.

These three commands are issued in the first reverse shell session:

In the second shell session the attacker first runs these three commands:

...and then starts a file manager session through the BackConnect C2 channel.

15:40 Deploy Cobalt Strike

The BackConnect file manager is used to upload a Cobalt Strike binary called P2.dll to "C:\ProgramData\" on the victim computer in frame 144535.

The uploaded P2.dll is then executed by running this command in the reverse shell session (frame 144707):

NetworkMiner extracts this uploaded DLL from the BackConnect network traffic.

As you can see in the screenshot above, the MD5 hash of P2.dll is cc69a31a067b62dda5f2076f8ee335e1. This file is flagged as malicious by most AV vendors (P2.dll on VT). However, none of them label it as Cobalt Strike. Luckily I was able to use Triage's malware config extractor to verify that this was indeed Cobalt Strike (P2.dll on tria.ge). Triage also revealed that the CobaltStrike C2 URL was
clouditsoft[.]com:8008/static-directory/mg.jpg

After the DLL gets executed the victim PC establishes Cobalt Strike beacon C2 connections to clouditsoft[.]com on port 8008 (frame 144715).

15:41 MOAR COBALT STRIKE

The BackConnect Reverse Shell log in NetworkMiner's Parameters tab shows that the attacker also attempted to download Cobalt Strike using PowerShell at 15:41:59 UTC (frame 145176) with this command:

IOC List

• IP:port 67.205.184.237:80 (GzipLoader)
• DNS vgiragdoffy[.]com (GzipLoader)
• MD5 700c602086590b05dde8df57933c7e68 (Fake gzip file)
• MD5 f57ab2e5e5720572d5eb19010ec8dcb4 (IcedID Odwikp.dll from fake gzip)
• MD5 57a9d9acb389bd74a7423a16ef81ac18 (IcedID license.dat from fake gzip)
• DNS ringashopsu[.]com (IcedID C2)
• DNS sainforgromset[.]com (IcedID C2)
• DNS yeloypod[.]hair (IcedID C2)
• DNS airsaintol[.]beauty (IcedID C2)
• IP:port 137.184.208.116:443 (IcedID C2)
• IP:port 138.68.255.102:443(IcedID C2)
• IP:port 94.140.114.103:443 (IcedID C2)
• IP:port 66.63.168.7:443 (IcedID C2)
• JA3S hash ec74a5c51106f0419184d0dd08fb05bc (IcedID C2)
• IP:port 137.74.104.108:8080 (IcedID BackConnect C2)
• MD5 cc69a31a067b62dda5f2076f8ee335e1 (CobaltStrike P2.dll)
• DNS clouditsoft[.]com (CobaltStrike C2)
• IP:port 198.44.140.67:8008 (CobaltStrike C2)

Posted by Erik Hjelmvik on Thursday, 12 October 2023 13:23:00 (UTC/GMT)

Tags: #NetworkMiner​ #IcedID​ #GzipLoader​ #BackConnect​ #VNC​ #CobaltStrike​ #Cobalt Strike​ #Windows Sandbox​ #ec74a5c51106f0419184d0dd08fb05bc​ #JA3S​

NetworkMiner 2.8.1 Released

I am happy to announce the release of NetworkMiner 2.8.1 today!

This new release brings a VNC parser to NetworkMiner, so that screenshots, keystrokes and clipboard data can be extracted from unencrypted VNC traffic. NetworkMiner 2.8.1 additionally includes parsers for command-and-control (C2) protocols used by njRAT, IcedID, QakBot and Bazar. We have also added extraction of files sent using a HTTP PUT request, which is the rare cousin to the more common POST request. NetworkMiner’s Images tab has also been updated to enable filtering based on filename or pixel count.

VNC

NetworkMiner now supports the remote framebuffer (RFB) protocol (RFC 6143), which is the underlying protocol used in VNC software. VNC is used to remotely control another computer with help of a real-time video feed of the remote computer’s screen and the ability to control the remote desktop using a mouse and keyboard.

NetworkMiner reassembles the desktop graphics that get transferred between a VNC client and server to build a local representation of the remote desktop. Screenshots of that desktop then get extracted to disk by NetworkMiner as it gets updated. These desktop screenshots can be viewed in NetworkMiner’s Images tab. NetworkMiner also extracts keystrokes and clipboard data from the VNC traffic and displays them in the Parameters tab.

Limitations in VNC Extraction

Essential configuration of the VNC session is set up in the beginning of each TCP session. NetworkMiner therefore requires analyzed traffic to include this initial setup in order to successfully extract graphics from a VNC session.

Only traffic to TCP ports 5900 and 5901 will be parsed as VNC traffic by the free version of NetworkMiner. Our commercial tool NetworkMiner Professional has the ability to identify VNC traffic regardless of port number, but the free version will fail to extract screenshots from VNC traffic running on non-standard ports.

NetworkMiner’s VNC implementation is currently at an early stage, which is why it might fail to extract screenshots or other data from VNC sessions. If you encounter VNC traffic that NetworkMiner fails to parse, then we’d be very grateful if you would contact us and let us know so that we can improve NetworkMiner’s VNC extraction in future releases.

BackConnect

I have previously outlined the BackConnect protocol used by IcedID, QakBot as well as Bazar. This BackConnect protocol is used by botnet operators to remotely control a victim computer using a form of remote access trojan (RAT). This BackConnect protocol supports features such as tunneling network traffic through the victim’s computer, uploading files and the ability to control the victim’s computer using VNC.

NetworkMiner now has a parser for this BackConnect protocol, which allows analysts to see screenshots, keystrokes and file uploads from when the attacker interacts with the hacked computer. As you might have guessed, NetworkMiner’s VNC parser is reused in order to also parse reverse VNC traffic from BackConnect sessions.

I would like to thank Maxime Thiebaut for releasing his PCAPeek tool, which also reassembles reverse VNC traffic from BackConnect traffic. Maxime’s tool proved that it was possible to extract graphics from this C2 traffic, which motivated me to create a BackConnect VNC parser for NetworkMiner.

BackConnect VNC Replay

To demonstrate NetworkMiner’s reverse VNC reassembly I’d like to use the file “2023-07-26-IcedID-with-Keyhole-VNC-traffic.pcap” from Brad Duncan’s fantastic malware-traffic-analysis.net website. In this traffic the IcedID BackConnect C2 server listens to TCP port 443 on 165.232.175.216.

The screenshot thumbnails from the BackConnect VNC traffic shows that the attacker opens up the Amazon website on the victim’s computer. A copy of the full 1920x1152 screenshot, which NetworkMiner extracted from the VNC traffic, can be viewed here: VNC_73F81C83_230726142247.jpg

The parameters tab in NetworkMiner additionally confirms that the attacker manually typed “amazon.com” into the hacked computer’s web browser.

Limitations in BackConnect Parser

The BackConnect implementation in NetworkMiner 2.8.1 is pretty well tested and even supports the new “encrypted” version of BackConnect that IcedID has been deploying lately (we call it “BackConnect XOR”). NetworkMiner can parse the BackConnect C2 traffic as well as the traffic from modules for reverse VNC, reverse SOCKS, reverse shell and the file manager.

Unfortunately the BackConnect traffic typically runs on TCP ports like 443 or 8080, which are normally used for TLS or web proxies. The free open source version of NetworkMiner normally attempts to interpret traffic to port 443 as TLS and 8080 as HTTP proxy, even though it might be BackConnect. A hardcoded list of 32 verified BackConnect C2 servers, such as 165.232.175.216:443, 137.184.172.23:443 and 185.99.132.16:8080, has therefore been added to NetworkMiner’s source code. This enables NetworkMiner to interpret traffic to those IP:port combinations as BackConnect. Our commercial tool NetworkMiner Professional can identify protocols without relying on the port number though, this enables the “Pro” version to also parse BackConnect traffic to C2 servers that aren’t among the 32 hard coded ones in the source code.

njRAT

njRAT is an old, yet still very popular remote access trojan (RAT). It has been around for at least 10 years (since 2013) and can be used to do things like:

• Steal credentials
• Take screenshots of the desktop
• Start the camera
• Record audio with the microphone
• Start a reverse shell
• Upload or download files
• Execute a file or module
• Capture keystrokes with a keylogger
• Create, read or delete registry keys
• Run a command

I have been teaching students in my network forensics classes how to manually parse njRAT traffic since 2015, but from now on I’ll instead be able to tell them to load the njRAT traffic into NetworkMiner to see what the attacker did on the victim’s computer.

The NetworkMiner parameters and victim PC screenshot above were extracted from 2015-04-22_capture-win4.pcap in StratosphereIPS’ dataset CTU-Malware-Capture-Botnet-120-1. The victim PC desktop screenshot actually came out as a 51x4900 pixel image in NetworkMiner 2.8.1, so I had to manually reorganize the tiles to a 510x490 image instead. I’m planning to add an automatic retiling feature to NetworkMiner to avoid having to do this manually in the future.

Limitations in njRAT Parser

njRAT comes in many different versions, forks and flavors and the protocol even has a field delimiter sequence that can be customized for each njRAT backdoor. I can therefore not guarantee that NetworkMiner will be able to parse traffic from all njRAT sessions, but so far I’ve seen very good results – even when custom field delimiters are being used.

Nevertheless, this trojan has an abundance of features but only the most commonly used ones are implemented in NetworkMiner. More specifically NetworkMiner primarily supports extraction of screenshots, credentials, keylog data, file uploads and downloads. NetworkMiner also extracts exfiltrated metadata about the victim machine and bot, such as the hostname, operating system, logged in user, bot ID, botnet, njRAT version and njRAT install date.

Also, as previously mentioned, NetworkMiner doesn’t yet stitch together tiles of desktop screenshots correctly.

Another limitation is that an njRAT C2 server can be deployed on any TCP port, which might prevent the free version from interpreting the C2 traffic as njRAT. The free version of NetworkMiner currently tries to parse traffic to ports like 1177, 5050, 5552 and a few others as njRAT, while NetworkMiner Professional will automatically recognize the njRAT protocol regardless which port it runs on.

Bug Fixes

We’ve added support for SIP keepalive messages (RFC 5626) in NetworkMiner 2.8.1. NetworkMiner Professional would previously fail to extract VoIP calls, or text messages sent through SIP, if a keepalive packet was sent in the session prior to the call or text message. We have also fixed a bug in NetworkMiner’s CapWap parser.

Upgrading to Version 2.8.1

Users who have purchased NetworkMiner Professional can download a free update to version 2.8.1 from our customer portal, or use the “Check for Updates” feature from NetworkMiner's Help menu. Those who instead prefer to use the free and open source version can grab the latest version of NetworkMiner from the official NetworkMiner page.

Posted by Erik Hjelmvik on Monday, 02 October 2023 11:13:00 (UTC/GMT)

Tags: #NetworkMiner​ #VNC​ #BackConnect​ #IcedID​ #njRAT​

How to Identify IcedID Network Traffic

Brad Duncan published IcedID (Bokbot) from fake Microsoft Teams page earlier this week. In this video I take a closer look at the PCAP file in that blog post.

Note: This video was recorded in a Windows Sandbox to minimize the risk of infecting the host PC in case of accidental execution of a malicious payload from the network traffic.

As I have previously pointed out, IcedID sends beacons to the C2 server with a 5 minute interval. According to Kai Lu’s blog post A Deep Dive Into IcedID Malware: Part 2, this 5 minute interval is caused by a call to WaitForSingleObject with a millisecond timeout parameter of 0x493e0 (300,000), which is exactly 5 minutes.

The IcedID trojan uses a custom BackConnect protocol in order to interact with victim computers through VNC, a file manager or by establishing a reverse shell. There was no IcedID BackConnect traffic in this particular PCAP file though, but several other IcedID capture files published on malware-traffic-analysis.net do contain IcedID BackConnect traffic. For more information on this proprietary protocol, please see our blog post IcedID BackConnect Protocol.

IOC List

Fake Microsoft Teams download page

• URL: hxxp://microsofteamsus[.]top/en-us/teams/download-app/
• MD5: 5dae65273bf39f866a97684e8b4b1cd3
• SHA256: e365acb47c98a7761ad3012e793b6bcdea83317e9baabf225d51894cc8d9e800
• More info: urlscan.io

IcedID GzipLoader

• Filename: Setup_Win_13-02-2023_16-33-14.exe
• MD5: 7327fb493431fa390203c6003bd0512f
• SHA256: 68fcd0ef08f5710071023f45dfcbbd2f03fe02295156b4cbe711e26b38e21c00
• More info: Triage

IcedID payload disguised as fake gzip file

• URL: hxxp://alishabrindeader[.]com/
• MD5: 8e1e70f15a76c15cc9a5a7f37c283d11
• SHA256: 7eb6e8fdd19fc6b852713c19a879fe5d17e01dc0fec62fa9dec54a6bed1060e7
• More info: IcedID GZIPLOADER Analysis by Binary Defense

IcedID C2 communication

• IP and port: 192.3.76.227:443
• DNS: treylercompandium[.]com
• DNS: qonavlecher[.]com
• X.509 certificate SHA1: b523e3d33e7795de49268ce7744d7414aa37d1db
• X.509 certificate SHA256: f0416cff86ae1ecc1570cccb212f3eb0ac8068bcf9c0e3054883cbf71e0ab2fb
• JA3: a0e9f5d64349fb13191bc781f81f42e1
• JA3S: ec74a5c51106f0419184d0dd08fb05bc
• Beacon interval: 5 minutes
• More info: ThreatFox

Network Forensics Training

Check out our upcoming live network forensics classes for more hands-on network forensic analysis. Our current class material doesn’t include any IcedID traffic though, instead you’ll get to investigate C2 traffic from Cobalt Strike, TrickBot, njRAT, Meterpreter and a few others.

Posted by Erik Hjelmvik on Wednesday, 15 February 2023 10:52:00 (UTC/GMT)

Tags: #IcedID​ #CapLoader​ #Video​ #Periodicity​ #GzipLoader​ #a0e9f5d64349fb13191bc781f81f42e1​ #ec74a5c51106f0419184d0dd08fb05bc​

IcedID BackConnect Protocol

This is a follow-up to my Hunting for C2 Traffic video. But I didn't have time to record a short video this time, so I wrote a long blog post instead.

UPDATE 2022-11-02

Brad Duncan has released a new pcap file on malware-traffic-analysis.net, which contains an additional C2 command (0x12). Our analysis indicates that this command launches a file manager. This blog post has now been updated with details about this finding.

UPDATE 2022-11-09

Lenny Hansson has released IDS signatures that detect BackConnect traffic. More details further down in this blog post.

UPDATE 2022-12-05

Lenny has updated his IDS signatures to alert on BackConnect C2 traffic from port 443 in addition to 8080. The signatures in this blog post have now been updated to Lenny's new rev:2 signatures.

UPDATE 2023-04-14

Brad Duncan made the following suggestion in a toot yesterday:

If the protocol for this VNC traffic from Qakbot looks the same as the BackConnect traffic from IcedID infections, perhaps we can just call it BackConnect Protocol without specifying "IcedID"

This is an excellent idea, since IcedID, QakBot as well as Bazar have all been seen using the same BackConnect protocol. We will therefore refer to the protocol described in this blog post as just the “BackConnect Protocol” from now on. This blog post has also been updated accordingly.

UPDATE 2023-10-02

The release of NetworkMiner 2.8.1 adds a BackConnect protocol parser to NetworkMiner.

IcedID BackConnect C2 Packet Structure

The BackConnect (BC) module uses a proprietary command-and-control (C2) protocol that is pretty straight forward. Both client (bot) and the C2 server typically send commands and responses as 13 byte packets using the following structure:

• Auth: 4 bytes
• Command: 1 byte
• Params: 4 bytes
• ID: 4 bytes

Auth Field

The "Auth" field is presumably used by the bot and C2 server to verify that the other party is communicating using the same protocol and version.

As mentioned by Group-IB and xors the Auth field is typically 0x974F014A (little endian), but we prefer to use the network byte order representation "4a 01 4f 97".

In their IcedID blog post from 2020 Group-IB say:

the auth field that has not changed since at least version 5 of the IcedID core is the constant 0x974F014A

Nevertheless, we recently noticed another BackConnect Auth field being used in the wild. But more on that later.

Commands

The following list of BackConnect C2 commands has been compiled by combining those mentioned by Group-IB with our own analysis of the BackConnect protocol:

• 0x00 = Bot queries for a task
• 0x01 = Set sleep timer
• 0x02 = Bot error
• 0x03 = Reconnect
• 0x04 = Start SOCKS
• 0x05 = Start VNC

We've also discovered these additional commands in BackConnect C2 traffic that uses the Auth value "1f 8b 08 08":

• 0x11 = Start VNC
• 0x12 = Start file manager
• 0x13 = Start reverse shell

Commands 0x04, 0x05, 0x11, 0x12 and 0x13 all cause the bot to connect back to the C2 server using a new BackConnect session, which will be used to wrap either SOCKS, VNC, file manager or reverse shell traffic.

Command 0x01: Set Sleep Timer

The set sleep timer command is issued by the C2 server to instruct the bot to sleep for a certain amount of time before requesting a new task from the C2 server again. The sleep time is defined in the four bytes following directly after the 0x01 command. This value is a 32-bit little endian value indicating the number of seconds the bot should sleep, i.e. "3c 00 00 00" = 0x0000003c = 60 seconds. The most common sleep value seems to be 60 seconds, which is why you'll often see byte sequences like this in IcedID C2 sessions:

zz zz zz zz 01 3c 00 00 00 xx xx xx xx

The following Wireshark display filter will show BackConnect C2 packets, where the bot is configured to sleep for 60 seconds before querying the C2 server for a new command:

tcp.len == 13 and tcp.payload[4:5] == 01:3c:00:00:00

Command 0x04: Start SOCKS

The SOCKS command (0x04) instructs the bot to start the SOCKS module. As an example, the following byte sequence was sent by the IcedID C2 server 91.238.50.80:8080 in Brad Duncan's 2022-06-28 TA578 IcedID pcap on malware-traffic-analysis.net (see frame #10231):

4a 01 4f 97 04 09 00 00 00 8c a2 b1 09

The first four bytes are the auth value, followed by the Start SOCKS command (04).

After receiving this command the bot established a new TCP connection back to the C2 server, where it echoed back the server's "Start SOCKS" command and then started acting like a SOCKS server.

Except for initially echoing the BackConnect Start SOCKS command the SOCKS module actually seems to be compliant with RFC1928, which defines the SOCKS5 protocol. This means that the C2 server can supply an IP address and port number to the bot's SOCKS proxy in order to relay a connection to that host through the bot.

Image: C2 server instructs bot to relay a connection to 188.40.30.100:80

After receiving a Start SOCKS command an IcedID bot immediately establishes a new TCP connection to the specified IP and port, and relays the application layer data back to the C2 server through the SOCKS connection.

Image: Update check of Advanced Port Scanner relayed through the infected machine

In the 2022-06-28 TA578 IcedID pcap the attacker used multiple SOCKS connections to scan the 10.6.21.0/24 network for services running on TCP ports 21, 80, 445 and 4899. That last port (TCP 4899) is typically used by Radmin VPN, which just so happens to be created by the outfit "Famatech" who also develop the "Advanced Port Scanner". The attacker also used the SOCKS module to make several HTTPS connections to servers like 18.204.62.252 (tlx.3lift[.]com), 23.94.138.115 (cmd5[.]org) and 74.119.118.137 (cat.da.us.criteo[.]com). The attacker also proxied connections to 40.97.120.242 and 52.96.182.162 (outlook.live.com) through the infected bot.

NetworkMiner showing hosts that the bot proxied TLS traffic to

JA3 Fingerprints from Proxied Traffic

Since the SOCKS proxy doesn't touch the application layer data we know that the client TLS handshake packets are coming from the C2 server rather than from the bot that's running the SOCKS proxy. This means that we can fingerprint the actual TLS client using JA3.

As you can see in the CapLoader screenshot above, most proxied TLS sessions use the cd08e31494f9531f560d64c695473da9 JA3 hash, but two of them use the rare JA3 hash 598872011444709307b861ae817a4b60. That rare JA3 hash was used only when connecting to outlook.live.com.

Command 0x05 or 0x11: VNC

Brad Duncan's 2022-06-28 TA578 IcedID pcap also contains the "Start VNC" command 0x05.

Image: Flow transcript of Start VNC command

As can be seen in the CapLoader screenshot above, Start VNC commands were sent at 16:33:33 and 16:34:06 UTC. And just like the SOCKS command, this caused the bot to establish a new connection back to the C2 server, echo the "Start VNC" command and then proceed with the VNC traffic.

Image: Flow transcript of IcedID VNC traffic in ASCII encoding

Command 0x13: Reverse Shell

Brad posted a new capture file with network traffic from another IcedID infection last week (2022-10-04). He also noted that the traffic to 51.89.201.236:8080 was different from normal IcedID post-infection traffic.

After looking at this C2 traffic I discovered that it was in fact using the IcedID BackConnect protocol outlined in this blog post, but the Auth field "4a 01 4f 97" had been replaced with "1f 8b 08 08".

That exact byte sequence is a common file header for gzip compressed files (RFC1952), where

• 1f 8b = GZIP magic
• 08 = DEFLATE compression
• 08 = Original file name header present

IcedID has previously been seen using fake gzip file headers in payloads, but this time even the C2 packets include the gzip header!

Image: Transcript of TCP session to 51.89.201.236:8080

The C2 traffic also contained the command 0x13, which I hadn't seen before. Just like the SOCKS and VNC commands, this one triggered the bot to establish a new connection back to the C2 server. But the bot sent a task query command (00) this time, instead of echoing the C2 server's command (0x13). The new TCP session then transitioned into what looks like a reverse shell session.

Image: Transcript of reverse shell traffic from IcedID BackConnect session

The reverse shell traffic reveals that the attackers retrieved a list of domain admin users and then executed a PowerShell script from aicsoftware[.]com. This PowerShell script was used to install CobaltStrike beacon on the victim's PC.

Command 0x12: File Manager

We discovered the file manager command after this blog post was published. This section has therefore been added after the original publication of this blog post.

The following Wireshark display filter can be used to find file manager commands (0x12) in BackConnect C2 traffic that uses the "1f 8b 08 08" auth value:

tcp.len == 13 and tcp.payload[0:5] == 1f:8b:08:08:12

Image: File manager commands in BackConnect C2

The screenshot above shows that the file manager command was issued three times in 2022-10-31-IcedID-with-DarkVNC-and-Cobalt-Strike-full-pcap-raw.pcap.

Image: BackConnect TCP sessions in CapLoader's Flows view

As you can see in the two screenshots above, each time a file manager command was issued in the C2 session (Wireshark screenshot) the bot established a new TCP connection back to the C2 server (CapLoader screenshot).

The file manager sessions use a proprietary protocol to perform tasks such as listing disks, changing directory and uploading files.

We've identified the following file manager commands:

• DISK = List drives
• CDDIR <path> = Change directory
• PWD = Show current directory
• DIR = List current directory
• PUT <path> = Upload file

IDS Signatures

Lenny Hansson has released IDS signatures that can detect IcedID (and QakBot) BackConnect traffic. I'd like to highlight four of Lenny's signatures here.

Alert on "sleep 60 seconds" C2 command, regardless of Auth value:

alert tcp $EXTERNAL_NET [443,8080] -> $HOME_NET 1024: (msg:"NF - Malware IcedID BackConnect - Wait Command"; flow:established; flags:AP; dsize:13; content:"|01 3c 00 00 00|"; offset:4; depth:5; reference:url,networkforensic.dk; metadata:02112022; classtype:trojan-activity; sid:5006006; rev:3;)

Alert on "start VNC" C2 command with "4a 01 4f 97" Auth:

alert tcp $EXTERNAL_NET [443,8080] -> $HOME_NET 1024: (msg:"NF - Malware IcedID BackConnect - Start VNC command"; flow:established; flags:AP; dsize:13; content:"|4a 01 4f 97 05|"; offset:0; depth:5; reference:url,networkforensic.dk; metadata:03112022; classtype:trojan-activity; sid:5006007; rev:2;)

Alert on "start VNC" C2 command with "1f 8b 08 08" Auth:

alert tcp $EXTERNAL_NET [443,8080] -> $HOME_NET 1024: (msg:"NF - Malware IcedID BackConnect - Start VNC command - 11"; flow:established; flags:AP; dsize:13; content:"|1f 8b 08 08 11|"; offset:0; depth:5; reference:url,networkforensic.dk; metadata:03112022; classtype:trojan-activity; sid:5006011; rev:2;)

Alert on "start file manager" C2 command with "1f 8b 08 08" Auth:

alert tcp $EXTERNAL_NET [443,8080] -> $HOME_NET 1024: (msg:"NF - Malware IcedID BackConnect - Start file manager command"; flow:established; flags:AP; dsize:13; content:"|1f 8b 08 08 12|"; offset:0; depth:5; reference:url,networkforensic.dk; metadata:03112022; classtype:trojan-activity; sid:5006008; rev:2;)

A zip file containing Lenny's Snort rules can be downloaded from networkforensic.dk.

Questions and Answers

Allright, that's all I had to say about the IcedID BackConnect C2 protocol. I'm now ready to take your questions.

Q: Is IcedID's BackConnect VNC traffic the same thing as DarkVNC?

No, DarkVNC traffic doesn't use the BackConnect C2 Packet Structure described in this blog post. Also, one characteristic behavior DarkVNC is that the first C2 packet contains a string that looks like one of these:

• (COMPUTERNAME)_ADDITIONAL_ID-DARKVNC
• BOT-COMPUTERNAME(USERNAME)_ID-REFnnn
• USR-COMPUTERNAME(USERNAME)_ID-REFnnn

Q: Is IcedID's BackConnect VNC traffic the same thing as hVNC?

Almost. hVNC means "hidden VNC" and includes any type of malicious VNC server running on a victim's PC, including IcedID's VNC module as well as DarkVNC.

Q: How did you get Wireshark to decode the SOCKS traffic from IcedID BackConnect?

1. Open the pcap file from 2022-06-28 TA578 IcedID
2. Apply display filter: tcp.port eq 8080
3. Right-click, Decode As, TCP port 8080 = SOCKS
4. Display filter: tcp.dstport eq 8080 and tcp.len eq 13 and tcp.payload[0:5] eq 4a:01:4f:97:04
5. Select all packets (Ctrl+A)
6. Edit, Ignore Packets (Ctrl+D)
7. Display filter: socks.dst

Q: Can CapLoader's Protocol Identification feature detect the BackConnect protocol?

The version used in this blog post (1.9.4) doesn't have a protocol model for the BackConnect protocol, but later versions can identify IcedID's BackConnect protocol regardless of port. CapLoader version 1.9.5 (and later) also alerts on BackConnect traffic.

Posted by Erik Hjelmvik on Wednesday, 12 October 2022 18:24:00 (UTC/GMT)

Tags: #IcedID​ #QakBot​ #QBot​ #TA578​ #BackConnect​ #SOCKS​ #SOCKS5​ #VNC​ #JA3​ #gzip​ #PowerShell​

Hunting for C2 Traffic

In this video I look for C2 traffic by doing something I call Rinse-Repeat Threat Hunting, which is a method for removing "normal" traffic in order to look closer at what isn't normal.

The video was recorded in a Windows Sandbox in order to avoid accidentally infecting my Windows PC with malware.

The PCAP files analyzed in the video are:

• 2022-06-27-part-1-of-2-Qakbot-with-Cobalt-Strike-and-DarkVNC.pcap
• 2022-06-27-part-2-of-2-Qakbot-with-DarkVNC-and-email-banner-traffic.pcap
• 2022-06-28-TA578-IcedID-with-Cobalt-Strike-raw.pcap

Thank you for sharing these capture files Brad!

IOC List

• QBot source: 23.29.125.210
• QBot md5: 2b55988c0d236edd5ea1a631ccd37b76
• QBot sha1: 033a22c3bb2b0dd1677973e1ae6280e5466e771c
• QBot sha256: 2d68755335776e3de28fcd1757b7dcc07688b31c37205ce2324d92c2f419c6f0
• Qbot proxy protocol server: 23.111.114.52:65400
• QBot C2: 45.46.53.140:2222
• QBot C2 JA3: 51c64c77e60f3980eea90869b68c58a8
• QBot C2 JA3S : 7c02dbae662670040c7af9bd15fb7e2f
• QBot X.509 domain: thdoot.info
• QBot X.509 thumbprint: 5a8ee4be30bd5da709385940a1a6e386e66c20b6
• IcedID BackConnect server: 78.31.67.7:443
• IcedID BackConnect server: 91.238.50.80:8080

References and Links

• herALook.dat (MalwareBazaar)
• herALook.dat (VirusTotal)
• Qbot proxy protocol details (Securelist)
• QBot JA3 hash (DFIR Report)
• IcedID BackConnect protocol (Group-IB)

Update 2022-10-13

Part two of this analysis has been published: IcedID BackConnect Protocol

Posted by Erik Hjelmvik on Friday, 30 September 2022 12:37:00 (UTC/GMT)

Tags: #Threat Hunting​ #PCAP​ #CapLoader​ #NetworkMiner​ #NetworkMiner Professional​ #Video​ #QBot​ #QakBot​ #51c64c77e60f3980eea90869b68c58a8​ #IcedID​ #TA578​

Analysing a malware PCAP with IcedID and Cobalt Strike traffic

This network forensics walkthrough is based on two pcap files released by Brad Duncan on malware-traffic-analysis.net. The traffic was generated by executing a malicious JS file called StolenImages_Evidence.js in a sandbox environment.

The capture file starts with a DNS lookup for banusdona.top, which resolved to 172.67.188.12, followed by an HTTP GET request for "/222g100/index.php" on that domain. The following PowerShell oneliner is returned in the HTTP response from banusdona.top:

This oneliner instructs the initial dropper to download a Win32 DLL payload from http://banusdona[.]top/222g100/main.php and save it as "JwWdx.dat" in the user's temp directory and then run the DLL with:

As you can see in the screenshot below, the HTTP response for this second request to banusdona.top has Content-Type "application/octet-stream", but also a conflicting Content-disposition header of "attachment;filename=data.jpg", which indicates that the file should be saved to disk as "data.jpg". Nevertheless, the "MZ" header in the transferred data reveals that the downloaded data wasn't an image, but a Windows binary (dll or exe).

The downloaded file gets extracted from the pcap file by NetworkMiner as "data.jpg.octet-stream".

Right-clicking "data.jpg.octet-stream" in NetworkMiner and selecting "Calculate MD5..." brings up a new window with additional file details, such as MD5 and SHA hashes of the reassembled file.

This file is available on VirusTotal, where we can see that it's a DLL that several AV vendors identify as "Cerbu" or "IcedID". VirusTotal's C2AE sandbox analysis of the DLL also reveals the domain name "momenturede.fun" in the process' memory. As you might expect, a connection is made to that domain just a few seconds later. A nice overview of these connections can be seen in CapLoader's Flow tab.

The momenturede.fun server returns a 500kB file, which NetworkMiner extracts from the pcap file as "index.gzip".

This turns out to be an encrypted IcedID DLL file, which has been analyzed by Ali Aqeel here:
https://aaqeel01.wordpress.com/2021/04/09/icedid-analysis/

Right after the IcedID download we see a series of HTTPS connections towards odd domains like vaccnavalcod.website, mazzappa.fun, ameripermanentno.website and odichaly.space, all of which resolved to IP 83.97.20.176. That host is most likely a command-and-control (C2) server used by the IcedID malware.

CapLoader's "Services" tab also reveals that the TLS connections to port 443 on 83.97.20.176 are very periodic, with a new connection every 5 minutes. Periodic connection patterns like this is a typical indicator of C2 traffic, where the malware agent connects back to the C2 server on regular intervals to check for new tasks.

The traffic to 83.97.20.176 is encrypted, so we can't inspect the payload to verify whether or not it is IcedID C2 communications. What we can do, however, is to extract the HTTPS server's X.509 certificate and the JA3 hash of the client's TLS implementation from the encrypted traffic.

NetworkMiner has extracted the X.509 certificates for vaccnavalcod.website, mazzappa.fun, ameripermanentno.website and odichaly.space to disk as "localhost.cer".

It turns out that all these sites used the same self-signed certificate, which had SHA1 fingerprint 452e969c51882628dac65e38aff0f8e5ebee6e6b. The X.509 certificate was created using OpenSSL's default values, such as "Internet Widgits Pty Ltd" etc. Further details about this certificate can be found on censys.io.

The JA3 hashes used by the IcedID malware agent can be found in NetworkMiner's Hosts tab as well as in the Parameters tab.

The JA3 hashes for the client that connects to the C2 server are a0e9f5d64349fb13191bc781f81f42e1 and 3b5074b1b5d032e5620f69f9f700ff0e. Several legitimate Windows applications unfortunately have the same JA3 hashes, so we can't use them to uniquely identify the IcedID agents.

The IcedID C2 traffic continues for over 19 hours, at which point we suddenly see a connection to a new suspicious domain called "lesti.net" on 185.141.26.140. The first HTTP request to that domain is used to download a 261703 byte file, as can be seen in this Flow Transcript from CapLoader:

NetworkMiner extracts this file as "9r8z.octet-stream". This turns out to be a Cobalt Strike beacon download, which we can decode with Didier Stevens' fantastic 1768.py script.

The output from 1768.py reveals that this Cobalt Strike beacon is using the following URIs for C2 communication:

• GET URI: http://lesti[.]net/userid=
• POST URI: http://lesti[.]net/update.php

We can also see that the Cobalt Strike license-id (a.k.a. watermark) is 1580103814. This ID can be used to link this Cobalt Strike beacon to other campaigns. Below is a list of Cobalt Strike C2 servers using license-id 1580103814 discovered by Tek in December 2020:

• 45.147.229[.]157
• selfspin[.]com
• savann[.]org
• palside[.]com
• server3.msadwindows[.]com
• mapizzamates[.]com
• fixval[.]com
• rackspare-technology[.]download
• 108.177.235[.]148
• matesmapizza[.]com

Update 4 May 2021

Sergiu Sechel published a blog post yesterday, which included a list of Cobalt Strike C2 servers. We fed this list to Tek's scan_list.py script in order to see if license-id 1580103814 is still active. It turned out it was. We found the following 27 domains and IP's running Cobalt Strike C2 servers on TCP 443 using that license-id.

• 151.236.14[.]53
• 151.236.14[.]53
• 172.241.27[.]70
• 193.29.13[.]201
• 193.29.13[.]201
• 193.29.13[.]209
• 194.165.16[.]60
• 193.29.13[.]209
• 193.29.13[.]201
• 194.165.16[.]60
• 194.165.16[.]60
• dain22[.]net
• drellio[.]com
• feusa[.]net
• fut1[.]net
• helle1[.]net
• hars2t[.]com
• kasaa[.]net
• idxup[.]com
• maren2[.]com
• mgfee[.]com
• massflip[.]com
• oaelf[.]com
• repdot[.]com
• scalewa[.]com
• tulls[.]net
• wellser[.]org

The full output from our re-scan of Sergiu's C2 list can be found on pastebin.

Update 8 May 2021

Security researcher Michael Koczwara is tracking Cobalt Strike license 1580103814 as APT actor LuckyMouse (a.k.a. Emissary Panda or APT 27). Michael's Cobalt Stike C2 dataset, which currently contains 25 unique C2 IPs and domains for license-id 1580103814, is available as a Google Docs spreadsheet (see the "LuckyMouse Actor" tab).

Indicators of Compromise - IOCs

• MD5: 8da75e1f974d1011c91ed3110a4ded38
• SHA1: e9b5e549363fa9fcb362b606b75d131dec6c020e
• SHA256: 0314b8cd45b636f38d07032dc8ed463295710460ea7a4e214c1de7b0e817aab6
• DNS: banusdona.top
• IP: 172.67.188.12
• MD5: f98711dfeeab9c8b4975b2f9a88d8fea
• SHA1: c2bdc885083696b877ab6f0e05a9d968fd7cc2bb
• SHA256: 213e9c8bf7f6d0113193f785cb407f0e8900ba75b9131475796445c11f3ff37c
• DNS: momenturede.fun
• IP: 104.236.115.181
• MD5: 96a535122aba4240e2c6370d0c9a09d3
• SHA1: 485ba347cf898e34a7455e0fd36b0bcf8b03ffd8
• MD5: 11965662e146d97d3fa3288e119aefb2
• SHA1: b63d7ad26df026f6cca07eae14bb10a0ddb77f41
• SHA256: d45b3f9d93171c29a51f9c8011cd61aa44fcb474d59a0b68181bb690dbbf2ef5
• DNS: vaccnavalcod.website
• DNS: mazzappa.fun
• DNS: ameripermanentno.website
• DNS: odichaly.space
• IP: 83.97.20.176
• SHA1: 452e969c51882628dac65e38aff0f8e5ebee6e6b
• DNS: lesti.net
• IP: 185.141.26.140
• MD5: 449c1967d1708d7056053bedb9e45781
• SHA1: 1ab39f1c8fb3f2af47b877cafda4ee09374d7bd3
• SHA256: c7da494880130cdb52bd75dae1556a78f2298a8cc9a2e75ece8a57ca290880d3
• Cobalt Strike Watermark: 1580103814

Network Forensics Training

Are you interested in learning more about how to analyze captured network traffic from malware and hackers? Have a look at our network forensic trainings. Our next class is a live online event called PCAP in the Morning.

Posted by Erik Hjelmvik on Monday, 19 April 2021 09:45:00 (UTC/GMT)

Tags: #Cobalt Strike​ #CobaltStrike​ #IcedID​ #NetworkMiner​ #CapLoader​ #Network Forensics​ #JA3​ #X.509​ #1768.py​ #a0e9f5d64349fb13191bc781f81f42e1​