NETRESEC Network Security Blog - Tag : NetBIOS

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Robust Indicators of Compromise for SUNBURST

Were you targeted by SUNBURST? Image credit: NASA

There has been a great deal of confusion regarding what network based Indicators of Compromise (IOC) SolarWinds Orion customers can use to self assess whether or not they have been targeted after having installed a software update with the SUNBURST backdoor. Many of the published IOCs only indicate that a backdoored SolarWinds Orion update has been installed, but the question that many security teams are trying to answer is whether or not the installed backdoor has been been used by the threat actor.

Dont trust everything you read!

There is a widespread misunderstanding that receiving a so-called “NetBios” DNS A record (for example an address in 8.18.144.0/23) in response to a *.avsvmcloud.com DNS query would mean that you’ve been targeted. Our analysis of the decompiled SUNBURST code and passive DNS data show that that receiving a “NetBios” response does not necessarily mean that the client has been targeted. Unfortunately this misunderstanding has lead to various sensationalist stories being published with long lists of companies and organizations that are claimed to be “singled out by the hacking group for the second stage of the attack”, “explicitly selected by the SolarWinds hackers for further activities” or “breached via SolarWinds and then specifically targeted by the hackers for additional internal compromise”.

Another common misunderstanding is that clients sending *.avsvmcloud.com DNS queries with encoded timestamps, and optionally a list of installed/running AV products, have been actively targeted. Our analysis of the decompiled SUNBURST code show that the timestamped “Pings” or AV service status reports get exfiltrated in DNS traffic after the client’s internal AD domain has been sent, but before the perpetrators decide whether or not they want to activate the backdoor.

Indicators of a Targeted Attack

So what network based IOC’s can incident responders, blue teams and SOC analysts use in order to see if they have been targeted by the SUNBURST operators?

The following network based events indicate that a client has been actively targeted and the SUNBURST backdoor has progressed beyond the initial mode of operation:

  • Received a DNS A record for an *.avsvmcloud.com query, that points to an IP address in any of the following three networks: 18.130.0.0/16, 99.79.0.0/16 or 184.72.0.0/15
  • Sent an *.avsvmcloud.com DNS query with the STAGE2 flag encoded in the subdomain.
  • Received a CNAME record for a query to *.avsvmcloud.com
These three indicators are DNS based, so organizations will need to have a full historical backlog of DNS transactions ranging back to April 2020 in order to use them reliably.

Another network based IOC is HTTPS communication to one of the known STAGE3 C2 domains. However, please note that the C2 domain list might not be complete. It is even possible that a unique C2 domain is used for each victim. Nevertheless, here’s a list of the SUNBURST STAGE3 C2 domains we are currently aware of:

  • avsvmcloud[.]com
  • databasegalore[.]com
  • deftsecurity[.]com
  • digitalcollege[.]org
  • freescanonline[.]com
  • globalnetworkissues[.]com
  • highdatabase[.]com
  • incomeupdate[.]com
  • kubecloud[.]com
  • lcomputers[.]com
  • mobilnweb[.]com
  • panhardware[.]com
  • seobundlekit[.]com
  • solartrackingsystem[.]net
  • thedoccloud[.]com
  • virtualwebdata[.]com
  • webcodez[.]com
  • websitetheme[.]com
  • zupertech[.]com

Palo Alto was a Targeted SUNBURST Victim

We can now verify that Palo Alto was among the targeted SUNBURST victims, because their DNS request for "5qbtj04rcbp3tiq8bo6t.appsync.api.us.east.1.avsvmcloud.com" contains an encoded STAGE2 flag. The attack took place on September 29 at around 04:00 UTC, according to the timestamp that was also encoded into the avsvmcloud subdomain.

paloaltonetworks SUNBURST STAGE2 detected by SunburstDomainDecoder

Image: Parsing passive DNS data from Dancho Danchev with SunburstDomainDecoder v1.9 and filtering on GUID “22334A7227544B1E”.

Palo Alto's CEO Nikesh Arora has confirmed that they were hit by SUNBURST (or "SolarStorm" as they call it), but they don’t provide much details. Here’s what Nikesh wrote on December 17:

Recently, we experienced an attempt to download Cobalt Strike on one of our IT SolarWinds servers. [...]

We thought this was an isolated incident, however, on Dec. 13, we became aware that the SolarWinds software supply chain was compromised and it became clear that the incident we prevented was an attempted SolarStorm attack.

Our SUNBURST STAGE2 Victim Table has now been updated to include Palo Alto along side the other targeted victims.

Posted by Erik Hjelmvik on Monday, 11 January 2021 10:30:00 (UTC/GMT)

Tags: #SUNBURST#SolarWinds#SolarStorm#avsvmcloud#STAGE2#DNS#CNAME#avsvmcloud.com#Cobalt Strike#DNS#FireEye

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NetworkMiner 2.5 Released

NetworkMiner 2.5

I am happy to announce the release of NetworkMiner 2.5 today! This new version includes new features like JA3 and parsers for the HTTP/2 and DoH protocols. We have also added support for a few older protocols that are still widely used, such as Kerberos and the CIFS browser protocol. Additionally, NetworkMiner can now parse PCAP files up to twice as fast as before!

Improving Passive TLS Analysis with JA3

Almost all web traffic is TLS encrypted nowadays, which prevents incident responders, analysts and investigators from inspecting otherwise unencrypted HTTP traffic for clues about malicious behavior or criminal intent. This requires analysts to use alternative approaches, such as looking at hostnames and X.509 certificates. This type of analysis is supported by NetworkMiner, since it parses Server Name Indication fields in client TLS handshakes and extracts X.509 certificates automatically when PCAP files are loaded.

In this release we’ve also added support for another passive TLS analysis technique called JA3, which is a method for fingerprinting TLS client implementations.

NetworkMiner leverages the JA3 fingerprint database from Trisul Network Analytics in order to match observed JA3 hashes to hashes of known malware and “normal” applications. This is what it looks like when the capture file “snort.log.1428364808”, from the FIRST 2015 “Hands-on Network Forensics” training (available here), has been loaded into NetworkMiner 2.5:

JA3 fingerprint of a Skype client

Image: JA3 fingerprint of a Skype client in NetworkMiner 2.5

The JA3 hash is also available in the “Parameters” tab, which is useful in order to find out what hosts that particular TLS implementation was reaching out to.

Filtering on JA3 hash 06207a1730b5deeb207b0556e102ded2 in NetworkMiner 2.5

Image: Filtering on JA3 hash 06207a1730b5deeb207b0556e102ded2

HTTP/2 and DoH Support

Passive analysis of TLS traffic, such as HTTPS, often doesn’t give sufficient visibility. Many organizations therefore use TLS proxies in order to decrypt the traffic going in and out from their networks. However, more than half of all HTTPS traffic is actually http2 (RFC 7540) nowadays. This has previously been an issue for users who wanted to analyze decrypted http2 traffic from their TLS intercepting proxies with NetworkMiner. We’re happy to announce that NetworkMiner now can parse http2 traffic, that has been decrypted by a TLS proxy, and extract files from the http2 transfers.

NetworkMiner 2.5 also supports the DNS over HTTPS (DoH) protocol (RFC 8484), which is a technique for sending DNS queries as http2 POST requests and parsing the returned data as DNS responses. We’ve incorporated the DoH data into NetworkMiner’s DNS tab, so that you can analyze it just like normal DNS traffic.

DoH traffic to mozilla.cloudflare-dns.com in NetworkMiner’s DNS tab

Image: DoH traffic to mozilla.cloudflare-dns.com in NetworkMiner’s DNS tab

Please note that NetworkMiner 2.5 does not perform TLS decryption. This means that NetworkMiner can only parse the contents of a TLS stream if it has been decrypted by a TLS proxy, such as PolarProxy.

Extracting Kerberos Hashes from PCAP

NetworkMiner’s support for the Kerberos protocol allows you to passively track which user accounts that are authenticating to what services, simply by monitoring network traffic. This is a feature is essential in order to track credential theft and lateral movement by adversaries inside your networks. After implementing kerberos username and hash extraction we realized that this feature could also be valuable for penetration testers. We therefore decided to present extracted Kerberos credentials in a format that is compatible with tools like hashcat and John the Ripper.

Kerberos krb5pa, krb5asrep and krb5tgs credentials extracted from the Wireshark sample capture file

Image: Kerberos krb5pa, krb5asrep and krb5tgs credentials extracted from the Wireshark sample capture file Krb-contrained-delegation.cap

For more information about Kerberos hashes, please see our Extracting Kerberos Credentials from PCAP blog post.

Even more NetBIOS and CIFS Artifacts!

NetworkMiner is a popular tool for extracting files transferred over SMB and SMB2 from capture files. It can also extract a great deal of information about the communicating hosts from protocols like NetBIOS and SMB/CIFS, but earlier this year Chris Raiter notified us about an important piece of information that was missing in NetworkMiner: NetBIOS Name Service (NBNS) lookups and responses!

Detection and export of NBNS packets request on twitter

A couple of months later Dan Gunter sent us another great feature request for another protocol that runs on top of NetBIOS: the CIFS Browser Protocol (aka MS-BRWS).

We’re happy to announce that NBNS queries and responses are now shown in NetworkMiner’s Parameters tab, and details like hostnames, domain names, Windows versions and uptime us extracted from the MS-BRWS protocol. See the screenshots below, which were created by loading the capture file “case09.pcap” from Richard Bejtlich’s TCP/IP Weapons School 2.0 Sample Lab into NetworkMiner 2.5. Thanks for sharing Richard!

Hostname, domain and Windows version extracted from MS-BRWS traffic

Image: Hostname, domain and Windows version extracted from MS-BRWS traffic

NBNS queries and responses in NetworkMiner’s Parameters tab

Image: NBNS queries and responses in NetworkMiner’s Parameters tab

Mono 5 Required for Linux and MacOS

Linux and MacOS users, who run NetworkMiner with help of Mono, will need to ensure they have Mono 5 (or later) installed in order to run NetworkMiner 2.5. We recommend using at least Mono 5.18.

Instructions for installing NetworkMiner on Linux can be found in our blog post ”HowTo install NetworkMiner in Ubuntu Fedora and Arch Linux”.

MacOS users can refer to our “Running NetworkMiner on Mac OS X” blog post.

Users who are unable to install Mono 5 are recommended to use the old NetworkMiner 2.4 release, which can be downloaded here:
https://www.netresec.com/?download=NetworkMiner_2-4

NetworkMiner Professional

Apart from the features mentioned so far, our commercial tool NetworkMiner Professional now comes with a few additional new features. One of these features is port independent identification of RDP traffic, so that mstshash credentials can be extracted from RDP sessions even if the service doesn’t run on port 3389. The OSINT lookup context menus in NetworkMiner Professional have also been enriched with the following online services:

Several new features have also been included in the command line tool NetworkMinerCLI, including:

  • Recursive loading of PCAP files with the "-R” switch.
  • Configurable export types (hosts, files, DNS etc) with the “-x” switch.
  • Relative paths in CSV, XML and JSON/CASE exports unless the “-- absolutePaths” switch is used.

Credits

I’d like to thank Dan Gunter, Chris Raiter, Chris Sistrunk and a few more (who I cannot mention here) for contributing with feature requests and bug reports that have helped improve NetworkMiner.

Upgrading to Version 2.5

Users who have purchased a license for NetworkMiner Professional 2.x can download a free update to version 2.5 from our customer portal, or use the “Help > Check for Updates” feature. 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 Thursday, 07 November 2019 11:45:00 (UTC/GMT)

Tags: #NetworkMiner#JA3#HTTP/2#http2#DoH#Kerberos#NetBIOS#PCAP#hashcat#John#NetworkMinerCLI#OSINT

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