Showing blog posts from February 2018


Examining Malware Redirects with NetworkMiner Professional

This network forensics video tutorial covers analysis of a malware redirect chain, where a PC is infected through the RIG Exploit Kit. A PCAP file, from Brad Duncan's malware-traffic-analysis.net website, is opened in NetworkMiner Professional in order to follow a redirect chain via a couple of hacked websites before delivering malware to the PC.

Resources
https://www.malware-traffic-analysis.net/2014/11/16/index.html
Meadgive on VirusTotal
CVE-2014-0569 Flash Exploit on VirusTotal
CVE-2012-0507 Java Exploit on VirusTotal
NetworkMiner Professional

IOCs
www.ciniholland.nl
24corp-shop.com
stand.trustandprobaterealty.com
793b698a82d999f1eb75525d050ebe16
f8482f5c4632fe237d062451b42393498a8d628ed9dee27147251f484e837a42
7b3baa7d6bb3720f369219789e38d6ab
e2e33b802a0d939d07bd8291f23484c2f68ccc33dc0655eb4493e5d3aebc0747
1e34fdebbf655cebea78b45e43520ddf
178be0ed83a7a9020121dee1c305fd6ca3b74d15836835cfb1684da0b44190d3

Check out our series of network forensic video tutorials for more tips and tricks on how to analyze captured network traffic.

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Posted by Erik Hjelmvik on Monday, 26 February 2018 11:19:00 (UTC/GMT)


Analyzing Kelihos SPAM in CapLoader and NetworkMiner

This network forensics video tutorial covers how to analyze SPAM email traffic from the Kelihos botnet. The analyzed PCAP file comes from the Stratosphere IPS project, where Sebastian Garcia and his colleagues execute malware samples in sandboxes. The particular malware sample execution we are looking at this time is from the CTU-Malware-Capture-Botnet-149-2 dataset.

Resources

IOCs
990e5daa285f5c9c6398811edc68a659
e4f7fa6a0846e4649cc41d116c40f97835d3bb7d3d0391d3540482f077aa4493
6c55 5545 0310 4840

Check out our series of network forensic video tutorials for more tips and tricks on how to analyze captured network traffic.

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Posted by Erik Hjelmvik on Monday, 19 February 2018 06:37:00 (UTC/GMT)


Antivirus Scanning of a PCAP File

This second video in our series of network forensic video tutorials covers a quick and crude way to scan a PCAP file for malware. It's all done locally without having to run the PCAP through an IDS. Kudos to Lenny Hanson for showing me this little trick!

Antivirus Scanning of a PCAP File

Resources

IOCs
178.62.142.240
soquumaihi.co.vu
9fd51fb05cb0ea89185fc1355ebf047cC
8cf7b281a0db4029456e416dbe05d21d17af0cad86f67e054268f5e2c46c43ed
119.238.10.9
96b430041aed13413ec2b5ae91954f39
e79ef634265b9686f90241be0e05940354dc2c2b43d087e09bb846eec34dad35

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Posted by Erik Hjelmvik on Monday, 12 February 2018 08:00:00 (UTC/GMT)


Examining an x509 Covert Channel

Jason Reaves gave a talk titled “Malware C2 over x509 certificate exchange” at BSides Springfield 2017, where he demonstrated that the SSL handshake can be abused by malware as a covert command-and-control (C2) channel.

Jason Reaves presenting at BSides Springfield 2017

He got the idea while analyzing the Vawtrak malware after discovering that it read multiple fields in the X.509 certificate provided by the server before proceeding. Jason initially thought these fields were used as a C2 channel, but then realized that Vawtrak performed a variant of certificate pinning in order to discover SSL man-in-the-middle attempts.

Nevertheless, Jason decided to actually implement a proof-of-concept (PoC) that uses the X.509 certificate as a C2 channel. Jason’s code is now available on GitHub along with a PCAP file demonstrating this covert C2 channel. Of course I couldn’t resist having a little look at this PCAP file in NetworkMiner.

The first thing I noticed was that the proof-of-concept PCAP ran the SSL session on TCP 4433, which prevented NetworkMiner from parsing the traffic as SSL. However, I was able to parse the SSL traffic with NetworkMiner Professional just fine thanks to the port-independent-protocol-identification feature (a.k.a Dynamic Port Detection), which made the Pro-version parse TCP 4433 as SSL/TLS.

X.509 certificates extracted from PCAP with NetworkMiner
Image: X.509 certificates extracted from PCAP with NetworkMiner

A “normal” x509 certificate size is usually around 1kB, so certificates that are 11kB should be considered as anomalies. Also, opening one of these .cer files reveals an extremely large value in the Subject Key Identifier field.

X.509 certificate with MZ header in the Subject Key Identifier field

Not only is this field very large, it also starts with the familiar “4D 5A” MZ header sequence.

NetworkMiner additionally parses details from the certificates that it extracts from PCAP files, so the Subject Key Identifier field is actually accessible from within NetworkMiner, as shown in the screenshot below.

Parameters tab in NetworkMiner showing X.509 certificate details

You can also see that NetworkMiner validates the certificate using the local trusted root certificates. Not surprisingly, this certificates is not trusted (certificate valid = FALSE). It would be most unlikely that anyone would manage to include arbitrary data like this in a signed certificate.


Extracting the MZ Binary from the Covert X.509 Channel

Even though NetworkMiner excels at pulling out files from PCAPs, this is definitively an occasion where manual handling is required. Jason’s PoC implementation actually uses a whopping 79 individual certificates in order to transfer this Mimikatz binary, which is 785 kB.

Here’s a tshark oneliner you can use to extract the Mimicatz binary from Jason's example PCAP file.

tshark -r mimikatz_sent.pcap -Y 'ssl.handshake.certificate_length gt 2000' -T fields -e x509ce.SubjectKeyIdentifier -d tcp.port==4433,ssl | tr -d ':\n' | xxd -r -p > mimikatz.exe

Detecting x509 Anomalies

Even though covert channels using x509 certificates isn’t a “thing” (yet?) it’s still a good idea to think about how this type of covert signaling can be detected. Just looking for large Subject Key Identifier fields is probably too specific, since there are other fields and extensions in X.509 that could also be used to transmit data. A better approach would be to alert on certificates larger than, let’s say, 3kB. Multiple certificates can also be chained together in a single TLS handshake certificate record, so it would also make sense to look for handshake records larger than 8kB (rough estimate).

Bro IDS logo

This type of anomaly-centric intrusion detection is typically best done using the Bro IDS, which provides easy programmatic access to the X.509 certificate and SSL handshake.

There will be false positives when alerting on large certificates in this manner, which is why I recommend to also check if the certificates have been signed by a trusted root or not. A certificate that is signed by a trusted root is very unlikely to contain malicious data.

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Posted by Erik Hjelmvik on Tuesday, 06 February 2018 12:13:00 (UTC/GMT)


Zyklon Malware Network Forensics Video Tutorial

We are releasing a series of network forensics video tutorials throughout the next few weeks. First up is this analysis of a PCAP file containing network traffic from the "Zyklon H.T.T.P." malware.

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

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

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book

Recommended Books

» The Practice of Network Security Monitoring, Richard Bejtlich (2013)

» Applied Network Security Monitoring, Chris Sanders and Jason Smith (2013)

» Network Forensics, Sherri Davidoff and Jonathan Ham (2012)

» The Tao of Network Security Monitoring, Richard Bejtlich (2004)

» Practical Packet Analysis, Chris Sanders (2017)

» Windows Forensic Analysis, Harlan Carvey (2009)

» TCP/IP Illustrated, Volume 1, Kevin Fall and Richard Stevens (2011)

» Industrial Network Security, Eric D. Knapp and Joel Langill (2014)