Introduction

Today's diary is a forensic contest for May 2021 based on a packet capture (pcap) with Windows-based infection traffic.  Like last month, this month's prize is a Raspberry Pi.  Rules for the contest follow:

• Only one submission per person.
• The first person to submit the correct answers will win the Raspberry Pi.
• Submissions will be made using the form on our contact page at: https://isc.sans.edu/contact.html
• Use May 2021 Forensic Contest for the Subject: line.
• Provide the following information:
  • IP address of the infected Windows computer.
  • Host name of the infected Windows computer.
  • User account name on the infected Windows computer.
  • Date and time the infection activity began in UTC (the GMT or Zulu timezone).
  • The family of malware involved.

Material for our May 2021 forensic contest is located at this Github repository.  The repository contains a zip archive with a pcap of network traffic from the infected Windows host.  I always recommend people review pcaps of malware in a non-Windows environment, if possible.

The source of this infection was a malicious email.  Fortunately, an email provider's spam filters usually catch the vast majority of malware before it hits someone's inbox.  Unfortunately, due to the vast amount of spam, some malicious emails make it through to their intended victims.

Shown above:  A visual representation of email spam filtering on a daily basis.

Requirements

Analysis of the infection traffic requires Wireshark or some other pcap analysis tool.  Wireshark is my tool of choice to review pcaps of infection traffic.  However, default settings for Wireshark are not optimized for web-based malware traffic.  That's why I encourage people to customize Wireshark after installing it.  To help, I've written a series of tutorials.  The ones most helpful for this quiz are:

• Wireshark Tutorial: Changing Your Column Display
• Wireshark Tutorial: Identifying Hosts and Users
• Wireshark Tutorial: Display Filter Expressions
• Using Wireshark - Exporting Objects from a Pcap

I always recommend participants review these pcaps in a non-Windows environment like BSD, Linux, or macOS.  Why?  Because this pcap contains traffic with Windows-based malware.  If you're using a Windows host to review such pcaps, your antivirus (or Windows Defender) may delete or alter the pcap.  Worst case?  If you extract malware from a pcap and accidentally run it, you might infect your Windows computer.

Active Directory (AD) Environment

The infected Windows host is part of an AD environment, so the pcap contains information about the Windows user account. The user account is formatted as firstname.lastname.  The AD environment characteristics are:

• LAN segment range: 172.17.4.0/24 (172.17.4.0 through 172.17.4.255)
• Domain: nutmeg-station.com
• Domain Controller: 172.17.4.4 - NutmegCrazy-DC
• LAN segment gateway: 172.17.4.1
• LAN segment broadcast address: 172.17.4.255

Final Words

Again, the zip archive with a pcap of the infection traffic is available in this Github repository.  The winner of today's contest and analysis of the infection traffic will be posted in an upcoming ISC diary two weeks from today on Wednesday May 19th.

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Brad Duncan
brad [at] malware-traffic-analysis.net