DNS describes the structure of resources on the internet. It can provide lots of valuable information about (attacker or target) infrastructure. However, in order to query DNS records, you must already know the exact domains or subdomains to query. When examining unknown infrastructure, this is not practical. On top of that, DNS records can change often, so historical information is lost. Passive DNS databases help solve both of these problems. Farsight Security DNSDB is the largest passive DNS database in the world. With DNSDB, you can answer questions like “How has this network infrastructure changed over time?”, “What other domains and subdomain point (or have pointed to) this IP address?”, “What are the subdomains and resource records for this domain?”
Information Security
Posts related to information security, including news, tutorials, malware analysis, and threat intelligence.
An introduction to DNS
The Domain Name System (DNS) is best known as the way domain names are converted into IP addresses that clients connect to, but there are many other uses for DNS. Read on to learn more.
How to examine a credential harvesting page using Microsoft Edge
Recently I analyzed a credential harvesting page with some interesting characteristics that made a great teaching moment. In this post, I’ll go over how I used the developer tools built into Microsoft Edge to examine the credential harvesting page.
How the Parler data was legally acquired by activists
Based on published source code and conversations with the woman behind the Parler dump (donk_enby on Twitter), I can completely explain how the Parler data was acquired, and why it was legal. The story making the rounds on Reddit claiming that she somehow hacked Parler and got admin access is third-hand bad techno-madlibs fiction. What she actually did was reverse-engineer the protocol (API) used by the Parler iOS app to communicate with the website backend.
How to forward a forensic copy of an email as an attachment
If you receive a fraudulent email, can be very useful to send a full forensic copy to an organization that is being spoofed, industry partners, and law enforcement.
When a user clicks forward in a mail client, the client copies the message’s content and attachments to a new message. The original message headers are not included.
In order to send a full forensic sample that includes the original message headers, the original message must be sent as an attachment in a new message. The process for doing this varies by mail client.
How to view email headers
Email headers contain very useful information for tracing a message’s origin and troubleshooting its delivery. Email headers are written with the oldest headers at the bottom, and the newest headers at the top. By reading the headers in the correct order, you can see how the message was passed from one mail server to another, and the actions each mail server took along the way.
Most email clients have a function to display a message’s headers. The exact steps depends on the client. In most cases, this requires the desktop version of the client.
Proofpoint is forcing their customers to pay for Email Fraud Defense to get aggregate DMARC data from their own gateways
I have written extensively about the DMARC email security standard, including publishing a comprehensive guide on how to implement it, with or without additional third party vendors. I also do a little consulting on DMARC deployment best practices. One of those consulting clients uses Proofpoint for their email gateway. They also use Dmarcian, a reasonably priced DMARC report analytics service that also publishes a ton of public content for the good of the community. We were considering moving the client’s DMARC policy from monitor only (p=none) to an enforced state (p=reject) after many hours of steadily improving the SPF and DKIM alignment of their email sources. As I took another look at the aggregate (rua) DMARC data in Dmarcian, I noticed something odd: Dmarcian was getting aggregate reports from all of the expected third party email recipients, like Google, Yahoo, Comcast, and the client’s industry partners, but I didn’t see any reporting from the client’s own Proofpoint gateways.
Emotet malspam campaign exploits reliance on magic for file type detection
Emotet is a Trojan designed to steal banking information. It is frequently spread by sending phishing emails to governments, banks, healthcare organizations, and schools. The phishing emails will often claim to be an invoice, with a malicious Microsoft Word document attached. The email may often appear to be from a trusted supplier. Once the attachment or link is opened, the target is prompted to click “Enable content”, which would allow the dropper to install Emotet.
I recently encountered two Emotet dropper samples (0b9ccb04553ba5f1ce784630ef9b2c478ed13a96e89c65dcd9c94205c235ea12 and eff6619aee017ee5d04c539ff12c63a199a1e489660f7156b95e562667393d3c) that would not run correctly in my malware sandbox. I soon found the cause of the problem: the file type had been detected as a generic XML file, rather than what it really is: a Microsoft Word document.
How to inspect the certificate of a mail server over a CLI
If you ever need to inspect the certificate of a remote SMTP server, you can use the openssl CLI tool.
If you need to check STARTTLS:
openssl s_client -connect mail.example.com:25 -starttls smtp
Or, for a standard secure SMTP port:
openssl s_client -connect mail.example.com:465
To save the certificate to a file, just redirect the output:
openssl s_client -connect mail.example.com:25 -starttls smtp > mail.example.com.crt
You can also check SMTP TLS using MX Toolbox or Check TLS.
Demystifying DMARC: A guide to preventing email spoofing
DMARC can stop spoofed spam and phishing from reaching you and your customers, protecting your information security and your brand. However, complexity and misconceptions deter many organizations from ever deploying it. Part mythbusting , part implementation guide, this post explains the shortcomings of SPF and DKIM, what DMARC is, how to deploy DMARC properly, and how to respond to DMARC reports – all without the need for an additional vendor, thanks to open source software!