Cobalt Strike: Decrypting DNS Traffic – Part 5

Cobalt Strike beacons can communicate over DNS. We show how to decode and decrypt DNS traffic in this blog post. This series of blog posts describes different methods to decrypt Cobalt Strike traffic. In part 1 of this series, we revealed private encryption keys found in rogue Cobalt Strike packages. In part 2, we decrypted … Continue reading Cobalt Strike: Decrypting DNS Traffic – Part 5

Cobalt Strike: Decrypting Obfuscated Traffic – Part 4

Encrypted Cobalt Strike C2 traffic can be obfuscated with malleable C2 data transforms. We show how to deobfuscate such traffic. This series of blog posts describes different methods to decrypt Cobalt Strike traffic. In part 1 of this series, we revealed private encryption keys found in rogue Cobalt Strike packages. In part 2, we decrypted … Continue reading Cobalt Strike: Decrypting Obfuscated Traffic – Part 4

Cobalt Strike: Using Process Memory To Decrypt Traffic – Part 3

We decrypt Cobalt Strike traffic with cryptographic keys extracted from process memory. This series of blog posts describes different methods to decrypt Cobalt Strike traffic. In part 1 of this series, we revealed private encryption keys found in rogue Cobalt Strike packages. And in part 2, we decrypted Cobalt Strike traffic starting with a private … Continue reading Cobalt Strike: Using Process Memory To Decrypt Traffic – Part 3

Cobalt Strike: Using Known Private Keys To Decrypt Traffic – Part 2

We decrypt Cobalt Strike traffic using one of 6 private keys we found. In this blog post, we will analyze a Cobalt Strike infection by looking at a full packet capture that was taken during the infection. This analysis includes decryption of the C2 traffic. If you haven't already, we invite you to read part … Continue reading Cobalt Strike: Using Known Private Keys To Decrypt Traffic – Part 2

Cobalt Strike: Using Known Private Keys To Decrypt Traffic – Part 1

We found 6 private keys for rogue Cobalt Strike software, enabling C2 network traffic decryption. The communication between a Cobalt Strike beacon (client) and a Cobalt Strike team server (C2) is encrypted with AES (even when it takes place over HTTPS). The AES key is generated by the beacon, and communicated to the C2 using … Continue reading Cobalt Strike: Using Known Private Keys To Decrypt Traffic – Part 1

Credential harvesting and automated validation: a case study

During our incident response engagements, we very frequently come across phishing lures set up to harvest as many credentials as possible, which will likely be sold afterwards or used in follow-up attacks against an organization (or both). While many of these credential harvesting attacks follow the same pattern, from time to time we stumble upon … Continue reading Credential harvesting and automated validation: a case study

Detecting the sudden appearance of events with ee-outliers and Elasticsearch

Recently, for our open-sourced ee-outliers framework, we released a new outlier model capable of detecting the sudden appearance of one or multiple field values of an Elasticsearch event. For example, this model could spot new TLDs that are suddenly being contacted (DNS/SSL) and communicating with C2 domains. It could also detect an executable that suddenly … Continue reading Detecting the sudden appearance of events with ee-outliers and Elasticsearch

OpenSSH User Enumeration Vulnerability: a Close Look

Intro An OpenSSH user enumeration vulnerability (CVE-2018-15473) became public via a GitHub commit. This vulnerability does not produce a list of valid usernames, but it does allow guessing of usernames. In this blog post, we take a closer look at this vulnerability and propose mitigation and monitoring actions. Technical details This vulnerability manifests itself in … Continue reading OpenSSH User Enumeration Vulnerability: a Close Look

Shortcomings of blacklisting in Adobe Reader and what you can do about it

A variation of a class of malicious PDFs appeared in the wild. In this blog post, we will show you how to protect your systems and how to analyze these PDFs. The PDFs embed a file type with extension .SettingContent-ms that can be used on Windows 10 to execute arbitrary code. We have observed on … Continue reading Shortcomings of blacklisting in Adobe Reader and what you can do about it