NETRESEC Network Security Blog

Identifying malware families is hard. Malware samples are often packed, strings encrypted and configurations may only appear after several stages of execution. Even experienced reverse engineers can get the malware family wrong and commercial sandboxes do not always produce correct classifications.[...]

A few more handy features have been added to PolarProxy, our TLS inspection proxy. PolarProxy can now tunnel outgoing connections through SOCKS proxies and supports environment variables as an alternative to command-line arguments. PolarProxy also ships with a software bill of materials (SBOM), prov[...]

CERT Polska recently published a follow-up report detailing the hack of a Polish combined heat and power (CHP) plant in December 2025. CERT Polskas report concludes with several important recommendations, including protecting OT systems through network segmentation and monitoring traffic entering an[...]

This post describes the binary command-and-control (C2) protocol used by CNCMachineRMS, a recently identified remote access trojan (RAT). We cover how the protocol was discovered, how its infrastructure was identified, and how network defenders can detect it. Background We have been tracking a previ[...]

Please stop classifying malware as zgRAT. That malware label is confusing. As far as I know, there isnt a proper definition of what zgRAT actually is. Some claim that zgRAT is the same malware family as PureLogs, while others argue that zgRAT should be mapped to PureRAT. There is also a blog post by[...]

Fareed Radzi recently blogged about a malware campaign observed earlier in June by Kasperskys GReAT team. The malware campaign embedded malicious code in VBScripts, which were distributed through WhatsApp DMs. The VBScript then dropped the legitimate Remote Monitoring and Management (RMM) tool Manag[...]

Ive been thinking about threat intelligence lately. Specifically: indicators of compromise (IOC), how and where to share them to cause maximum pain to adversaries and help as many organizations as possible protect themselves. I regularly analyze malware traffic from sandboxes such as ANY.RUN, Triage[...]

Our TLS inspection proxy PolarProxy has been updated with bug fixes, improved performance and more reliable PCAP output. The recent PolarProxy 2.0 release added musl/Alpine compatibility and support for unencrypted HTTP proxy requests. But there were a few small, yet very important, updates that unf[...]

CapLoader has been updated to version 2.1.0. The new release comes with better JA3/JA4 extraction and integration of additional threat-intel and OSINT services. We have also added support for more encapsulation protocols. TLS Client Hello Reassembly TLS handshakes no longer reliably fit in a single[...]

A new major release of PolarProxy is out with a self-contained single-file binary, expanded platform support (musl/ARM64), and improved container and service plumbing. PolarProxy is a transparent TLS/SSL inspection proxy built for incident responders, malware analysts and security researchers. It de[...]

There is a wonderful little web-based alert and event front-end called EveBox, which renders Eve JSON formatted data to a web UI. This blog post demonstrates how EveBox can be used to show alert and flow information that FlowCarp has extracted from a Remcos malware infection. Remcos RAT The starting[...]

I am thrilled to announce the release of a brand new tool called FlowCarp! FlowCarp is a simple command line tool that performs a very complicated task. It identifies the application layer protocol in network traffic without relying on port numbers, static signatures or code that tries to parse the[...]

Googles Threat Intelligence Group (GTIG) and Mandiants recent Disrupting the GRIDTIDE Global Cyber Espionage Campaign report is great and it has lots of good Indicators of Compromise (IOC). Many of these IOCs had already been shared by CISA last year as part of their Alert AA25-141A titled Russian G[...]

njRAT is a remote access trojan that has been around for more than 10 years and still remains one of the most popular RATs among criminal threat actors. This blog post demonstrates how NetworkMiner Professional can be used to decode the njRAT C2 traffic to extract artifacts like screenshots, command[...]

This video tutorial demonstrates how malware XOR encrypted and obfuscated C2 traffic can be decoded with CyberChef. The analyzed PCAP files can be downloaded from malware-traffic-analysis.net. CyberChef recipe to decode the reverse shell traffic to 103.27.157.146:4444: From_Hex(Auto) XOR({option:Hex[...]

This blog post demonstrates how artifacts, such as reverse shell commands and VNC session screenshots, can be extracted from Latrodectus BackConnect C2 traffic with NetworkMiner. I recently learned that the great folks from The DFIR Report have done a writeup covering the Latrodectus backdoor. Their[...]

This NetworkMiner release brings improved extraction of artifacts like usernames, passwords and hostnames from network traffic. We have also made some updates to the user interface and continued our effort to extract even more details from malware C2 traffic. More Artifacts Extracted Usernames and p[...]

Are you importing indicators of compromise (IOC) in the form of domain names and IP addresses into your SIEM, NDR or IDS? If so, have you considered for how long you should keep looking for those IOCs? An IoT botnet study from 2022 found that 90% of C2 servers had a lifetime of less than 5 days and[...]

I will teach a live online network forensics training on February 23-26. The full title of the class is Network Forensics for Incident Response, where we will analyze PCAP files containing network traffic from hackers and malware. The training is split into four interactive sessions running from 13:[...]

Gh0stKCP is a transport protocol based on KCP, which runs on top of UDP. Gh0stKCP has been used to carry command-and-control (C2) traffic by malware families such as PseudoManuscrypt and ValleyRAT/Winos4.0. @Jane_0sint recently tweeted about ValleyRAT using a new UDP based C2 protocol. I wanted to t[...]