11/24/2023 0 Comments Ed cobalt strike![]() However, there were only dozens of functions recognized, which is quite a small number relative to its size. After loading it into Binary Ninja, I saw it was not packed or encrypted by any well-known packer or protector. It is an x86 PE binary that is 284kB in size. First ImpressionsĪ friend of mine shared with me this sample (zip password: infected). Much of the effort was spent on fixing the file so it could be loaded by Binary Ninja for further analysis. Initially, I thought this must not be a PE executable at all, but I gradually realized it was. The dropper decrypts, loads, and executes the payload. The payload is a custom executable file format based on DLL. Because of its extensive use of Cobalt Strike across its attacks, Carbanak was also known as CobaltGoblin or the Cobalt Group.In this blog post, I will explain how I reverse engineered a Cobalt Strike dropper and obtained its payload. Carbanak was an umbrella group with different divisions that targeted financial institutions and retailers, stealing hundreds of millions of dollars after lurking inside networks and learning the financial processes and workflows of their victims before initiating money transfers. One of the first cybercriminal gangs to use it extensively was Carbanak. While Cobalt Strike has long been used by APT groups. ![]() Google’s rules include 165 signatures covering 34 different Cobalt Strike versions, each with 10 to 100 attack templates and typically unique Beacon components. Security teams can also use YARA internally to hunt for threats in their networks. YARA is an open-source cross-platform tool for identifying and cataloging malware that’s used and supported by most security vendors. The Google team also released YARA rules on GitHub. We also released these signatures as open source to cybersecurity vendors who are interested in deploying them within their own products, continuing our commitment to improving open source security across the industry.” “We focused on these versions by crafting hundreds of unique signatures that we integrated as a collection of community signatures available in VirusTotal. “The leaked and cracked versions of Cobalt Strike are not the latest versions from Fortra, but are typically at least one release version behind,” researchers with Google’s Cloud Threat Intelligence (GCTI) said in a blog post. This is exactly what the Google researchers had in mind when they began their effort of mapping all versions of Cobalt Strike, complete with their unique files and templates, released since 2012. This creates a detection opportunity because legitimate paying customers are likely to be using the last version of the framework which includes all the latest bug fixes. To avoid paying this price, most attackers who rely on Cobalt Strike use older versions that have been cracked and leaked online. In fact, it’s quite expensive, with a per-user annual license of US$5,900. Unlike other tools, however, Cobalt Strike is not free. Seeing the success of this tactic, many cybercriminal gangs also started to shift their approach from using highly automated malware with self-propagation capabilities that tried to infect as many systems as possible to find a weak entry point for the deployment of a lightweight implant for remote access and then moving laterally manually by using open source network scanners, credential dumpers, legitimate privilege escalation tools, and so on. Security vendors are also reluctant to flag some of these tools as malicious, due to the high risk of false positives. These groups rightly understood that abusing the same tools that IT or security teams commonly use in their work environments will challenge the malware detection and prevention controls that organizations had in place. The use of this tactic, known as living off the land (LOTL), used to be a telltale sign of sophisticated cyberespionage groups who moved laterally through environments using manual hacking and placed great value on stealth. The abuse by attackers of system administration, forensic, or security tools that are either already installed on systems or can be easily deployed without raising suspicion has become extremely common. ![]() ![]() Cobalt Strike is a commercial attack framework designed for red teams that has also been adopted by many threat actors, from APT groups to ransomware gangs and other cybercriminals. Google recently released a list of YARA detection rules for malicious variants of the legitimate Cobalt Strike penetration testing framework that are being used by hackers in the wild.
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