Coreshell is a hacking tool, which is a part of the large arsenal of malware that the hacking group Fancy Bear employ in its attacks. Fancy bear also is known as APT28 (Advanced Persistent Threat). Their usual targets often include government institutions and military organizations, which has lead many to believe that this notorious hacking group likely has ties to the Kremlin. It is not unheard of governments to employ hacking groups for various shady projects. It is largely believed that the North Korean government is working with another APT called Lazarus (also known as Hidden Cobra) closely, usually on projects involving espionage.
Coreshell is an updated version of Sourface – a Trojan downloader, which has been employed by Fancy Bear in quite a few of their attacks. However, it would appear that they put some serious effort into upping their game because Coreshell is vastly superior to Sourface. Coreshell is much better at detecting whether it has been placed into a sandbox environment and once this is detected it would cease all to evade being dissected and studied by malware researchers. Its capabilities to avoid being detected by anti-virus applications also has been improved. Coreshell is used in the first stage of the attack - it gathers basic system information, and transmits it to the attacker's server. In response, it receives a second-stage payload that is meant to be deployed on the compromised host. The outbound and inbound communication of the Coreshell downloader is secured and encrypted. Usually, Trojan downloaders are programmed to provide the attackers with all sorts of information about the machine they have landed on. Coreshell only shares the most basic information about the system – a list of processes that are being run currently. Then the attackers will send the payload, which is to be executed on the infiltrated machine.
Coreshell is being propagated via spear phishing spam email campaigns, which is a very common method of spreading these threats. It is crucial that government organizations and other large entities educate their employees on the importance of cybersecurity and keep them up-to-date with the best practices in online safety.