The attribution to the Lazarus group is based on the similarities with other malware associated with the APT group.
On August 2019, the experts at Intezer and McAfee have conducted a joint investigation focused the analysis on the code reuse, past investigations revealed that some APT groups share portions of code and command and control infrastructure for their malware.
The experts analyzed thousands of malware samples, many still unclassified or uncategorized, and discovered many similarities in the source code used in attacks associated with North Korea.
Recently, experts at Fortinet analyzed some new samples associated with Lazarus noticing that they shared multiple characteristics such as the compilation timestamps spanning from May 4, 2017, to February 13, 2018.
All the samples have the language ID for Korean, they were compiled for 32-bit systems and they were using encrypted strings to make harder the analysis.
Experts noticed that in some cases, the samples reused portions of code such as some functions.
The analysis of the functionality of the malware allowed the experts to determine that it resolves functions dynamically, in fact, the researchers noticed the malicious code invoked only a few APIs. The samples were importing a small number of common DLLs and functions.
For persistence, the RAT inserts itself into a Run registry key, though in some cases it installs itself as a service.
The main functionality of the malware is to provide attackers with remote administration of the infected host.
The NukeSped RAT implements the following features:
The attribution of malware to a specific threat actor is not simple,
“Given all the evidence so far, we can conclude that the NukeSped RATs have some relation to North Korea threat actors (HIDDEN COBRA),” concludes Fortinet.
(SecurityAffairs – NukeSped RAT, North Korea)