Byer-Nichols Threat Brief for December 16-31 2025

This threat intelligence brief provides a comprehensive analysis of the global cybersecurity landscape during the final two weeks of 2025. It highlights Qilin as the most dominant ransomware threat, noting a specific surge in attacks against the manufacturing sector and small businesses. The report identifies a dangerous shift toward stealthier intrusion methods, such as DNS manipulation and the use of sophisticated backdoors like ToneShell. It also details the active exploitation of network edge devices from major vendors like Fortinet and Cisco. While the summary warns of evolving malware like Cellik and GachiLoader, it concludes with notable defensive victories, including Interpol-led arrests and the successful decryption of multiple ransomware strains.