Cybersecurity agencies in the U.S. and U.K. are warning about a custom malware called Firestarter persisting on Cisco Firepower and Secure Firewall devices running Adaptive Security Appliance (ASA) or Firepower Threat Defense (FTD) software. [...]

https://www.bleepingcomputer.com/news/security/firestarter-malware-survives-cisco-firewall-updates-security-patches/