Sophos has identified a five-year campaign, dubbed “Pacific Rim”, by Chinese threat actors targeting network appliances, particularly Sophos firewalls. These attackers, including APT31, APT41/Winnti, and a third group, have employed a variety of tactics, including botnets, zero-days, custom malware, firmware backdoors, and UEFI implants, in attempts to compromise these devices. The UEFI implants, while not entirely new, are particularly concerning as they provide attackers with a persistent foothold on the firewall, potentially enabling them to gain control over the entire network. This campaign highlights the vulnerability of network appliances and the increasing sophistication of threat actors. Attackers are exploiting vulnerabilities, utilizing zero-day exploits, and implementing backdoors to gain access to sensitive data and gain a foothold in targeted organizations.