In practical O&M (Operations & Maintenance), many security appliances—such as firewalls, IDS/IPS, and Anti-DDoS systems—are deployed in intranet or air-gapped environments. These devices cannot directly connect to the internet to update signature databases or system patches; instead, offline update packages must be downloaded and imported manually. Since vendor download pages are often fragmented or difficult to locate (and frequently require authentication), I have compiled this list of offline update portals for major security vendors to simplify centralized discovery and maintenance. This content will be continuously updated—feel free to bookmark, share, or contribute.