A Network Allow-List Won't Stop Exfiltration
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Summary
A network allow-list cannot stop data exfiltration because attackers can encode secrets in DNS subdomain lookups or HTTP requests to permitted domains. The Canister sandbox addresses this by forcing all outbound TCP through a local HTTPS proxy that performs TLS termination, inspects plaintext, and checks DNS entropy, using seccomp SECCOMP_USER_NOTIF to intercept connect() syscalls. This design is motivated by supply chain attacks like the Shai-Hulud worm that exfiltrated credentials via npm installs.