A Network Allow-List Won't Stop Exfiltration
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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.
Implement an egress proxy with TLS inspection and DNS entropy checks to detect data exfiltration through allowed channels.
For a solutions architect building secure CI/CD pipelines or sandboxed AI agent execution, this highlights a critical blind spot in network policies and a practical L7 DLP approach.
Say you run a piece of untrusted code – an AI-generated script, a dependency’s postinstall hook, a build step from a repo you just cloned – inside a sandbox. You lock it down: no filesystem access outside the working directory, no network except the one domain it legitimately needs, no dangerous syscalls. That stops a lot of bad behavior. It also has a blind spot, and it’s a big one. I ran into this building Canister , a lightweight, unprivileged Linux sandbox – it stacks user namespaces, seccomp, and network isolation to run untrusted commands with minimal privileges, no root and no…