Firecracker
A stripped-down virtual machine technology from AWS, designed with far less to attack than a general-purpose one.
Firecracker is a microVM: a virtual machine that deliberately supports almost nothing. No graphics, no sound, no legacy hardware emulation, just enough to boot a Linux system and talk over the network. AWS built it to run Lambda functions, where you want to start thousands of tiny isolated environments quickly and cheaply.
The security benefit comes from the same choices. Every feature a virtual machine offers is code an attacker can probe, so a general-purpose one like QEMU presents a large surface. When Trail of Bits pointed a cyber-capable AI agent at both in 2026, the agent escaped the general-purpose virtual machine three times and did not escape Firecracker. That does not make it impregnable, only a much harder target.