This is the second Economist article to mention the lethal trifecta in the past week - the first was
https://www.economist.com/science-and-technology/2025/09/22/... - which was the clearest explanations I've seen anywhere in the mainstream media about what prompt injection is and why it's such a nasty threat.
(And yeah I got some quotes in it so I may be biased there, but it genuinely is the source I would send executives to in order to understand this.)
I like this new one a lot less. It talks about how LLMs are non-deterministic, making them harder to fix security holes in... but then argues that this puts them in the same category as bridges where the solution is to over-engineer them and plan for tolerances and unpredictability.
While that's true for the general case of building against LLMs, I don't think it's the right answer for security flaws. If your system only falls victim to 1/100 prompt injection attacks... your system is fundamentally insecure, because an attacker will keep on trying variants of attacks until they find one that works.
The way to protect against the lethal trifecta is to cut off one of the legs! If the system doesn't have all three of access to private data, exposure to untrusted instructions and an exfiltration mechanism then the attack doesn't work.
(And yeah I got some quotes in it so I may be biased there, but it genuinely is the source I would send executives to in order to understand this.)
I like this new one a lot less. It talks about how LLMs are non-deterministic, making them harder to fix security holes in... but then argues that this puts them in the same category as bridges where the solution is to over-engineer them and plan for tolerances and unpredictability.
While that's true for the general case of building against LLMs, I don't think it's the right answer for security flaws. If your system only falls victim to 1/100 prompt injection attacks... your system is fundamentally insecure, because an attacker will keep on trying variants of attacks until they find one that works.
The way to protect against the lethal trifecta is to cut off one of the legs! If the system doesn't have all three of access to private data, exposure to untrusted instructions and an exfiltration mechanism then the attack doesn't work.