Some people consider 'man' to be gender-neutral but a growing number do not; the OP explicitly said the organization does not. That's why I'm downvoting this answer.

Also from your google link you'll see "man" defined as "an adult male human". Although it has been used neutrally in some ways, it certainly is not a truly neutral word.

The character normally associated with MITM is Mallory

@arp Do you not agree that 'man' has long been well-understood as having both gender-specific and gender-neutral senses?

@WoJ oddly I could find more Eve examples online... anyway added Mallory too!

@Luke I definitely agree that it's not the perfect choice as a neutral word, due to the ambiguity. So the question is, what would be better? 'Monkey in the middle' is fun, but 'monkey' can be deeply offensive in some contexts. 'Person' in the middle seems less allowing of the entity in the middle being an automated actor to me.

What percentage of the people who think 'man' is neutral are men? In any case, this question was framed in terms of a corporate policy which the OP must adhere to.

@arp Your question assumes that 'man' either is or isn't neutral - it's not a question that arises if you understand the word to have both senses. And I've addressed the corporate aspect in my answer.

oddly I could find more Eve examples online The difference between Eve and Mallory is that Eve is just passively listening. This is a kind of MITM attack but often one will try to inject or modify some information, this is where Mallory comes into play. One notable difference is that Eve can do her job without a MITM (just by looking at the mirrored traffic for instance, without interfering). A MITM is always active on teh sense that it breaks the connection and reistates it.

This does not answer the question.

@AzorAhai-him- why do you think that? Happy to clarify where needed.

@topoReinstateMonica It's not unclear - it just doesn't answer the question.

@AzorAhai-him- what matter raised in the OP do you think is not addressed in my answer?

@topoReinstateMonica Of course "man" has both gender-neutral and gender-specific senses. That's precisely why it cannot be used when a gender-neutral word is required -- because even when the word is used as its gender-neutral sense, the gender-specific sense comes along for the ride. The trouble and joy of words with overloaded meanings is that you can (and thus must) expect your reader to receive any and all of them.

@topoReinstateMonica Azor Ahai is probably referring to the question in the headline. It specifically asks for a different phrase than the one you suggest.

@Timbo I think my perspective on this is a little different - I generally expect my reader, where that reader is familiar with the language, to understand in what sense a word is meant.

@topoReinstateMonica I assert that you will become an even better communicator if you understand that your readers will interpret words in senses other than the one you meant -- especially those readers that are more familiar with the language. Write for poets.

@Timbo Won't most people who are familiar with the technical term Man-in-the-middle/MITM see it as something of a fixed phrase?

@Timbo Your points are well made, but equally you could say that it's the fixed mindset that fails to make allowances for the existing nuance and intent of certain words and phrases. "People with a flexible/growth mindset will see it as mutable, and adapt" - sounds great, but I remember an Islamic scholar who was something of an ISIS apologist saying something similar in a TV news interview about the destruction of ancient artworks from cultures they didn't agree with...

Words are ephemeral by nature. Drawing a parallel between a movement to choose more inclusive and respectful words and a movement to destroy artifacts is disingenuous at best.

@Timbo I think one could make a case that most things - certainly cultural ones - are ephemeral by nature. I'm not one to make a case for cultural change being good or bad in general. It will often be seen differently by different groups.

"Man" was gender-neutral 1500 years ago. Nowadays? Not so much. Unless you want to start talking about wífmen and wyrmen, it makes sense to make our decisions on the basis of the modern meaning.

@Adamant No, it’s contextually still pretty gender-neutral. The ones who are arguing it isn’t are usually also the ones who are trying to throw out every fixed phrase in existence that may be remotely perceived as offensive without considering how that may actually impact people’s ability to efficiently communicate.

@Adamant The way I see it, there is still no one, single modern meaning of 'man' - there's a gendered meaning ('he's a man, not a woman'), an exclamatory meaning ('oh man!'), a meaning relating to power or authority ('stick it to the man'), a meaning relating to doing a duty ('man the lifeboats'), and a non-gendered meaning (four man tent)... and probably more.

It might well be that the gender-neutral meaning is fading and will continue to fade, but I don't think it's disappeared yet.

I would expect someone to recommend an alternative company. Neutrality is one thing and professional language is another.