Blow computers - they're naturally dangerous (4,6)

I believe the answer is:

puff adders

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'naturally dangerous' is the definition.
I can't judge whether this defines the answer.

'blow computers' is the wordplay.
'blow' becomes 'puff' (puffing is a kind of blowing).
'computers' becomes 'adders' (I can't explain this - if you can you should believe this answer much more).
'puff'+'adders'='PUFF ADDERS'

'they're' is the link.

Can you help me to learn more?

I've seen this clue in The Globe and Mail.

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